Dissertations / Theses: 'Water use efficiency'

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Sedibe, Moosa Mahmood. "Optimising water use efficiency for crop production." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53541.

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Thesis (MScAgric)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: Poor water management and poor water use efficiency (WUE) have been identified as one of the major problems experienced by vegetable growers in most of the developing countries, including South Africa. This poor management and poor utilization of water have led to a drastic decline in the quality and quantity of available water. In South Africa agriculture uses about 50% of available water. Increasing water demand for domestic, industrial and mining uses, may decrease agriculture's share to less than the current 50%, henceforth, better utilization of this resource is imperative. Selection of a good irrigation system can limit water loss considerably. Some irrigation systems have a potential to save more water than others do. Since irrigation systems affect the WUE of crops, care should be taken when selecting an irrigation system under conditions of limited water quantity. Ebb-and- Flood watering systems have been introduced for effective sub-irrigation and nutrient delivery within closed systems. Such a system was adapted in South Africa, to develop a vegetable production unit for use by families in rural communities, while saving substantial amounts of water. A need to further improve the WUE of this system was subsequently identified. Two studies were conducted at the experimental farm of the University of Stellenbosch (Department of Agronomy). The first trial was conducted under controlled conditions in a glasshouse, and the second under open field conditions. In the first trial, Beta vulgaris (Swiss chard) and Amaranthus spp. ('Imbuya') were grown in two root media; gravel and pumice. In addition, an 'Ebb-and-Flood' and a 'Constant level' system were used with nutrient solutions at two electrical (EC) conductivity levels 1.80 and 3.60 mS cm-I. The results of this (2x2x2x2) factorial experiment indicated that a combination of the 'Ebb-and-Flood' system with gravel as a root medium produced the best results at a low EC, when 'imbuya' was used. A high total WUE was found with 'imbuya', (7.35 g L-I) at EC 1.80 mS cmicompared to a relatively low WUE of 5. 90 g L-I when the 3.60 mS cm-I nutrient solution was used. In the second trial, 'Imbuya's' foliage dry mass, leaf area and WUE was evaluated under field conditions at the Stellenbosch University experimental farm, during the summer of2002. The experimental farm (33°55'S, 18°52'E) is situated in the cooler coastal wine grape-producing region of South Africa with a relatively high annual winter rainfall. This trial was conducted on an alluvial soil, with clay content of 25% and a pH of 5.9 (KC!). A closed 'Ebb-and-Flood' system was compared with two open field irrigation systems ('Drip' and 'Flood') using nutrient solutions at two electrical conductivity levels (1.80 and 3.60 mS cm-i) in all three cases. Foliage dry mass, leaf area as well as WUE was best with 'Drip' irrigation, when a nutrient solution with an electrical conductivity of 3.60 mS cm-i was used. In spite of the fact that additional ground water was available for the soil grown 'Drip' and 'Flood' treatments, the 'Ebb-and-Flood' system outperformed the 'Flood' treatment, especially when the nutrient solution with an EC of 3.6 mS cm-i was used. Insufficient root aeration in the flooded soil could have been a contributing factor. The fact that the 'Ebb-and-Flood' and 'Drip' systems gave the best results when the high EC solution was used to fertigate the plants, may indicate that the plants could have hardened due to the mild EC stress, better preparing them to adapt to the extreme heat that was experienced in the field.
AFRIKAANSE OPSOMMING: Swak: bestuur van water en 'n swak: water-gebruik-doeltreffendheid (WOD) is as een van die belangrikste probleme geïdentifiseer wat deur groente produsente in die meeste ontwikkelende lande, insluitend Suid-Afrika, ervaar word. Hierdie swak bestuur en benutting van water het daartoe bygedra dat 'n drastiese afname in die kwaliteit asook in die kwantiteit van beskikbare water ervaar word. In Suid-Afrika gebruik die landbou-sektor ongeveer 50% van die beskikbare water. Toenemende water behoeftes vir huisgebruik, industrieë en die mynbou mag hierdie 50% aandeel van die landbou sektor laat krimp. Beter benutting van hierdie skaars hulpbron is dus noodsaaklik. Die keuse van goeie besproeiingsisteme mag waterverliese merkbaar beperk aangesien sekere sisteme se water-besparingspotensiaal beter as ander is. Aangesien besproeiingstelsels die WOD van gewasse beïnvloed, is spesiale sorg nodig waar 'n besproeiingstelsel onder hierdie toestande van beperkte waterbronne gekies moet word. 'Ebb-en-Vloed' sisteme kan aangewend word om water en voedingselemente van onder in 'n wortelmedium te laat opstoot en in 'n geslote sisteem te laat terugdreineer. So 'n sisteem is in Suid-Afrika ontwikkel waarmee groente vir families in landelike gebiede geproduseer kan word terwyl water bespaar word. 'n Behoefte om die WOD van hierdie produksiesisteem verder te verbeter is egter geïdentifiseer. Twee ondersoeke is by die Universiteit van Stellenbosch se proefplaas (Departement Agronomie) gedoen. Die eerste proef is onder beheerde omgewingstoestande in 'n glashuis uitgevoer en die tweede onder veld toestande. In die eerste proef is Beta vulgaris (Snybeet) en Amaranthus spp. ('Imbuya') in twee tipes wortelmedia; gruis en puimsteen verbou. 'n 'Ebb-en-Vloed' asoook 'n 'Konstante vlak' besproeiingsisteem is gebruik terwyl voedingsoplossings ook by twee peile van elektriese geleiding (EC) teen 1.80 en 3.60 mS cm-I toegedien is. Die resultate van hierdie (2x2x2x2) fakroriaal eksperiment het aangetoon dat 'n kombinasie van die 'Ebb-en-Vloed' sisteem met gruis as 'n wortelmedium die beste resultate teen 'n lae EC lewer waar 'imbuya' gebruik is. Die WOD met 'imbuya' was hoog (7.35 g L-1) by 'n EC van 1.80 mS cm-I, vergeleke met 'n relatief lae WOD van 5. 90 g L-1 waar die 3.60 mS cm-I voedingsoplossing gebruik is. In die tweede proef is 'Imbuya' se droë blaarmassa, blaar oppervlakte en WOD onder veldtoestande op die Universiteit van Stellenbsoch se proefplaas in die somer van 2002 ge-evalueer. Die proefplaas (33°55'S, 18°52'E) is in die koeler kusstreke van die wyndruif produksiegebied in die winterreëngebied van Suid-Afrika geleë. Hierdie proef is op alluviale grond met 25% klei en 'n pH van 5.9 (KCi) uitgevoer. 'n Geslote 'Ebb-en-Vloed' sisteem is met twee veld-besproeiingsisteme vergelyk ('Drup' en 'Vloed') terwyl voedingsoplossings teen twee peile van elektriese geleiding (1.80 en 3.60 mS cm-I) in al drie gevalle gebruik is. Blaar droëmassa, blaaroppervlakte asook die WGD was die beste met 'Drup' besproeiing waar die EC van die voedingsoplossing 3.60 mS cm-I was. Ten spyte van die feit dat ekstra grondwater vir die 'Drup' and 'Vloed' behandelings beskikbaar was, het die 'Ebben- Vloed' stelsel beter as die 'Vloed' behandeling gedoen veral waar die voedingsoplossing se EC 3.6 mS cm-I was. Swak wortelbelugting was waarskynlik die rede waarom vloedbesproeiing swak produksie gelewer het. Die feit dat die 'Drup' en die 'Ebb-en-Vloed' behandelings in die veldproef die beste gedoen het waar die EC hoog was, mag moontlik met die gehardheid van die plante verband hou wat aan ekstreem warm en dor toestande blootgestel was.

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Morgado, dos Santos Ana Maria. "Plant factors influencing water use efficiency of wheat." Thesis, University of Reading, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434315.

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Adiredjo, Afifuddin Latif. "Water use efficiency in sunflower : Ecophysiological and genetic approaches." Phd thesis, Toulouse, INPT, 2014. http://oatao.univ-toulouse.fr/20177/1/adiredjo.pdf.

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Water use efficiency (WUE), measured as the ratio of plant biomass to water consumption, is an essential agronomical trait for enhancing crop production under drought. Measuring water consumption is logistically difficult, especially in field conditions. The general objective of the present Thesis is to respond to three main questions: (i) can WUE be determined by using carbon isotope discrimination (CID), easy to measure?, (ii) how WUE and CID variation analysis can contribute to the genotypic selection of sunflower subjected to drought?, and (iii) can WUE variation be revealed by the variation of plant-water relation traits. Four experiments were carried out in greenhouse across two different years: (i) on two drought scenarios, progressive soil drying and stable water-stress, and (ii) on five levels of soil water content. The main traits that have been measured include WUE, CID, as well as plant-water relation traits, i.e. control of transpiration (FTSWt), water extraction capacity (TTSW), and dehydration tolerance (OA). A highly significant negative correlation was observed between WUE and CID, and a wide phenotypic variability was observed for both WUE and CID. A wide variability was also observed for FTSWt, TTSW and OA. The results provide new insight into the genetic control of WUE and CID related-traits, which, unlike to other crops, genetic control of WUE, CID, and TTSW in sunflower have never been reported in the literature. Further, quantitative trait loci (QTL) mapping for FTSWt was never reported in any plant species. The QTL for WUE and CID were identified across different drought scenarios. The QTL for CID is considered as a ‘‘constitutive’’ QTL, because it is consistently detected across different drought scenarios. The QTL for CID co-localized with the QTL for WUE, biomass and cumulative water transpired. Co-localization was also observed between the QTL for FTSWt and TTSW, between the QTL for TTSW and WUE-CID-biomass, as well as between the QTL for FTSWt-TTSW and biomass. This study highlights that WUE is physiologically and genetically associated with CID. CID is an excellent surrogate for WUE measurement, and can be used to improve WUE by using marker-assisted selection (MAS) to achieve the ultimate goal of plant breeding at genomic level.

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Tomás, Mir Magdalena. "Physiological mechanisms involved in water use efficiency in grapevines." Doctoral thesis, Universitat de les Illes Balears, 2012. http://hdl.handle.net/10803/84126.

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La sequera és una de les majors limitacions per a l’agricultura en general, factor que pot incrementar d’acord amb les prediccions del canvi climàtic. Per això, reduir l’ús de l’aigua en el reg i augmentar l’eficiència en l’ús de l’aigua (EUA) constitueix una de les majors prioritats per aconseguir una agricultura sostenible. L’EUA és un balanç entre guanys de biomassa i les despeses d’aigua. Aquesta Tesi s’ha centrat en l’estudi de 3 dels processos fisiològics que afecten a l’ús de l’aigua i a la producció de la planta en el cas de la vinya, i que per tant poden ser considerats factors potencials per millorar l’EUA: (1) conductància del mesòfil, (2) transpiració nocturna (3) respiració. Els resultats d’aquesta Tesi revelen que la conductància del mesòfil i la respiració són els principals components per millorar l’EUA permetent millorar l’assimilació de carboni o minimitzant les pèrdues del carboni fixat per la fotosíntesis

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Tonmukayakul, Nop. "Water use efficiency of six dryland pastures in Canterbury." Lincoln University, 2009. http://hdl.handle.net/10182/1498.

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The annual and seasonal water use efficiency of six pasture combinations were calculated from the ‘MaxClover’ Grazing Experiment at Lincoln University. Pastures have been established for six years and are grazed by best management practices for each combination. Measurements for this study are from individual plots of four replicates of ryegrass (RG)/white clover (Wc), cocksfoot (CF)/Wc; CF/balansa (Bal) clover; CF/Caucasian (Cc) clover; CF/subterranean (Sub) clover or lucerne. Water extraction measurements showed soils for all dryland pastures had a similar plant available water content of 280±19.8 mm. Dry matter measurements of yield, botanical composition and herbage quality were assessed from 1 July 2008 until 30 June 2009. Lucerne had the highest annual yield of 14260 kg DM/ha/y followed by the CF/Sub at 9390 kg DM/ha/y and the other grass based pastures at ≤ 6900 kg DM/ha/y. All pastures used about 670±24.4 mm/y of water for growth. Lucerne had the highest annual water use efficiency (WUE) of 21 kg DM/ha/mm/y of water used (total yield/total WU). The WUE of CF/Sub was the second highest at 15 kg DM/ha/mm/y, and the lowest was CF/Wc at 9 kg DM/ha/mm/y. The CF/Sub pastures had the highest total legume content of all grass based pastures at 21% and as a consequence had the highest annual nitrogen yield of 190 kg N/ha. This was lower than the monoculture of lucerne (470 kg N/ha). Ryegrass/white clover had the highest total weed component in all pastures of 61%. For dryland farmers spring is vital for animal production when soil temperatures are rising and moisture levels are high. The water use efficiency at this time is important to maximize pasture production. In spring lucerne produced 8730 kg DM/ha, which was the highest dry matter yield of all pastures. The CF/Sub produced the second highest yield of 6100 kg/DM/ha. When calculated against thermal time, CF/Sub grew 5.9 kg DM/ºCd compared with lucerne at 4.9 kg DM/ºCd. The higher DM yield from lucerne was from an extra 400 ºCd of growth. The highest seasonal WUE of all pastures occurred in the spring growing period. Linear regressions forced through the origin, showed lucerne (1/7/08-4/12/08) had a WUE of 30 kg DM/ha/mm (R2=0.98). Of the grass based pastures, CF/Sub produced 18 kg DM/ha/mm (R2=0.98) from 1/7 to 10/11/08 from 270 mm of water used. The lowest spring WUE was 13.5 kg DM/ha/mm by CF/Bal pastures which was comparable to the 14.3±1.42 kg DM/ha/mm WUE of CF/Wc, CF/Cc and RG/Wc pastures. During the spring, CF/Sub clover had the highest spring legume component of the grass based pastures at 42% and produced 120 kg N/ha. This was lower than the 288 kg N/ha from the monoculture of lucerne. Sub clover was the most successful clover which persisted with the cocksfoot. Based on the results from this study dryland farmers should be encouraged to maximize the potential of lucerne on farm, use cocksfoot as the main grass species for persistence, rather than perennial ryegrass, and use subterranean clover as the main legume species in cocksfoot based pastures. By increasing the proportion of legume grown the water use efficiency of a pasture can be improved. When pastures are nitrogen deficient the use of inorganic nitrogen may also improve pasture yields particularly in spring.

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Bernier, Marie-Hélène. "Assessing on-farm water use efficiency in southern Ontario." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32251.

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Assessing On-Farm Irrigation Water Use Efficiency in Southern Ontario In southern Ontario, irrigation is essential for high value horticultural crop production to overcome insufficient rainfall and achieve stabilized crop production. In a context where competition for limited water resources intensifies due to the expansion of the agricultural sector, increasing urban development and tourism, and potential climate change impacts, conserving water through efficient irrigation has become a key solution to address this growing challenge. The implementation of advanced soil water monitoring technologies and water budgeting for improved irrigation scheduling is explored to conserve water and thus cope with increasing competing demands for limited water supplies. Soil moisture was measured by gravimetric sampling in conjunction with several modern soil water sensors over the course of the 2007 growing season at 15 field sites located in southern Ontario where high value horticultural crop production is predominant. Quantities of irrigation water used were measured by flow meters that were installed at three of these sites. In addition, two grower surveys were administered: the first to collect information on current irrigation scheduling practices, and another to determine the appropriateness of the soil moisture monitoring sensors. On-farm irrigation performance was assessed by comparing calculated crop water requirements (using the water budget method) with growers' estimates of irrigation water use with soil moisture measurements taken during the growing season. In five out of six experimental zones, water was either excessively or insufficiently applied. In
Évaluation de l'Efficacité d'Utilisation de l'Eau d'Irrigation à l'Échelle de la Ferme dans le Sud de l'Ontario Dans le sud de l'Ontario, l'irrigation est essentielle à la production de cultures horticoles à haute valeur ajoutée afin de compenser l'insuffisance de précipitations et stabiliser la production de cultures. Dans un contexte où la compétition pour les ressources limitées en eau s'intensifie en réponse à l'expansion du secteur agricole, à la croissance du développement urbain et du tourisme, ainsi qu'aux impacts potentiels des changements climatiques, conserver l'eau grâce à des techniques d'irrigation économes est devenue une solution incontournable pour affronter ce défi grandissant. L'implémentation de technologies avancées de surveillance de la teneur en eau dans le sol et d'un bilan hydrique, pour améliorer les pratiques d'irrigation programmée, est explorée afin de conserver l'eau et ainsi mieux faire face à l'augmentation concurrentielle des demandes pour les ressources limitées en eau. Au cours de la saison de croissance de 2007, l'humidité du sol a été mesurée avec plusieurs sondes ainsi que par la méthode gravimétrique pour quinze sites situés dans le sud de l'Ontario où la production de cultures à haute valeur ajoutée est prédominante. Les quantités d'eau utilisées pour irriguer étaient mesurées par des compteurs de débit installés dans trois des quatre sites. De plus, les producteurs ont répondus à deux questionnaires: le premier visant à recueillir l'information concernant des pratiques actuelles d'irrigation programmée et le second à déterminer l'utilité des sondes mesurant l'humidité du sol. La

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Wynn, Paul Laurence. "Water use efficiency and drought resistance in ornamental plants." Thesis, The University of Sydney, 2009. https://hdl.handle.net/2123/28220.

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Increasing concerns over the distribution, abundance and security of fresh water resources in Australia have led to a nationwide re—evaluation of their management and sustainability. The potential for reductions in municipal water use through demand management are substantial, including the potential for savings through the improved design and management of the irrigated urban landscape. It is proposed that the selection of more appropriate plant species is essential to maximising outdoor water savings. Current plant selection practices are, however, typically based upon highly questionable and potentially flawed anecdotal evidence. Ideally, these decisions should stem from detailed investigation of the water requirements, drought tolerance and water use efficiency (WUE) of specific plants. Such investigation forms the basis of this thesis. An extensive range of ornamental plant species were therefore examined, chosen based on their origin (native vs. exotic) and aesthetic function or utility in the landscape. It was hypothesised that those plants of Australian origin, due to the frequency of drought in their native habitats, would demonstrate more tolerance to water stress than their exotic counterparts. In the first of three experiments, plants were subjected to varying levels of drought stress using differential rates of irrigation, each replacing a fixed percentage of potential evapotranspirational demand. Plant recovery capacity was subsequently assessed during an extended well—watered period. A range of physiological parameters was monitored and, using digital image analysis, changes in the level of foliar display and canopy transparency were assessed as objective measures of plant ornamentality and amenity value. Development of an improved method of imposing drought stress, for use in a subsequent study, involved a separate detailed assessment of a high molecular weight polymer, polydiallyldimethylammonium chloride (PDADMAC), which demonstrated its significant potential as an osmoticum. A detailed and intensively monitored third experiment was carried out with two groundcover species, the exotic Lobularia maritima (Sweet Alyssum) and the Australian native Chrysocephalum apiculatum (Yellow Buttons), each previously revealed as having particularly high WUE and drought tolerance. Each species was subjected to one of several rates of drought stress imposition using frequent incremental additions of PDADMAC to an air-lift irrigation system followed by a period of recovery. A similar range of physiological parameters was monitored in this study, in addition to carbon isotope discrimination measurement and a microscopic examination of leaf surface morphology. There was a high level of concurrence between the studies, with the plants of Australian origin generally exhibiting superior drought resistance and higher WUE than the exotic plants examined. The native plants typically maintained higher levels of foliar display and exhibited higher net photosynthesis rates, transpiration rates and final shoot dry weights than the corresponding exotics. The natives also maintained lower overall leaf water potentials, both in the absence and presence of drought stress, possibly enabling the positive water balance in plant tissues through the creation of a strong water potential gradient between plant and soil. C. apiculatum appears to have utilised other traits and strategies for its superior performance under drought stress, including its contrasting phenology to L. maritima and its greater level of pubescence. During recovery, the natives also demonstrated a greater overall capacity for regeneration than the exotics, as measured by foliar gains. The effect of decreasing water availability was also highly consistent across the studies, with decreasing water availability producing overall declines in foliar display, foliar display—based WUE, net photosynthesis rates, leaf water potentials, final shoot dry weights, survival times and general plant health. Based upon the implications of these findings, a number of practical recommendations were developed for use in the design and management of water conserving urban landscapes.

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Bynum, Joshua Brian. "Physiological applications for determining water use efficiency among cotton genotypes." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2635.

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Ogola, J. B. Ochanda. "Improving water use efficiency of maize through proper nitrogen management." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340024.

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Movahedi, Mahsa. "Identifying stomatal signalling genes to improve plant water use efficiency." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4539/.

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Water is lost from higher plants via transpiration through stomatal pores the aperture of which is regulated by pairs of guard cells. Genetic engineering of the guard cell abscisic acid (ABA) signalling network that induces stomatal closure under drought stress is a key target for improving crop water use efficiency. In this study experiments were designed to investigate whether the biochemical mechanisms associated with the N-end rule pathway of targeted proteolysis could be involved in the regulation of stomatal apertures. The results indicate that the gene encoding the plant N-recognin, PRT6 (PROTEOLYSIS6), and the N-end rule pathway, are important in regulating stomatal ABA-responses in addition to their previously described roles in germination and hypoxia. Direct measurements of stomatal apertures showed that plants lacking PRT6 exhibit hypersensitive stomatal closure in response to ABA, and IR thermal imaging revealed reduced evapotranspiration under drought-stress. Together with a reduction in stomatal density, these properties result in drought tolerant plants. Plants lacking PRT6 are able to synthesis NO but their stomata do not close in response to NO suggesting that PRT6 is required for stomatal aperture responses to NO. Double mutant studies suggested that PRT6 (and by implication the N-end rule pathway) genetically interacts with known guard cell ABA signalling components OST1 and ABI1, and that it may act either downstream in the same signalling pathway or in an independent pathway. Several other enzymatic components of the plant N-end rule pathway were also shown to be involved in controlling stomatal ABA sensitivity including arginyl transferase and methionine amino peptidase activities. These results indicate that at least one of the N-end rule protein substrates which mediates ABA sensitivity has a methionine-cysteine motif at its N-terminus. A separate set of experiments were designed to investigate whether stomatal ABA-signalling pathways could have been conserved throughout land plant evolution. Cross-genetic complementation experiments were carried out to determine whether Physcomitrella stomatal apertures are able to respond to ABA and CO2 using a similar signalling pathway to that of flowering plants. The results demonstrated involvement of OST1 and ABI1 orthologues indicating that the stomata of the moss respond to ABA and CO2 using a signalling pathway that appears to be directly comparable to that of the model flowering plant Arabidopsis thaliana.

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Guerra, Elisa <1982&gt. "New water use efficiency strategies to cope with climate change." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5947/1/Guerra_Elisa_Tesi.pdf.

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Crop water requirements are important elements for food production, especially in arid and semiarid regions. These regions are experience increasing population growth and less water for agriculture, which amplifies the need for more efficient irrigation. Improved water use efficiency is needed to produce more food while conserving water as a limited natural resource. Evaporation (E) from bare soil and Transpiration (T) from plants is considered a critical part of the global water cycle and, in recent decades, climate change could lead to increased E and T. Because energy is required to break hydrogen bonds and vaporize water, water and energy balances are closely connected. The soil water balance is also linked with water vapour losses to evapotranspiration (ET) that are dependent mainly on energy balance at the Earth’s surface. This work addresses the role of evapotranspiration for water use efficiency by developing a mathematical model that improves the accuracy of crop evapotranspiration calculation; accounting for the effects of weather conditions, e.g., wind speed and humidity, on crop coefficients, which relates crop evapotranspiration to reference evapotranspiration. The ability to partition ET into Evaporation and Transpiration components will help irrigation managers to find ways to improve water use efficiency by decreasing the ratio of evaporation to transpiration. The developed crop coefficient model will improve both irrigation scheduling and water resources planning in response to future climate change, which can improve world food production and water use efficiency in agriculture.

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Guerra, Elisa <1982&gt. "New water use efficiency strategies to cope with climate change." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5947/.

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Crop water requirements are important elements for food production, especially in arid and semiarid regions. These regions are experience increasing population growth and less water for agriculture, which amplifies the need for more efficient irrigation. Improved water use efficiency is needed to produce more food while conserving water as a limited natural resource. Evaporation (E) from bare soil and Transpiration (T) from plants is considered a critical part of the global water cycle and, in recent decades, climate change could lead to increased E and T. Because energy is required to break hydrogen bonds and vaporize water, water and energy balances are closely connected. The soil water balance is also linked with water vapour losses to evapotranspiration (ET) that are dependent mainly on energy balance at the Earth’s surface. This work addresses the role of evapotranspiration for water use efficiency by developing a mathematical model that improves the accuracy of crop evapotranspiration calculation; accounting for the effects of weather conditions, e.g., wind speed and humidity, on crop coefficients, which relates crop evapotranspiration to reference evapotranspiration. The ability to partition ET into Evaporation and Transpiration components will help irrigation managers to find ways to improve water use efficiency by decreasing the ratio of evaporation to transpiration. The developed crop coefficient model will improve both irrigation scheduling and water resources planning in response to future climate change, which can improve world food production and water use efficiency in agriculture.

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Pointeau, Virginie M. "Water-use efficiency and productivity in native Canadian populations of Populus trichocarpa and Populus balsamifera." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/587.

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Afforestation and reforestation programs utilizing available fields for biofuel production, carbon sequestration, and other uses linked to climate change are looking to tree physiologists to identify species and genotypes best-suited to their purposes. The ideal poplar genotype for use in Canadian programs would be drought-resistant, cold-climate adapted, and fast-growing, thus requiring an understanding of links between a variety of physiological traits linked to growth and productivity. This study examined the basis for variations in water-use efficiency within four selected populations of Populus trichocarpa and Populus balsamifera (2 provenances each). Each species included both a northern and a southern provenance. Correlations between water-use efficiency, nitrogen-use efficiency, ¹³C/¹²C isotope ratio, stomatal conductance, and overall productivity were evaluated. Gas exchange variables measured included net photosynthesis, transpiration rate, stomatal conductance, and intercellular CO₂ content. Water-use efficiency and ¹³C content across all genotypes were highly correlated. Results suggested that variation in water-use efficiency was primarily related to variation in stomatal conductance across all genotypes. Whereas differences in net photosynthesis in this study were not significant between species, P. balsamifera did reveal a higher average stem volume overall. Although variation in stomatal conductance was the major determinant of differences in water-use efficiency, positive correlations were found between ¹³C isotope abundance and net photosynthesis in both P. balsamifera provenances. In this regard, results for the northern P. balsamifera provenance are the most consistent across all gas-exchange and growth trait correlations, in terms of meeting expectations for sink-driven water-use efficiency. The findings in this study suggest the possibility of identifying poplar genotypes with an absence of trade-off between water-use efficiency and nitrogen-use efficiency, notably among genotypes from the northern P. balsamifera provenance, near Gillam.

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Singh, Ajay. "Water and nitrogen use efficiency of corn (Zea mays L.) under water table management." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116989.

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Drainage and water table management are essential for crop production in humid regions. Water table management not only increases crop yield, but also reduces nitrate leaching to water bodies. This study investigated the water and nitrogen use efficiency of corn under two water management conditions and three nitrogen fertilizer levels. The sap flow heat balance method was used to measure the daily water uptake of corn, over an extended period of the growing season. The impacts of climate change on grain corn and biomass yield in eastern Canada under tile drained conditions was also evaluated over a 30 year future period (2040 to 2069). The study was conducted at a field scale in 2008 and 2009 at St. Emmanuel, Quebec. The two water management conditions were: conventional drainage (FD), and controlled drainage with subirrigation (CD-SI). The three nitrogen (N) fertilizer treatments (low, medium, and high N) were applied in a strip across three blocks. The seasonal water balance indicated that the plants in the CD-SI plots had more water than required in the wet periods, despite the system automation, while the FD plots exhibited deficit water conditions. Water could be saved in the wet periods by better regulating water supplied by subirrigation. However, in dry years, the CD-SI system increased yield. The grain corn water use efficiency (WUE) for FD plots was 2.49 and 2.46 kg m-3, in 2008 and 2009, respectively. In these years, the grain WUE for CD-SI plots was 2.43 and 2.26 kg m-3. Water management treatments demonstrated significant difference (p < 0.05) in grain yields in 2009, at low and high nitrogen levels. However, at the medium nitrogen level, water management demonstrated no significant effect (p > 0.05) on grain yields. The two water treatments had no effect on the above-ground dry biomass yields in both years. Mean nitrogen use efficiency (NUE) of grain corn and biomass varied from 27 to 99 kg kg-1. Highest NUE (99 kg kg-1) was observed under low N (~120 kg N ha-1) and lowest NUE (41 kg kg-1) occurred in the high N (~260 kg N ha-1). This might be due to higher nitrogen losses due to leaching, residual nitrogen in the soil, and more denitrification in high N plots. The rate of plant water uptake measured by the sap flow method, varied from 3.55 to 5.11 mm d-1 from silking to full dent stage of corn growth. These rates were consistent with ETc calculated by the FAO-56 Penman-Monteith method (3.70 to 5.93 mm d-1) for both years. Although, silking is considered as a critical stage for corn growth, water demand was highest at the milk stage (45.63 to 59.80 mm). Transpiration during this stage constituted 10 to12% of the total water requirement of the corn for the season. The silking to full dent stage accounted for approximately 40% of the total water requirement of the crop. The STICS (JavaStics v1.0) crop model was used to examine the impacts of climate change, under the B1 emissions scenario, on corn yield from 2040-2069. The model was calibrated using 2008 field measured data, and then validated using the 2009 data set. Corn grain yield was underestimated by 1.5 to 2.6 Mg ha-1 for the two years of measurement. Total dry biomass was also underestimated by 0.9 to 2.6 Mg ha-1. Simulations for the B1 emissions scenario using synthetic weather data was run under the same crop conditions as in 2008. Tukey's studentized range (HSD) test of corn grain yield indicated that yields at high and low N, and high and medium N were different at the 95% confidence level. Grain and biomass production from 2040-2069 under B1 emissions scenario responded differently (p < 0.05) for the three N treatments. However, the Mann–Kendall test showed neither increasing nor decreasing trend (MK-stat > - 1.96) at a 95% confidence level.
Le drainage et la gestion de la nappe phréatique des parcelles agricoles permet non seulement d'augmenter la production des récoltes, mais aussi de réduire les pertes de nitrates par lessivage, qui contribue à leurs transferts vers les étendues d'eau. Cette étude a examiné l'efficacité d'utilisation de l'eau et de l'azote du maïs grain sous deux conditions de gestion de l'eau et trois niveaux d'application d'azote. Les facteurs climatiques jouent un rôle important dans la production du maïs-grain. Les impacts des changements climatiques sur les projections de maïs-grain et de la production de biomasse en sol drainé ont aussi été évalués pour l'est du Canada pour une période futur de 30 ans (2040 à 2069). L'étude a été accomplie à l'échelle du champ en 2008 et en 2009 à Saint Emmanuel au Québec. Les deux scénarios de gestion de l'eau étaient (a) le drainage conventionnel (FD) et (b) le drainage contrôlé combiné à l'irrigation souterraine (CD-SI). Les trois traitements d'azote (N) (dose faible, moyenne et élevée) ont été appliqués en bande sur trois blocs. L'efficacité d'utilisation de l'eau du maïs (WUE) pour les blocs en FD était de 2.49 kg m-3 et 2.46 kg m-3 en 2008 et 2009 respectivement. Pour ces années, L'WUE du maïs-grain pour les blocs en CD-SI était de 2.43 kg m-3 et de 2.26 kg m-3. Les traitements relatifs à la gestion de l'eau ont permis d'améliorer la production de rendement du maïs-grain significativement (p <0.05) en 2009, que cela soit avec des doses d'azotes basses ou élevées. Cependant, pour des doses intermédiaires, la gestion de l'eau n'a démontré aucun effet significatif (p> 0.05) sur les productions de maïs-grain. Les deux traitements relatifs à la gestion de l'eau n'ont eu aucun effet sur la production de biomasse sèche au-dessus du sol pour les deux années. L'efficacité moyenne de l'utilisation de l'azote (NUE) du maïs grain et de sa biomasse variait de 27 kg kg-1 à 99 kg kg-1. La plus haute NUE (99 kg kg-1) a été observée pour une dose de N faible (~120 kg N ha-1). La plus basse NUE (41 kg kg-1) s'est produite pour une dose de N élevée (~260 kg N ha-1). La consommation des plantes en eau mesurée par la méthode d'écoulement de la sève, vari de 3.55 mm d-1 à 5.11 mm d-1 pour la période de l'apparition des soies jusqu'à la croissance complète du maïs-grain. Ces taux sont en accord avec l'ETc calculée (3.70 mm d-1 à 5.93 mm d-1) pour les deux ans. Bien que, le développement de la soie soit considéré comme le stade critique pour le maïs-grain, la demande en eau fut la plus élevée lors du stade laiteux du développement du maïs (45.63 mm à 59.80 mm). À ce stade, 10 à 12% des besoins totaux de la plante en eau pour la saison furent transpirés. Du stade de la soie jusqu'au développement complet de l'épi de maïs les besoins en eau de la plante ont représenté environ 40 % de son besoin total. Le modèle de récolte STICS (JavaStics v1.0) a été utilisé pour examiner les effets du changement climatique sur la production de maïs- grain, de 2040 à 2069 et sous le scénario d'émissions de gaz à effet de serre B1. Le modèle a d'abord été calibré en utilisant les données mesurées au champ en 2008 et, a ensuite été validé avec l'ensemble des données de 2009. La production de maïs-grain est sous-estimée de 1.5 Mg ha-1 à 2.6 Mg ha-1 pour les deux ans de mesure. La biomasse sèche totale est aussi sous-estimée de 0.9 Mg ha-1 à 2.6 Mg ha-1. Les simulations pour le scénario d'émissions B1 en utilisant des données météorologiques synthétiques font été utilisées dans les mêmes conditions de récolte que 2008. Les prédictions de la production de maïs-grain et de sa biomasse pour la période 2040-2069 sous le scénario d'émissions B1 sont différentes (p <0.05) selon les trois traitements de N. Cependant, l'épreuve de Mann-Kendall n'a montré aucune tendance à la hausse ou à la baisse (MK-stat> - 1.96) pour un niveau de confiance de 95%.

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Narayanan, Sruthi. "Canopy architecture and water productivity in sorghum." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/8760.

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Master of Science
Department of Agronomy
Robert M. Aiken
Increasing crop water use efficiency (WUE), the amount of biomass produced per unit water consumed, can enhance crop productivity and yield potential. The objective of the first study was to evaluate the factors affecting water productivity among eight sorghum (Sorghum bicolor (L.) Moench) genotypes, which differ in canopy architecture. Sorghum genotypes, grown under field conditions, showed significant differences in (a) biomass production, (b) water use, (c) intercepted radiation, (d) water productivity and (e) radiation use efficiency (RUE; the amount of biomass produced per unit of intercepted radiation which is suitable for photosynthesis). WUE and RUE were more strongly correlated to biomass production than to water use or intercepted radiation, respectively. RUE was positively correlated to WUE and tended to increase with internode length, the parameter used to characterize canopy architecture. These results demonstrate that increased utilization of radiation can increase water productivity in plants. Sorghum canopies that increase light transmission to mid−canopy leaves can increase RUE and also have the potential to increase crop productivity and WUE. The objective of the second study was to develop a quantitative model to predict leaf area index (LAI), a common quantification of canopy architecture, for sorghum from emergence to flag leaf stage. LAI was calculated from an algorithm developed to consider area of mature leaves (leaves with a ligule/collar), area of expanding leaves (leaves without a ligule/collar), total leaf area per plant and plant population. Slope of regression of modeled LAI on observed LAI varied for photoperiod sensitive (PPS) and insensitive (non−PPS) genotypes in 2010. A good correlation was found between the modeled and observed LAI with coefficient of determination (R[superscript]2) 0.96 in 2009 and 0.94 (non−PPS) and 0.88 (PPS) in 2010. These studies suggest that canopy architecture has prominent influence on water productivity of crops and quantification of canopy architecture through an LAI simulation model has potential in understanding RUE, WUE and crop productivity.

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Hamdani, Anber. "The genetic and physiological basis of water use efficiency in tomatoes." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/18642.

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Drought and heat stress are the major abiotic constraints to plant survival and productivity. This study focused on the estimation of genetic variability in response to water deficit conditions, evaluated the use of carbon isotopes to measure water use efficiency (WUE), and identified SNP marker associations with traits linked to higher genotypic performance under water deficit stress. The diverse plant materials were subjected to two irrigation regimes in two planting seasons and characterized for various morphological and fruit quality traits to explain the genetic variance. The study suggests fruit length to diameter ratio, number of fruits and fruit setting should be considered for selection under water deficit environments. The accessions were genotyped using SNPs to identify marker trait associations (MTAs) under water deficit conditions. About 20% markers were found to be significantly associated with the various traits. Being growth condition specific, these MTAs will need to be validated in a wider set of materials and environments. A subset including six genotypes was used to investigate WUE under controlled conditions at Purdue University, West Lafayette. The WUE was assessed using gravimetric measurements, leaf isotopic composition and diurnal gas exchange measurements. Strong association among ∆13C and other traits including assimilated weighted average intracellular CO2 concentration, intrinsic and instantaneous WUE under varied water deficit levels was observed. The results demonstrated the efficacy of carbon isotopes in predicting changes in WUE as well as substantial variation in WUE among Solanum lycopersicum accessions. The information generated from the present study will advance knowledge to understand the genetic, physiological, and fruit quality response under water deficit stress conditions and help tomato industry develop better adapted tomato genotypes.

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Hoolohan, Claire. "Reframing water efficiency : towards interventions that reconfigure the shared and collective aspects of everyday water use." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/reframing-water-efficiency-towards-interventions-that-reconfigure-the-shared-and-collective-aspects-of-everyday-water-use(9051041e-e89b-43e5-888a-f41ad9d4c926).html.

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This is a thesis about water efficiency, a particular set of practices in the water industry of England and Wales designed to reduce end-use water demand in homes and businesses. Broadly, the thesis aims to understand how water efficiency activities organised and funded by water companies might more effectively support the development of sustainable patterns of domestic demand, in order to contribute to long-term sustainable water management. To achieve this aim, mixed qualitative methods are used to; a) evaluate the extent to which two non-conventional water efficiency activities engage with the collective elements of everyday consumption that existing research deems necessary to steer demand (Strengers, 2012, Macrorie et al., 2014, Shove, 2014, Geels et al., 2015); b) develop a conceptual understanding of demand management as a professional practice, to understand how Water Company activities are shaped, sustained and stifled; and c) develop an understanding of what future water efficiency activities might look like that take account of the findings from this research. Central to this research and analysis is the notion of 'collective', a term that denotes a conceptual perspective on demand that departs from a focus on individuals, towards the shared social, technological and natural relations that structure everyday activity (Browne et al., 2014). The analysis uses this notion of collectives to examine the impacts and limitations of Save Water Swindon, a large-scale 'whole-town' approach to water efficiency (Case Study 1); to explore how Care for the Kennet contributes to demand management by reconfiguring relations between water in the home and water in the river (Case Study 2); and to uncover the collective context of the professional practices of managing demand (Case Study 3). The findings illustrate that demand is shaped by routines that extend far beyond the spaces in which water is used, both intentionally and unintentionally, and therefore highlight a distributed web of people and practices that might be involved in demand management. The findings from these empirical enquiries are used to as the basis to work with the water industry to reimagine interventions that engage in the collective context of demand, and elicit conceptual understandings of the processes and actors involved in governing social change. Overall, the approach taken in this thesis demonstrates the vitality of practice-based enquiry that provides deep analytical detail to better understand the mundane yet complex processes that sustain everyday water use. Supplementing the analysis with ideas from a variety of social science disciplines and working alongside the water industry, facilitated by the CASE studentship, pushes the analysis beyond the confines of domestic practices typical of practice-based research. Subsequently this research offers contributions to policy, practice and theoretical developments as it explores the intersections between demand and professional practices and local environments, evaluates interventions, examines practices of demand management, and unravels the possibilities for future intervention. Consequently, though focused on water management in the UK, this research offers insights for other resource agendas and regional contexts, expanding discussions in these spaces to think creatively about avenues for future policy and management practice.

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Van, der Merwe Francois Petrus Johannes. "A method of evaluating an irrigation water use in terms of "efficient, sustainable and beneficial use of water in the public interest"." Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-08282008-110336/.

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19

Munyinda, Kalaluka. "Efficiency of water and nitrogen use by wheat and legumes in Zambia." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75446.

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Maximum wheat (Triticum aestivum L.) yields in Zambia were obtained with weekly irrigation at 85% of class A pan evaporation during the whole irrigation interval and split application of urea N of which the initial portion of the fertilizer was either broadcast and incorporated or broadcast after the crop had established itself. This corresponded with maximum utilization of fertilizer N. The proportion of N derived from fertilizer was independent of fertilizer placement at various water regimes and N utilization was primarily a function of water availability.
Two nonnodulating soybean (Glycine max L.) cultivars, Clark RJ1 and N77, or in their absence Pearl millet (Panicum glaucum L.) were judged to be appropriate reference crops for estimating N$ sb2$ fixation by soybeans using $ sp{15}{ rm N}$ isotope dilution techniques. A local soybean cultivar, Magoye, was rated highest among three cultivars tested for its ability to support N$ sb2$ fixation by Bradyrhizobium japonicum and contributed biologically fixed N$ sb2$ to a subsequent wheat crop.

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Baburai, Nagesh Aravinda Kumar. "The physiological and genetic bases of water-use efficiency in winter wheat." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/11398/.

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Winter wheat (Triticum aestivum L.) is the most extensive arable crop in the UK grown on about 2M ha p.a. There is a need to identify traits to ameliorate yield losses to drought which are on average about 15% per year. These losses will be exacerbated with predicted climate change. The overall objectives of the present study were to investigate the physiological and genetic bases of water-use efficiency (ratio of above-ground dry matter production to evapotranspiration; WUE) in winter wheat grown in UK conditions and to quantify relationships between WUE and yield performance under drought. The present study used a doubled haploid (DH) population of 33 lines derived from a cross between Beaver and Soissons, known from previous work to contrast for WUE. Two glasshouse experiments (2002/3 and 2003/4) and two field experiments (one at ADAS Gleadthorpe, Nottinghamshire in 2002/3 and the other at Sutton Bonington, University of Nottingham in 2004/5) were conducted. In the glasshouse experiments, two irrigation treatments (with and without irrigation) were applied to four genotypes (two parents and two DH lines), and in the field two irrigation treatments (rainfed and fully irrigated) were applied to the two parents and the 33 DH lines. A range of physiological traits was measured, including developmental stages, carbon isotope discrimination (Δ13C), leaf gas-exchange variables, green areas and biomass at sequential samplings, and these traits were related to grain yield. Transpiration efficiency (ratio of above-ground dry matter production to transpiration; TE) was assessed using the established inverse relationship between TE and Δ13c. In the glasshouse, WUE measured as the regression slope of dry matter on water use, did not differ amongst genotypes in 2003, but did in 2004. Soissons showed higher WUE than other genotypes under irrigation, and also higher WUE than Beaver under drought. For measurements of TE according to Δ13. Soissons and line 134G showed lower Δ13C values (higher TE) than line 134E and Beaver (P<0.05) in 2004 under both irrigation and drought. Soissons and line 134G showed consistently higher TE on account of lower stomatal conductance (gs ) and sub-stomatal C02 concentration (C) values. The early developing Soissons and line 134G exhibited greater flag-leaf green area persistence under drought than the late developing Beaver. Beaver tended to use more water than Soissons under both irrigation and drought, but reductions in water use under drought were similar amongst genotypes. Lower seasonal water use for Soissons than Beaver was associated with a smaller root system. There was a tendency for dry matter of Beaver to be more depressed under drought than Soissons in both the years. Overall, it was not possible to detect significant differences in biomass responses to drought amongst the genotypes, but there were consistent genetic differences in WUE and TE observed under both irrigated and droughted conditions. In the field experiments, the onset of drought coincided broadly with anthesis. The average grain yield losses under drought were 0.5 t ha-1 in 2003 and L6 t ha-1 in 2005. Averaging across site/seasons, Δ13C correlated positively with grain yield amongst the 35 genotypes under irrigation (r--0.35; P<0.05) and under drought (r--0.54; P<0.01), indicating a negative trade off between TE and yield. A 13C decreased under drought and a higher TE was associated with a reduction in average flag-leaf gs, measured from flag leaf emergence to anthesis + 4weeks. Stomatal conductance was measured for eight of the 33 DH lines including the parents, and there was a trend for lower Δ13C (higher TE) to be associated with lower gs, The genetic differences in gs, were generally associated with corresponding decreases in Ci and net photosynthetic rate (A). Therefore results suggested that the negative relationship between TE, as indicated by Δ13C and yield was associated with corresponding reductions in seasonal water use. There was a nonsignificant irrigation x genotype interaction at Gleadthorpe in 2003 and Sutton Bonington in 2005 for Δ13C indicating that this trait was of high heritability. There was an irrigation x genotype interaction for grain yield (P<0.05). A small number of genotypes showed higher yield associated with low Δ13C and these outlier lines could potentially be identified for breaking the negative linkage between yield and delta. In summary, WUE was negatively correlated with yield under drought in this population; and season-long water use appeared to be the most important component affecting yield levels under drought. It is suggested that selecting genotypes indirectly for high Δ13C (low WUE) may be a strategy to improve grain yield under drought. In the quantitative genetic analysis, the putative QTLs identified for target physiological traits were generally different at Gleadthorpe in 2003 and Sutton Bonington in 2005. The most confident putative QTLs for Δ13C were mapped on chromosomes 3B (LOD=2.32) and 2D (LOD=1.43). The identification of QTLs as potential candidate genes on these chromosomes may be associated directly with WUE in the Beaver x Soissons DH mapping population. The Δ13C QTL on chromosome 3B was detected commonly in both the irrigation environments and the direction of allelic effects was consistent with the parental differences in Δ13C. This QTL may therefore represent a novel gene for optimising WUE. It is suggested that breeders could optimise TE by selection according to a marker for this gene involving further fine-mapping to identify a marker tightly linked to the gene. Such a marker would also provide a target for gene discovery in future work. The results suggest that water use is the most important component of Passioura's yield model for yield improvement under UK conditions. Nevertheless, WUE and harvest index and their responses under drought will also likely play a role in yield improvement through breeding in the UK targeted at drought-prone environments in future years.

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Mwale, Simon S. "Resource use efficiency of bambara groundnut landraces in response to soil water." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415492.

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22

Williams, Jamie. "The effect of water-use efficiency on catchment runoff in Great Britain." Thesis, Swansea University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678639.

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23

Bousso, Abou Elimane 1952. "Irrigation water use efficiency of crop calorie and protein production in Arizona." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/191991.

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Irrigation water use efficiencies were studied for the State of Arizona in terms of nutritive values such as calories and proteins. The major crops and crop groups, 15 counties, 6 water planning districts, and four irrigation systems were evaluated. Cotton accounted for more than 40 percent of the Statewide total protein production. The most efficient calorie producing crop was potatoe. The feed crops produced the highest percentage of protein. On yield per acre basis, the leading counties were La Paz and Yuma. District IV produced the highest calorie and protein both per acre and acre-foot basis. The overall output/input ratio for the state's irrigated agriculture was found to be 1.79. This ratio was based on 450 feet of pumping lift and considering energy used to deliver and distribute water as the only direct energy input.

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Ottman, Michael J. "Water Use Efficiency of Forage Sorghum Grown with Sub-optimal Irrigation, 2009." College of Agriculture, University of Arizona (Tucson, AZ), 2010. http://hdl.handle.net/10150/203773.

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A forage sorghum irrigation study was conducted at Maricopa, AZ to determine water use and if sub-optimal irrigation increases water use efficiency and profitability. Sorghum was planted on July 10 with a row spacing of 40 inches and irrigated three times with a total of 8.7 inches of water to establish the crop. Variable amounts of irrigation water were applied commencing on Aug 12 based on 25, 50, 75, and 100% of estimated crop water use (evapotranspiration, ET). The plots were 53.3 ft wide (16 rows) and 40 ft long. ET was estimated from soil water measurements using a neutron probe. The total amount of water applied was 15.5, 19.8, 23.7, and 27.8 inches for the 25, 50, 75, and 100% ET treatments, respectively. The forage was harvested on Oct 28 near the soft dough stage. Forage yields adjusted to 70% moisture were 11.3, 16.4, 21.5, and 23.1 tons/acre for the 25, 50, 75, and 100% ET treatments, respectively. Yield produced per inch of water used by the crop (WUEET, water use efficiency of water used in ET) increased with water application. Yield produced per inch of water applied to the crop (WUEirr, water use efficiency of irrigation water applied plus rainfall) also increased with water application, but then decreased from the 75 to 100% ET treatments. Nevertheless, sub-optimal irrigation strategies are not economical using the results from this study assuming a water cost of $45 per acre-foot and a sorghum silage value of $20 per ton. For sub-optimal irrigation strategies to be economical, water costs would have to increase, sorghum silage value would have to decrease, or the differences in the irrigation efficiencies of the strategies being compared would have to be greater than measured in the present study.

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Newby, Adam F. "Increasing Water Application Efficiency in Greenhouse Crop Production UsingGravimetric Data." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366376123.

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26

Gush, Mark Baudert. "Water-use, growth and water-use efficiency of indigenous tree species in a range of forest and woodland systems in South Africa." Doctoral thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10565.

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This study was initiated to explore whether indigenous tree species use less water than introduced plantation tree species, whether they use that water more efficiently in terms of biomass accumulation, and consequently whether there is scope for the expansion of indigenous tree production systems in South Africa.

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Bradley, Richard G. "Modelling the growth and water use of tropical cereals in semi-arid environments." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319604.

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28

Mapeto, Tatenda. "Single tree water use and water-use efficiencies of selected indigenous and introduced forest species in the southern Cape region of South Africa." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/11493.

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In South Africa, the limited extent of indigenous forests accelerated the development of fast-growing introduced species plantations, on which the country is now heavily reliant for its fibre and timber products. However, the plantation forestry industry is challenged with limited freshwater resources, the need for sustainable management of introduced tree species in commercial forest production systems, and a diversity of plant ecological production factors such as soils that have to be manipulated for the purposes of increasing production capacities. Additionally, plantations are established in the limited high rainfall regions of the country and the industry’s water use has been regulated since 1972. Conversely, natural forests also provide valuable goods, however, their slow growth rates have restricted their development as commercial tree production systems. In this regard the forestry industry is continuously seeking to provide for the country’s timber and fibre needs while ensuring the provision of other ecosystem services from tree production systems. Recent developments in the forestry industry have therefore been focused on water use efficiency in current and alternative tree production systems. There is also widespread unsubstantiated belief that indigenous tree species are efficient users of water. Against this background this study sought to explore the single tree water use and water use efficiencies of introduced commercial plantation species (Pinus radiata) and that of important indigenous species (Ilex mitis, Ocotea bullata and Podocarpus latifolius) for timber and fibre production in the southern Cape region of South Africa. Single tree water use measurements were carried out for a year using the heat pulse velocity method. Growth measurements for utilisable stem wood were done on a quarterly basis for the specimen trees and growth increments over the year were determined. Single tree water use efficiency was a calculated as a function of grams of stem wood gained per litre of water transpired. Measurements of daily weather conditions and soil water content were concurrently taken during the year. The relationships between the variables that express daily climatic conditions, soil water content and daily volumes of transpired water were explored. Empirical models for the prediction of daily transpiration as a function of climate and soil water content were then developed using multiple linear regression analysis. Pinus radiata trees exhibited higher totals of volumetric transpiration than the indigenous species. The water use patterns of Pinus radiata showed higher peaks of maximum and minimum daily and seasonal water use while the indigenous species showed temperate patterns of water use throughout the year. Podocarpus latifolius attained the lowest water use efficiency in the year (0.49g/L) while Pinus radiata, Ocotea bullata and Ilex mitis had comparable water use efficiency values ranging between 1g/L to 2.50g/L. Significant positive correlations existed between climatic variables and daily sapflow volumes of the tree specimens. Daily total solar radiation showed the highest positive correlation with daily transpiration and the average value of the correlation coefficient for solar radiation and water use for all tree species was 0.70 (p < 0.001). Empirical models for predicting daily water use integrated the variables expressing plant available moisture and energy. The study enhances our understanding of single tree water use, water use efficiency, the drivers of transpiration and the applicability of such studies in developing rapid estimation techniques for water use in current and alternative South African tree production systems.

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Hughes, Jonathan. "Reducing stomatal density in Hordeum vulgare improves drought tolerance and water use efficiency." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19860/.

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Manipulation of the expression of the epidermal patterning factor (EPF) family of secreted signalling peptides in order to regulate stomatal density has previously been demonstrated to improve water use efficiency in Arabidopsis thaliana (Franks et al., 2015). Following the sequencing of the barley genome an ortholog of EPF2 was identified and overexpressed. HvEPFL1 overexpression limits both entry into, and progression through, the stomatal lineage. Lines overexpressing HvEPFL1 showed significant increases over controls in terms of both water use efficiency and drought tolerance, without a detrimental effect on grain yield. This suggests that the manipulation of stomatal density could be utilised in order to futureproof crops against future climate change.

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Le, Roux Debbie Jeanette. "Growth, water use efficiency and stable carbon isotopes in commercial clones of Eucalyptus." Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/18327.

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The expansion of Eucalyptus plantations to supply timber for an increasing population in South Africa will result in a great reduction in the country's run-off water. If Eucalyptus continues to be the source of timber in South Africa, the selection of more water use efficient species for planting in existing and new areas has to be implemented. An understanding of the physiological factors ruling growth and water use efficiency in Eucalyptus is needed to develop selection criteria for improved water use efficiency and harvestable stem production under a limited water supply. This study investigated the effects of soil moisture availability on the growth and water use efficiency of 6 commercial clones of Eucalyptus commonly grown in South Africa with the aim of determining the following: (i) The extent of clonal variation in growth, dry mass allocation patterns, water use efficiency and the water cost of wood production at 16 months after planting. (ii) The influence of plant physiological traits such as patterns of dry mass allocation, canopy leaf area, leaf canopy density, specific leaf area, foliar nitrogen concentration and instantaneous rates of photosynthesis and transpiration, on growth, water use efficiency and the water cost of wood production. (iii) The complications associated with sampling for stable carbon isotope ratios (δ¹³C) within a eucalypt canopy and the potential use of δ¹³C in plant tissues as a tool for ranking clonal water use efficiencies.

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Nay, Htoon Bhone [Verfasser], and Christiane [Akademischer Betreuer] Werner. "Water use efficiency of rainfed and paddy rice ecosystem : Disentangling agronomic and ecosystem water use of rice / Bhone Nay Htoon. Betreuer: Christiane Werner." Bayreuth : Universität Bayreuth, 2016. http://d-nb.info/1084083981/34.

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Knamiller, C. "The impact of domestic water user cultures on water efficiency interventions in the South East of England : lessons for water demand management." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5329.

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The need for a more sustainable approach to water consumption has increasingly gained attention in the last decade. The domestic sector accounts for over half of abstracted water in the UK and, as such, has become a major target for water efficiency interventions. Current research and water efficiency interventions are dominated by a positivist approach, focusing on a limited range of factors that can be quantitatively measured. This thesis questions the dominant approach and argues that a more holistic overview of water efficiency can be achieved through the consideration of socio-technical and behavioural theories. Taking a more constructivist approach, this research draws on four theories from socio-technical and behavioural fields and combines them to create a framework for the analysis of water efficiency interventions. The framework is applied to two case studies, exploring water users' perceptions of water, water supply, personal water use, and their responses to the water efficiency interventions. The case studies were selected to provide examples of current mainstream approaches to water demand management. Research methods used included semi-structured interviews and observation. The research findings support the argument that the current dominant approach to domestic water efficiency interventions is limited and, in some cases, ineffectual. Issues of trust, knowledge, motivation and the relationships between water users and water companies were raised. The thesis concludes that the use of a constructivist perspective could help to provide a more effective approach to understanding and improving water demand management.

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Pointon, Charlotte. "Essays in the measurement of efficiency for the English and Welsh water and sewerage industry." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/72007/.

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The English and Welsh water and sewerage industry was privatised in 1989 and is characterised by a series of regional monopolies. The majority of consumers currently have no choice in their supplier. The industry is regulated by Ofwat to guarantee the best value for customers whilst enabling the companies to undertake their activities. The motivation of this thesis is to examine the effectiveness of regulation. The aim is to examine five research questions. Firstly, has regulation encouraged convergence amongst the efficiency scores? Secondly, have the 1999 and 2004 price reviews been effective in improving efficiency? Thirdly, is there a capex bias in the industry? The final two aims come from a methodological perspective: firstly, to allow for the incorporation of environmental variables within the measurement of efficiency and secondly, to incorporate the long asset life of capital by incorporating capital as an intertemporal factor of production. Data Envelopment Analysis (DEA) is employed to measure efficiency which is a non-parametric technique that creates a linear frontier over the data. Convergence is examined by drawing from the growth literature to examine -and -convergence. A three-stage DEA model is applied to examine the influence of environmental variables and to obtain an environmental adjusted DEA efficiencey score. Finally, the intertemporal nature of capitala is incorporated through a dynamic DEA model. This thesis reports that whilst regulation has produced limited improvements in the average efficiency, regulation has been effective in encouraging the least efficient firms to catch up with the frontier companies. Ofwat's tightening of the price review in 1999 has produced significant improvements in efficiency, whereas the 2004 price review was relatively lax and had no significant influence. Finally, the thesis highlights that the current regulatory framework induces a preference towards capital expenditure which can have implications on the consumer's bill.

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Acharya, Tej Prasad. "Water Requirements, Use Efficiency, and Insect Infestation in Brussels Sprouts, and Nitrogen Use Efficiency in Sweet Basil under Low Tunnels compared to Open-field Production." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/86610.

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Sustainable vegetable production is one of the most active areas of vegetable research and of concern to all producers. Everyone, both producers and consumers, are concerned with sustainability. Brussels sprouts and sweet basil are high value commodities, but increasing global concerns about water availability, insect-pest problems, and costly fertilizer inputs severely impact the growth and production of these crops. Low tunnels covered with spun-bonded fabric can improve production of vegetables and herbs in Virginia and the U.S. This study investigated the performance of Brussels sprouts and basil grown under low tunnels (LTs), and their relationship with water use efficiency, nitrogen use efficiency, and the level of protection against insect injury. Low tunnels increased yield, number of sprouts, and water use efficiency of Brussels sprout production. In addition, LTs decreased irrigation requirements, irrigation events, leaf feeding injury, and insect populations in comparison to open field. Similarly, LTs increased summer production of sweet basil as measured by fresh weight and biomass. In addition, plant N uptake was greater under the LTs; however, the increase in nitrogen use efficiency was inconsistent.
Master of Science in Life Sciences
Brussels sprouts and sweet basil are economically important cash crops on the East Coast. Brussels sprouts is a Cole crop and an important source of dietary fiber, vitamins (A, C & K), calcium, iron, manganese and antioxidants. Similarly, sweet basil is a member of the mint family and important high-value herb in the U.S. and the world. It is mainly grown for culinary purposes as a dried and fresh spice in the U.S. However, demand for these commodities is increasing. Low tunnels (LTs) covered with spunbonded fabric can be a practical management tool to increase yield. Results from this study indicate that LTs increase yield of Brussels sprouts and basil, water use efficiency and total nitrogen uptake, while reducing insect pest infestation. Therefore, LTs can be a useful tool to improve sustainability of Brussels sprouts and basil production.

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Khosla, Rajiv. "Yield and water use efficiency of different plant populations of dryland corn and sorghum." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06112009-063140/.

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Robertson, Brittany Clare. "Genetic determinants of stomatal density for enhanced water-use efficiency in barley (Hordeum vulgare)." Thesis, Robertson, Brittany Clare (2021) Genetic determinants of stomatal density for enhanced water-use efficiency in barley (Hordeum vulgare). Honours thesis, Murdoch University, 2021. https://researchrepository.murdoch.edu.au/id/eprint/61572/.

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Low stomatal density correlates with robustness to water deprivation and thus holds potential for the improvement of water-use efficiency (WUE) of commercially relevant crops grown in drought-prone environments. Ranking fourth in terms of global agricultural production, barley (Hordeum vulgare L.) is especially amenable to reductions in stomatal density without the caveat of yield impacts. In this study, a collection of 313 diverse barley accessions with global geographic origins was screened revealing varieties with low stomatal densities for use in future breeding programs. Through genome-wide association analysis (GWAS) of the globally derived barley population, 17 quantitative trait loci (QTLs) were identified for the trait of stomatal density for use in molecular marker-assisted breeding strategies. The identification of numerous QTLs confirmed that stomatal density in barley is controlled by multiple genetic loci. QTLs revealed following GWAS analysis were aligned to the reference genome and led to the identification of seven candidate genes for stomatal density in barley. A novel candidate gene encoding a putative subtilisin-like protease was revealed following GWAS analysis, located 63Kb (Kilo base pairs) upstream of a QTL identified on chromosome 4. Functional prediction of the candidate gene was ascertained based on sequence homology with the gene ortholog encoding the subtilisin-like protease SDD1 (STOMATAL DENSITY AND DISTRIBUTION 1), a known negative regulator of stomatal density in Arabidopsis thaliana. A gene-specific molecular marker was designed for the candidate gene encoding a subtilisin- like protease to select for offspring possessing the candidate gene sequence from low stomatal density barley varieties in subsequent breed improvement. The discovery of the novel candidate gene encoding a subtilisin-like protease indicates that conservation of the stomatal development network extends into the barley lineage. The candidate gene encoding a subtilisin-like protease holds potential for the future improvement of WUE in barley.

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Mbave, Zwidofhelangani Aubrey. "Water stress effects on growth, yield and quality of wheat (Triticum aestivum L.)." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/24146.

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Understanding the effects of water stress on wheat growth, yield and quality is essential for good irrigation management. In South Africa most of the wheat production areas are vulnerable to drought stress during crop development. That causes substantial reduction in grain yield, depending on the developmental stage at which water stress occurred. Supplemental irrigation is the main strategy for adaptation and stabilisation of yield under water stress. However, agriculture is the leading single water-use sector locally, consuming about 60% of total available water. Therefore, the need to improve water use efficiency (WUE) in crop production is clear, since South Africa is classified as a water-scarce country. Experiments were conducted under a rain shelter at Hatfield Experimental Farm, University of Pretoria, in the 2010 and 2011 seasons. The main objective of the study was to evaluate the effects of water stress at different stages on growth, yield, and quality of three wheat cultivars, namely Duzi, Steenbras and SST 843. Water stress was imposed by withholding water at either of three growing stages. The first treatment was stressed during tillering stages to flag leaf (stem elongation (SNN)), followed by water stress from flag leaf to the end of flowering (flowering stage (NSN)), and lastly water stress from grain filling to physiological maturing (grain-filling stage (NNS)), whereas optimal supply of water was maintained throughout the season by weekly irrigating to field capacity for the control treatment (NNN). Irrigation treatments and cultivars influenced growth, yield and quality, depending on the developmental stage at which irrigation was withheld. The control treatment (NNN) and the treatment stressed in the flowering stage (NSN) had highest and lowest grain yield respectively in both seasons. Water stressed treatment NSN reduced grain yield by 33% and 35% in the 2010 and 2011 seasons respectively, when compared with the control treatment (NNN). Reduction of grain yield due to stress in the flowering stage (NSN) was ascribed to reduction in the number of seeds per ear, number of ears per unit area, ear length, and flag-leaf photosynthesis rate (Pn). In the flowering stage (NSN) water stress reduced Pn by 59% which was due to increased leaf temperature because of lower transpiration (E) and stomatal conductance (gs). The water stress treatment NSN reduced transpiration by 72% and stomatal conductance by 84% in the flowering stage. Plant height was reduced by 23% because of water stress imposed in the flowering stage (NSN), which consequently decreased biomass yield by 29% in the 2011 season. Growth and yield parameters showed dramatic recovery when stress was terminated during the flag-leaf stage (SNN). The cultivar Steenbras had lower yield reduction under stress, whereas Duzi and SST 843 had higher yield potential under the well-watered conditions (NNN). In the 2011 season SST 843 had higher WUE of 14.2 kg ha-1 mm, which corresponded to higher grain yield of 7210 kg ha-1 and higher ET of 509 mm. Water-stress treatment SNN gave the highest WUE of 14.9 kg ha-1 mm, which corresponded to a total water use (ET) of 451 mm and grain yield of 6738 kg ha-1. Water stress treatments SNN and NNS reduced ET by 27% and 17%, respectively, which translated to 173 mm and 105 mm water saved by each treatment correspondingly. Grain protein content (GPC) was reduced most by the treatment exposed to stress in the stem elongation stage (SNN). However, the GPC was acceptable (>12%) in all treatments in both seasons. Hectolitre mass was reduced most by water stress imposed during grain filling (NNS). Water stress treatment NNS lowered the hectolitre mass by 3% and 4% in the 2010 and 2011 seasons respectively. Generally all quality parameters in the present study were acceptable for all irrigation treatment and cultivars. The hypothesis that water stress in the stem elongation and grain-filling stages will have little effect on yield and improve WUE was accepted. Therefore it can be recommended that supplemental irrigation should be applied from flag leaf to end of flowering (NSN) stages of wheat in order to minimise grain yield losses in the absence of rainfall. Further research should focus on extrapolation of these results to other production regions using crop models.
Dissertation (MInstAgrar)--University of Pretoria, 2013.
Plant Production and Soil Science
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38

Drerup, Philipp [Verfasser]. "Influence of nitrogen and water supply on evapotranspiration, yield and agronomic water use efficiency of winter wheat / Philipp Drerup." Bonn : Universitäts- und Landesbibliothek Bonn, 2017. http://d-nb.info/1132773237/34.

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39

Karlberg, Louise. "Irrigation with saline water using low-cost drip-irrigation systems in sub-Saharan Africa." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209.

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40

Szejner, Paul, and Paul Szejner. "Seasonal Influences on the Carbon-Water Relations in Ponderosa Pine Forests in the Northern Boundary of the North American Monsoon System." Diss., The University of Arizona, 2018. http://hdl.handle.net/10150/626656.

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Climate models have projected that arid and semiarid lands will experience warmer and drier conditions for the next 100 years. For the last twenty years, the Southwestern US has been experiencing one of the worst droughts over the last century, not only threatening ecological systems but also the water security of its population. Understanding the environmental processes that affect arid and semiarid forests are essential to better understand the water and carbon cycles, and tree-ring research has contributed valuable knowledge in this regard. There is a common understanding that moisture-stress has significant impacts on forested ecosystems and thereby on the global carbon and water cycles. Under persistent moisture deficit, a decline in growth, an increased proportion of wildfires, insect outbreaks, and mass-tree-mortality are often observed in arid and semi-arid forests, having large impacts on their carbon budgets and their capacity to act as a carbon sink. This study addresses the seasonal and regional climatic influences on the water-carbon relations in the ponderosa pine forests of the southwestern US (SW). This region is characterized by a complex climatology related to the North American Monsoon system (NAMS). A topic of interest in this dissertation is the role of the summer rainfall after the early-summer hyper-arid period in the region, providing a unique seasonal condition for these ecosystems to thrive. While these forests clearly rely on winter snowpack to drive much of their annual net primary productivity, the temporal and regional extent to which they supplement winter moisture with summer monsoon moisture needs to be clarified. The core of this dissertation is a study of the spatial and temporal variability of the stable carbon and oxygen isotopes in the cellulose of subsections of the tree rings (e.g., earlywood and latewood) collected from a network of thirteen sites along a latitudinal gradient extending from southern Arizona and New Mexico, through southwest Colorado, and up to northern Utah. The analysis is based on biological and physical processes and their close relationships with isotope effects to infer eco-physiological responses to climate variations over the last century. The stable carbon isotopes are used to derive intrinsic Water-Use Efficiency (iWUE) defined by the molar ratio of carbon gain to water loss. The stable oxygen isotope ratio is used to infer the variations on evaporative flux at the leaf level, which depend on stomatal conductance, atmospheric vapour pressure deficit at the leaf surface, and variations in the isotopic ratio of the source water. Both isotopic ratios are used to document variations in tree productivity and hydrologic vulnerability within the context of climate change impacts on this region. During the study, it was found that climate change in the SW has impacted the carbon and water cycles of these forests for at least the past twenty years. Additionally, seasonality influence the eco-physiology of ponderosa pine change along the latitudinal gradient, as shown by significant differences between EW and LW. These differences are explained by the large shifts in seasonal VPD, which are more evident in the southern part of our study region due to the mid-summer arrival of monsoon rains. These findings will be useful for regional natural resource managers and improves our understanding of seasonal influences on forest water–carbon relationships. This approach will also be useful to develop seasonally resolved paleoclimate and paleo-ecophysiological reconstructions to characterize the long-term influence of winter versus summer moisture on carbon-water relations in forested ecosystems.

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Barakoti, Sonia. "Diversity Analysis of Water Systems in the US." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo152545897931429.

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Sabeh, Nadia Christina. "Evaluating and Miniziming Water Use by Greenhouse Evaporative Cooling Systems in a Semi-Arid Climate." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194527.

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Water availability is a common concern in semi-arid regions, such as Southern Arizona, USA. Hydroponic greenhouse crop production greatly reduces irrigation water use, but the study of water use by evaporative cooling has been limited.This project investigated water use by two evaporative cooling systems: pad-and-fan and high-pressure-fog with fan ventilation. All studies were performed in a double-layer polyethylene film-covered greenhouse (28 x 9.8 x 6.3 m) with mature tomato plants (2.9 plants m-2). Water use efficiency (WUE, kg yield per m3 water use) was calculated daily according to ventilation rate, as well as for a 6-month croppipng period, which used temperature-controlled pad-and-fan cooling.Pad-and-fan water use was 3.2, 6.4, 8.5, and 10.3 L m-2 d-1 for ventilation rates of 0.016, 0.034, 0.047, 0.061 m3 m-2 s-1, respectively. High-pressure-fog water use with a single central, overhead line was 7.9, 7.4, and 9.3 L m-2 d-1 for ventilation rates of 0.01, 0.016, 0.034 m3 m-2 s-1, respectively. For pad-and-fan ventilation rates less than 0.034 m3 m-2 s-1, total greenhouse WUE (20 - 33 kg m-3) was similar to field drip irrigation. For the temperature-controlled high-pressure-fog system, total greenhouse WUE (14 - 17 kg m-3) was similar to field sprinkler irrigation.For the 6-month crop cycle, combining water use by closed irrigation and pad-and-fan systems produced a total WUE of 15 kg m-3. Pad-and-fan WUE increased during monsoon conditions due to lower water use rates.Evaporative cooling water use and air temperature were well-predicted by the energy balance model. Predictions of air temperature improved when outside climate the measured conditions at one greenhouse location. Wind tunnel and full-scale studies of natural ventilation demonstrated the value of knowing airflow patterns when designing and operating a high-pressure-fog systemIt is possible for greenhouse tomato production to have a higher WUE than field production, if ventilation rates are not excessive, if closed irrigation is used, and if control methodologies are improved. Water use can be minimized by knowing how the evaporative cooling system affects greenhouse climate and plant responses.

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Harwood, Douglas E. "The Genetic Architecture of Water-Use Efficiency Within and Between Two Natural Populations of Foxtail Pine." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3781.

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The goal of this project was to determine the genetic architecture of water-use efficiency (WUE) for foxtail pine, which included genomic loci, and effect sizes of this trait. Foxtail pine is a subalpine endemic conifer that inhabits two distinct regional populations separated by 500 km in the mountains of California. In order to achieve this goal, a robust linkage map containing thousands of genetic markers was created using four megagametophyte arrays ranging in size from approximately 70 to 95 megagametophytes. Quantitative trait loci (QTL) discovered for WUE were mapped along the linkage map using linear mixed models and five half-sibling families grown in a common garden. Effect sizes of these QTL were tested for differences between the two regional populations of foxtail pine.

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BHATTARAI, SURYA PRASAD, and s. bhattarai@cqu edu au. "THE PHYSIOLOGY OF WATER USE EFFICIENCY OF CROPS SUBJECTED TO SUBSURFACE DRIP IRRIGATION, OXYGATION AND SALINITY IN A HEAVY CLAY SOIL." Central Queensland University. Biological and Environmental Sciences, 2005. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20050903.222650.

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Subedi-Chalise, Kopila. "Impacts of Crop Residue and Cover Crops on Soil Hydrological Properties, Soil Water Storage and Water Use Efficiency of Soybean Crop." Thesis, South Dakota State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10265200.

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Cover crops and crop residue play a multifunctional role in improving soil hydrological properties, soil water storage and water use efficiency (WUE). This study was conducted to better understand the role of crop residue and cover crop on soil properties and soil water dynamics. The study was conducted at the USDA-ARS North Central Agricultural Research Laboratory, located in Brookings, South Dakota. Two residue removal treatments that include low residue removal (LRR) and high residue removal (HRR) were established in 2000 with randomized complete block design under no-till corn (Zea mays L.) and soybean (Glycine max L.) rotation. In 2005, cover crop treatments which include cover crops (CC) and no cover crops (NCC) were integrated into the overall design. Soil samples were collected in 2014, 2015 and 2016. Data from this study showed that LRR treatment resulted in lower bulk density (BD) by 7 and 9% compared to HRR in 2015 and 2016, respectively, for 0-5 cm depth. Similarly, LRR treatment significantly reduced soil penetration resistance (SPR) by 25% in 0-5 cm depth compared with HRR treatment. In addition to this, LRR treatment significantly increased soil organic carbon (SOC) concentrations and total nitrogen (TN) by 22 and 17%, respectively, in 0-5 cm. Similarly, CC treatment resulted in lower BD and SPR by 7% and 23%, respectively, in 0-5 cm depth in 2015 compared with NCC treatment. The LRR significantly increased soil water infiltration by 66 and 22% compared to HRR in 2014 and 2015, respectively. Similarly, the CC treatment significantly increased infiltration by 82 and 22% compared to the NCC in 2014 and 2015, respectively. The significant impact of a crop residue was observed on soil water retention (SWR) in 2014 and 2015 for the 0-5 cm depth. The LRR and CC treatments increased the soil volumetric moisture content (VMC) and soil water storage (SWS) on the surface 0-5 cm depth. However, the trend was not always significant during the growing season. The CC treatment significantly impacted the soybean yield by 14% and WUE by 13% compared with NCC treatment. Some interaction of residue by cover crops was observed on BD, SPR, VMC, and SWS, which showed that the use of cover crops with LRR can be beneficial in improving the soil properties.

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Ma'arup, Rohayu. "The use of genetic diversity from emmer wheat to improve bread wheat." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16634.

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Drought can be defined by Cambridge Dictionary as long period with little or no rain. Australia is the seventh largest wheat producer in the world, but it is the driest inhabited continent from the viewpoint of continental rainfall and streamflow. So, genetic improvement through crossing high-yielding cultivars of bread wheat with cultivated emmer wheats (had gone through early screening), subsequently backcrossing with bread wheat to increase bread wheat characteristics and producing doubled haploid (DH) from BC1F1 is one possible solution for increasing the yield stability of wheat in drought prone areas. The key point of this research study was to evaluate physiological and agronomic traits among the DH lines in optimum conditions for them to fully express their highest potential in 2013. Subsequently, selection was made among the DH lines for two years of trials under irrigated and rainfed conditions (to mimic drought) in 2014-2015 to evaluate genotypes that use water efficiently under drought stress. The relationship of physiology, phenology, and yield components in high water use efficiency genotypes revealed aspects of adaptation in northwestern NSW. The comparisons of bread wheat parents and their respective progenies (DH lines) were explored and diverse responses to soil water stress were observed. Biplot genotype main effect plus genotype by environment interaction (G+GE) of the multi-environment trials (METs) identified ideal genotypes that are stable cultivars across environment. These findings were also strengthened with GWAS analysis that revealed marker trait associations (MTAs) in water deficit conditions were not observed under the irrigated environments. Such lines would allow farmers to maintain income during drought years, as well as increase their income during wet years. The outcomes from this study should be worthwhile to the wheat industries in Australia and India, as some of domesticated bread wheat parents used were commercial cultivars in India.

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Martin-Benito, Dario, Kevin Anchukaitis, Michael Evans, Río Miren del, Hans Beeckman, and Isabel Cañellas. "Effects of Drought on Xylem Anatomy and Water-Use Efficiency of Two Co-Occurring Pine Species." MDPI AG, 2017. http://hdl.handle.net/10150/625999.

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Exploring how drought influences growth, performance, and survival in different species is crucial to understanding the impacts of climate change on forest ecosystems. Here, we investigate the responses of two co-occurring pines (Pinus nigra and Pinus sylvestris) to interannual drought in east-central Spain by dendrochronological and wood anatomical features integrated with isotopic ratios of carbon (delta C-13) and oxygen (delta O-18) in tree rings. Our results showed that drought induces both species to allocate less carbon to build tracheid cell-walls but increases tracheid lumen diameters, particularly in the transition wood between early and latewood, potentially maximizing hydraulic conductivity but reducing resistance to embolism at a critical phase during the growing season. The thicker cell-wall-to-lumen ratio in P. nigra could imply that its xylem may be more resistant to bending stress and drought-induced cavitation than P. sylvestris. In contrast, the higher intrinsic water-use efficiency (iWUE) in P. sylvestris suggests that it relies more on a water-saving strategy. Our results suggest that narrower cell-walls and reduced growth under drought are not necessarily linked to increased iWUE. At our site P. nigra showed a higher growth plasticity, grew faster and was more competitive than P. sylvestris. In the long term, these sustained differences in iWUE and anatomical characters could affect forest species performance and composition, particularly under increased drought stress.

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Awan, Sajjad Zahoor. "Optimization of water use efficiency in tomato (Solanum lycopersicon L.) by transposition of an LeNCED1 transgene." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/49583/.

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The 9-cis-epoxycarotenoid-dioxygenase (NCED) is a key regulatory enzyme in ABA biosynthesis in plants and its overexpression increases ABA levels that can increase water use efficiency (WUE). The use of the „super promoter‟ (sp) to drive an LeNCED1 transgene in tomato greatly improved WUE without affecting long-term plant growth but caused delayed seed germination and reduced rates of seedling establishment. The first aim of the present study was to generate useful, novel variation in NCED transgene expression by allowing an LeNCED1 transgene, driven by a histone H2A promoter (pH2A), to transpose to new positions in the genome. A stabilized activator element linked to a GUS marker gene (sAc) was used to allow transposition of an engineered dissociation element (Ds) containing the LeNCED1 transgene of format Ds1::pH2A::LeNCED1::Ds2 (T-DNA-Ds). In F1 (sAc × Ds) plants transposition was demonstrated by detection of empty donor site through PCR. The F2 generation was screened for stable integration of the Ds element and reduced gs. Three F3 families, namely 59F3, 102F3 and 116F3, were investigated: they showed multiple stable Ds transposition events, had low gs, and a range of growth rates. Genotype 102F5 had wild-type seed germination, higher bulk leaf ABA and xylem sap ABA and 60% higher gravimetric WUE (WUEp). However, 102F5 accumulated 32% less above ground dry weight than wild type under well-watered conditions 56 days after germination. The sAc and Ds approach allowed production of T-DNA-Ds and nptII kanamycin free 102F5 line which retained transposed Ds (Tr-Ds) elements. These progeny were cross pollinated with sAc to reactivate the transposition of the LeNCED1 transgene and should be an excellent material for generating further variation in ABA content. The second aim was to overcome the seed dormancy in high ABA, genotypes such as sp5 and sp12, by testing novel hydroxamic acid NCED inhibitors for their ability to stimulate germination and seedling establishment. Improvement in seed germination in sp12 was observed with two hydroxamic acid compounds, and an increase in seedling growth rate was also observed, although this was not statistically significant.

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Kivalov, Sergey Nikolayevich. "Whole-Canopy Net Ecosystem Exchange and Water Use Efficiency in an Intermittent-Light Environment - Dynamic Approach." Thesis, State University of New York at Albany, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10842781.

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An observed 20-30% increase in forest net ecosystem exchange ( NEE) on partly cloudy days is often attributed to there being more uniform canopy illumination by diffuse radiation when clouds are present. However, the sky on such days is typically populated by fair-weather cumulus clouds, bringing dynamically changing shadow-to-light conditions on the order of minutes to the forest, with radiation alternating from 1000 W m^-2 in the clear sky to less than 400 W m^-2 in under-cloud shadows. These dynamically changing conditions cannot be investigated by the conventional time-averaged eddy-covariance flux method, which requires nearly steady-state turbulent conditions over much longer 20-30-min periods in order for the fluxes to converge to stationary values. We examine the “true” dynamics of the whole-canopy response to the light change by using a practical ensemble-flux method applied to eddy-covariance flux measurements from two distinct forest ecosystems: Harvard Forest (HF, 42.53°N, 72.17°W), temperate mid-latitude forest near Petersham, Massachusetts, USA, and Tapajós National Forest (LBA, 2.86°S, 54.96°W), an Amazonian evergreen tropical forest near Santarem, Pará, Brazil. Using the rapid change in radiative flux that occurs during the transition from cloud-induced shadow to light as a reference starting point, we combine sets of conditional illumination-change shadow-to-light and light-to-shadow transition events characteristic of cumulus-cloud conditions and parametrize distributions of light and shadow durations and rates of light change of the radiative-flux time series for different cloud conditions reported by standard weather stations. We investigate the sensitivity of the dynamics of forest response to the illumination transitions initiated by these conditional events, and identify an unexpected transient NEE maxima when NEE increases above the clear-sky steady-state equilibrium values (NEE_eq) within the first 10 min of the light period after the shadow-to-light transition, that we hypothesize to be a physiological forest response to the abrupt light change due to presence of the intercellular CO₂ pool in the leaf tissues. Overall NEE builds up during the sunlit periods, but in shadow heat and water stresses are reduced, thus increasing the water use efficiency (WUE). To conduct this analysis, we obtain similarity criteria for realizations defined by conditional events to combine them into the ensembles. With 300 similar realizations grab-sampled at 1-s intervals, we can reliably estimate (≤ 5% standard error) dynamic ensemble fluxes resolved on a 5-s time scale. By the successful application of the first-order system of the delay differential equations with the exponential approach-to-equilibrium solutions, we are able to justify the utility of the “Big-Leaf”-model approach to describe whole-canopy fluxes and provide the dynamic parametrizations of the “Big-Leaf” Active Thermal Layer as well as of the Transient Internal Layer above both forests when the light switches on after the cloud pass. By combining results of sensitivity analysis with modelled solutions applied to the real day-long fluctuating-light time series, we show that the variable light during fair-weather clouds (Shadow period duration < 100 s, Light period duration ≥ 300 s) is responsible for an increase in NEE above the NEE_eq of 15-25% for HF and 10-15% for LBA. This indicates that there is a fluctuating-light NEE-enhancement mechanism that can be considered to be a viable alternative to the existing hypothesis of a diffuse-radiation NEE-enhancement mechanism on partly-cloudy days. We show that on such days Diffuse Fraction can be linearly-related to Cloudiness estimated using the shadow-to-light change in a conditional-event radiative-flux ratio, connecting these two NEE-enhancement mechanisms. Combination of increased NEE with the relatively high plateau in WUE allows forests to operate efficiently in partly-cloudy conditions with maxima located in the Cloudiness range [0.1-0.3] and Diffuse-Fraction range [0.35-0.6], suggesting forest adaptations to the preferred lighting conditions and fair-weather cloudiness.

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Schwantes, Ana Paula. "Agricultural resource efficiency and reduction of impacts under land-use and climate change scenarios in Brazil." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/11/11136/tde-02102017-094321/.

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Cerrado is the second largest Brazilian biome and originally corresponded to 24% of the national territory, and since the 1970´s has been under agriculture and cattle activities. Soybean and maize are two of the most important grain-crops found in this region, with an estimated production of approximately 223 millions of tons in the Brazilian 2016/17 harvest. Changes in soil physical properties due to soil management affect productivity. Possible changes in climatic variables may also affect agricultural productivity, either per unit area (land productivity) or per unit of water volume (water productivity). One option for studying the relation between land and water productivity and how they are affected by soil hydraulic properties and climatic factors is by using an agro-hydrological model. In this study, the aim was to quantify aspects of the soil water balance and to make estimates of land and water productivity for soybean in a clay soil and maize in a medium texture in the Cerrado region using SWAP simulations for different irrigation strategies. Effects on agricultural productivity of a climatic prevision with increasing the air temperature and rainfall reduction for the years 2016-2040 were also simulated. Results show that an increase of soil porosity, resulting from a conservation tillage management, leads to a higher infiltration capacity and is shown to increase land and water productivity, when associated to irrigation scenarios. Higher water productivities were observed with only supplementary irrigation. Predicted climate changes will lead to a decrease of approximately 20% by the end of the years 2016-2040 in land productivity, under rainfed conditions.
O Cerrado é o segundo maior bioma brasileiro que originalmente, correspondia a 24% do território nacional, e desde os anos 1970 tem sido utilizado para atividades ligadas à agricultura e pecuária. Soja e milho são duas das mais importantes culturas graníferas encontradas nesta região, com uma estimativa de produtividade de aproximadamente 223 milhoes de toneladas na safra brasileira de 2016/17. Mudanças nas propriedades físicas do solo devido ao manejo do solo afetam a produtividade agrícola. Possíveis mudanças de variáveis climáticas também poderão afetar a produtividade agrícola, tanto por unidade de área (produtividade de terra) ou por unidade de volume de água (produtividade de água). Uma opção para estudar as relações entre a produtividade de água e de terra e como elas são afetadas pelas propriedades hidraulicas do solo e pelos fatores climáticos é pela utilização de um modelo agro-hidrológico. Neste trabalho, o objetivo foi quantificar os aspectos do balanço hídrico do solo e realizar estimativas da produtividade de água e de terra para soja em um solo argiloso e para milho em um solo de textura média, na região do Cerrado, utilizando simulações com o modelo SWAP para diferentes manejos de irrigação. Os efeitos na produtividade agrícola de uma previsão climática com aumento da temperatura do ar e redução da precipitação para os anos 2016-2040 foram também simulados. Os resultados mostram que um aumento na porosidade do solo, resultante de um manejo conservacionista do solo, leva a uma maior infiltração e resulta num aumento na produtividade da terra e da água, quando associado a cenários de irrigação. As maiores produtividades da água foram observadas com irrigação suplementar. As mudanças climáticas previstas levarão a uma diminuição de aproximadamente 20% na produtividade da terra ao final dos anos 2016-2040, em áreas não irrigadas.

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Dissertations / Theses on the topic 'Water use efficiency'

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