Articles de revues : « Crop canopy modification »

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McDonald, Mary Ruth, Bruce D. Gossen, Cezarina Kora, Monica Parker et Greg Boland. « Using crop canopy modification to manage plant diseases ». European Journal of Plant Pathology 135, n^o 3 (17 janvier 2013) : 581–93. http://dx.doi.org/10.1007/s10658-012-0133-z.

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Sandhu, Sarabjot Kaur, et L. K. Dhaliwal. « Role of agronomic manipulations in modification of wheat microclimate under central Punjab ». Journal of Applied and Natural Science 8, n^o 4 (1 décembre 2016) : 1905–11. http://dx.doi.org/10.31018/jans.v8i4.1060.

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Wheat crop is influenced by different microclimatic parameters like solar radiation, canopy temperature etc. Agronomic manipulation like change in row spacing and row direction can be used as a strategy to modify the microclimate of crop. Keeping these facts in view, field trials were conducted during rabi 2012-13 and 2013-14 under two experiments in first experiment wheat varieties HD 2967, PBW 550 and PBW 343 were sown under three row spacing viz. 15 cm, 22.5 cm and 30 cm. In second experiment, wheat varieties HD 2967, PBW 550 and PBW 343 were sown under two row direction viz. North-South (N-S) and East-West (E-W). Short wave radiation interception and canopy temperature was recorded under different treatments at 15 days interval. Among different row spacing, short wave radiation interception and canopy temperature was maximum at 30 cm row spacing (77.7% and 25.1oC) followed by 22.5 cm (75.7% and 24.2oC) and 15 cm row spacing (73.9% and 23.2oC), whereas under row directions short wave radiation interception and canopy temperature was more (76.5% and 23.9oC) in E-W row direction as compared to N-S row direction (75% and 23.2oC). Relationships were developed between dry matter accumulation and canopy temperature. Polynomial relationships gave significant R2 value (0.66 & 0.69) under different treatments. This two year study indicated that agronomic manipulations play an important role in microclimate modification and canopy temperature significantly influence dry matter accumulation under different crop geometry.

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Thakur, P., et Sonam Singh. « Impact of tree management on growth and production behaviour of intercrops under rainfed agroforestry ». Indian Journal of Forestry 31, n^o 1 (1 mars 2008) : 37–46. http://dx.doi.org/10.54207/bsmps1000-2008-5213m3.

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This investigation was aimed to evaluate the impact of changes in incident radiation through crown modification on crop performance. Different shade intensities created through tree crown management significantly affected growth, physiological attributes and yield related parameters in Vigna mungo (syn. Phaseolus mungo) and Pisum sativum grown as understorey field crops with Morus alba under rainfed conditions. The crown management treatments namely, no crown removal, 25, 50 and 75% crown removal resulted in 91, 85, 63 and 47% shade, respectively. Plant height, number of flowers, leaf area of crops was reduced significantly with the increase in shade intensities and decrease in distance from the tree trunk. Higher pods per plant, grains per pod, grain yield and harvest index were observed at lower shade intensities. Growth and yield were maximum in open control (without tree); while unmanaged canopy of Morus trees caused overall yield reduction of 42% beneath canopy up to 3 m distance from the tree trunk. The crown management regulated physiological attributes in the field crops. The maximum photosynthetic rate was recorded for open plot plants, which declined in plants beneath dense canopy. The amount of water transpired from the crop plants decreased with increase in shade intensity. The conversion efficiency was maximum for plants growing as sole crop which decreased with increasing shade intensities. Based on the results of present investigation, it can be recommended that out of the four tree canopy management options tried i.e. 0, 25, 50 and 75% crown removal; 75% crown removal causing least negative effects on crop growth and yield may be adopted as a compromised crown management practice.

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Jambhulkar, Prashant P., M. L. Meghwal et G. S. Ameta. « Microclimatic Modification of Tomato Crop Canopy to Alter Conidial Dispersal ofAlternaria solani ». Vegetos- An International Journal of Plant Research 28, n^o 4 (2015) : 155. http://dx.doi.org/10.5958/2229-4473.2015.00098.1.

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Bravetti, B., V. Lanari, E. Manni et O. Silvestroni. « CANOPY DENSITY MODIFICATION AND CROP CONTROL STRATEGIES ON 'MONTEPULCIANO' (VITIS VINIFERA L.) ». Acta Horticulturae, n^o 931 (mars 2012) : 331–37. http://dx.doi.org/10.17660/actahortic.2012.931.37.

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Yang, Yubin, Livia Paleari, Lloyd T. Wilson, Roberto Confalonieri, Adriano Z. Astaldi, Mirko Buratti, Zongbu Yan, Eric Christensen, Jing Wang et Stanley Omar P. B. Samonte. « Characterizing Genotype-Specific Rice Architectural Traits Using Smart Mobile App and Data Modeling ». Agronomy 11, n^o 12 (28 novembre 2021) : 2428. http://dx.doi.org/10.3390/agronomy11122428.

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The quantity and quality of light captured by a plant’s canopy control many of its growth and development processes. However, light quality-related processes are not very well represented in most traditional and functional–structural crop models, which has been a major barrier to furthering crop model improvement and to better capturing the genetic control and environment modification of plant growth and development. A main challenge is the difficulty in obtaining dynamic data on plant canopy architectural characteristics. Current approaches on the measurement of 3D traits often relies on technologies that are either costly, excessively complicated, or impractical for field use. This study presents a methodology to estimate plant 3D traits using smart mobile app and data modeling. Leaf architecture data on 16 genotypes of rice were collected during two crop seasons using the smart-app PocketPlant3D. Quadratic Bézier curves were fitted to leaf lamina for estimation of insertion angle, elevation angle, and curve height. Leaf azimuth angle distribution, leaf phyllotaxis, canopy leaf angle distribution, and light extinction coefficients were also analyzed. The results could be used for breeding line selection or for parameterizing or evaluating rice 3D architectural models. The methodology opens new opportunities for strengthening the integration of plant 3D architectural traits in crop modeling, better capturing the genetic control and environment modification of plant growth and development, and for improving ideotype-based plant breeding.

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Nur Arina, I., M. Y. Martini, S. Surdiana, R. Mohd Fauzi et S. Zulkefly. « Radiation Dynamics on Crop Productivity in Different Cropping Systems ». International Journal of Agronomy 2021 (13 mars 2021) : 1–8. http://dx.doi.org/10.1155/2021/4570616.

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Global demand for food has always been on the increase due to the increase of the population in this world. Intercropping is one of the alternatives of agronomic practices that is widely practiced in ensuring food security and enhancing yield stability. Strip, mixed, and relay intercropping can be practiced to increase crop production. In addition to achieving a successful intercropping system, factors such as suitable crops, time of sowing, maturity of the crop, and plant density need to be considered before and during planting. Besides, practiced intercropping becomes a useful cropping system to increase efficient resource utilization, enhance biodiversity, promote soil health, enhance soil fertility, erosion control, yield advantage, weed, pest, and disease control, insurance against crop failure, ecosystem and modification of microclimate, market instability, and increase farmers income. Crop productivity in any types of cropping system implemented relies primarily on the interception of photosynthetically active radiation (PAR) of crop canopy and conversion of intercepted radiation into biomass or known as radiation use efficiency (RUE). Both PAR and RUE are important measurements that have significant roles in crop growth and development in which the accessibility of these radiation dynamics is connected with the leaf area index and crop canopy characteristics in maximizing yield as well as total productivity of the crop component in intercropping systems.

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Hlaváčiková, Hana, et Viliam Novák. « Comparison of daily potential evapotranspiration calculated by two procedures based on Penman-Monteith type equation ». Journal of Hydrology and Hydromechanics 61, n^o 2 (1 juin 2013) : 173–76. http://dx.doi.org/10.2478/johh-2013-0022.

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Abstract Paper presents comparison of the daily reference crop (grass vegetation cover) potential evapotranspiration results calculated by the two modifications of the Penman-Monteith type equation. The first modification was published in FAO recommendation (Allen at al., 1998), PM-FAO, the second is modification according to Budagovskiy (1964) and Novák (1995), PM-BN. Both are used in soil water simulation models HYDRUS-1D and GLOBAL. Calculations were performed for frost-free seasons of the years 2000-2009, using the meteorological station Gabčíkovo (South Slovakia) meteorological data and canopy characteristics. The results indicate significant differences in daily and seasonal potential evapotranspiration. Reasons for those differences are discussed; they should be in different net radiation and aerodynamic resistance estimation methods.

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Jiménez-Pérez, Alfredo, Manuel J. Cach-Pérez, Mirna Valdez-Hernández et Edilia De la Rosa-Manzano. « Effect of canopy management in the water status of cacao (Theobroma cacao) and the microclimate within the crop area ». Botanical Sciences 97, n^o 4 (19 décembre 2019) : 701–10. http://dx.doi.org/10.17129/botsci.2256.

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Background: Cacao is an umbrophile species and therefore the handling of shade by producers can cause a microclimatic modification that influences the physiology of the plant. Questions: Can canopy management influence the microclimate of the crop area and the water content of cacao? Species of study: Theobroma cacao L. (Malvaceae). Study site: Comalcalco, Tabasco, Mexico; dry and rainy season 2018. Methods: Three sites were selected with an open canopy (OC) and three with a closed canopy (CC), where we determined air temperature and humidity, soil temperature, vapor pressure deficit, photosynthetically active radiation, soil water potential and leaf water potential in 15 cacao trees and the sap flow density in 12 trees, by canopy condition and by season. Results: Higher values of solar radiation, air and soil temperature, vapor pressure deficit and lower relative humidity were recorded under OC compared to CC, in both seasons. Differences in soil water potential between 10 and 60 cm depth in CC were recorded during the dry season. There was a lower sap flow density and daily water use in OC. The leaf water potential was similar between canopy conditions, in both seasons. Conclusions: Changes in canopy coverage significantly modify the microclimate of the crop area, a less stressful environment being generated under closed canopy conditions, influencing the sap flow density of cacao trees.

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FAYAZ AHMED BAHAR et K.N. SINGH. « Modification of crop ecology in maize (Zea mays) through fertility levels and weed control measures under temperate conditions of Kashmir ». Indian Journal of Agronomy 58, n^o 3 (10 octobre 2001) : 349–53. http://dx.doi.org/10.59797/ija.v58i3.4198.

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A field experiment was conducted during kharif seasons of 2008 and 2009 at Sher-e-Kashmir University of Ag- ricultural Sciences and Technology Kashmir to study the effect of fertility levels, mulching and weed management practices on the microclimate of crop, soil temperature, phenological changes and yield of maize (Zea mays L.). The experiment was conducted in a split-plot design with three replications and consisted of four treatments viz; N , N + Azotobacter, N , and N + Azotobacter in main plots and five treatments viz; polyethylene mulch, 90 90 120 120 straw mulch @ 1.0 tonne/ha, hand weeding at 30 and 60 DAS, atrazine @1.0 kg a.i./ha and weedy check in sub- plots. Results revealed that N + Azotobacter produced grain yields at par with N , resulting in saving of 30 kg N/ 90 120 ha. Highest grain yield 5.14 t/ha, stover and biological yield with concomitant increase in yield attributes viz; num- ber of cobs/plant, number of rows/cob, number of grains/row, cob length, cob diameter, 1,000-grains weight was obtained with polyethylene mulch. Polyethylene mulch also helped plants to reach phenological stages two to four days earlier as compared to unweeded check. Percentage of light interception by crop at the middle of the canopy was maximum with N + Azotobacter, more than other fertility levels. However, N treatment recorded the high- 120 90 est percentage of light interception among all the fertility levels, when recorded at the bottom of the canopy. Light interception was most with polyethylene mulch among all the weed control treatments when recorded at the middle of the canopy, whereas it was most with weedy check treatment when recorded at the bottom of the canopy. The peak values for the interception of radiation were observed at 90 DAS. The soil temperature in the polyethylene mulched plots was 680C higher as compared to un-mulched plots. Modification of crop ecology through polyethylene mulch and straw mulch resulted in 73.4% and 72.6% more grain yield, respectively, as com- pared to uncontrolled weedy check. Benefit cost ratio was the highest with N + Azotobacter and atrazine @ 1.0 120 kg/ha, respectively.

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Chen, Huanxuan, Xinxin Zhao, Yingchun Han, Fangfang Xing, Lu Feng, Zhanbiao Wang, Guoping Wang et al. « Competition for Light Interception in Cotton Populations of Different Densities ». Agronomy 11, n^o 1 (18 janvier 2021) : 176. http://dx.doi.org/10.3390/agronomy11010176.

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Modification of the cotton canopy results in shade avoidance and competition for light, which shows that density and spatial arrangement of cotton have a great impact on light interception. This experiment was conducted in 2018 and 2019 in the experimental field at the Institute of Cotton Research of Chinese Academy of Agricultural Science in Anyang city, Henan Province, China. Six plant densities of cotton variety SCRC28 were used to assess spatial competition for light in cotton populations during the whole growing period. Light interception data were collected and analyzed according to the spatial grid method and the extension of Simpson’s 3/8 rule. The results showed that at the bottom of the canopy, greater light interception was observed at high densities than at low densities, while in the external part of the layer of the canopy in the horizontal direction, low light interception was recorded at low densities. Leaf area, aboveground biomass and plant height were obviously correlated with light interception, and the cotton population with a higher density (8.7 plants m−2) performed best at the light interception competition, and with the highest yield. The results will provide guidance on light management through the optimization of the structure of the canopy to provide more solar radiation and a significant basis by which to improve the management of light and canopy architecture.

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Johnson, IR, AJ Parsons et MM Ludlow. « Modelling Photosynthesis in Monocultures and Mixtures ». Functional Plant Biology 16, n^o 6 (1989) : 501. http://dx.doi.org/10.1071/pp9890501.

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A comparison is made between two models of canopy photosynthesis for monocultures that differ in their treatment of the variation of the rate of single-leaf photosynthesis in response to the irradiance in which the leaves have grown. Both are shown to be deficient, and a simple modification to one that results in a much improved performance is presented. The theory uses the non-rectangular hyperbola for the rate of single-leaf photosynthesis and incorporates the Monsi-Saeki approach for the light-intercepting characteristics of the canopy. The model is then extended to describe the photosynthesis of mixed canopies, which requires knowledge of the relative position of each leaf-area component within the sward. Analytical expressions can be derived for the case where the leaf-area components are homogeneously distributed relative to each other through the depth of the canopy. This is shown to be a good representation of leaf-area distributions in continuously grazed temperate grass-clover swards as well as frequently cut tropical grass-legume swards, and so is an important special case.

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Robertson, Michael J., Graham D. Bonnett, R. Michael Hughes, Russell C. Muchow et James A. Campbell. « Temperature and leaf area expansion of sugarcane : integration of controlled-environment, field and model studies ». Functional Plant Biology 25, n^o 7 (1998) : 819. http://dx.doi.org/10.1071/pp98042.

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Canopy development is an important determinant of crop radiation interception, and in the absence of stress is mainly driven by temperature. The responses to temperature of the component processes of canopy dynamics in sugarcane: leaf appearance, leaf size, tillering, and leaf senescence, were analysed for the commercial Australian cultivar, Q117. Data were derived under optimal growth conditions from controlled environments, and from irrigated field studies in subtropical and tropical locations. Regression of number of fully-expanded leaves in field-grown plants against cumulative thermal time revealed that the thermal time between the appearance of successive leaves increased as a function of leaf number, such that leaf 1 required 86˚Cd and leaf 40 required 160˚Cd. At any moment, on average there were 3.7 leaves still expanding on the stalks. Functions describing leaf appearance gave acceptable prediction of the time course of leaf appearance taken from independent datasets of field-grown plant and ratoon crops. Leaf size increased with leaf position, with the largest leaves observed at approximately leaf 17 and above. Combining functions describing leaf appearance and leaf size as a function of leaf position allowed estimation of leaf area index (LAI) of main stems in plant and ratoon crops in subtropical and tropical environments. Tiller LAI, derived by difference, accounted for 60–90% of total LAI at the 5- leaf stage, declining to 20–50% at the 15-leaf stage. Plant and ratoon crops were similar in terms of the amount and proportion of tiller LAI. Combining data from all field studies indicated under potential growth conditions, leaf senescence was closely related to leaf production. The functions derived in this study give a basis for simulating canopy dynamics under potential growth conditions in sugarcane, though the extent of genotypic variation for the key parameters and their modification by stress remains to be assessed.

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Zhou, Zhenxiang, Paul C. Struik, Junfei Gu, Peter E. L. van der Putten, Zhiqin Wang, Xinyou Yin et Jianchang Yang. « Leaf-colour modification affects canopy photosynthesis, dry-matter accumulation and yield traits in rice ». Field Crops Research 290 (janvier 2023) : 108746. http://dx.doi.org/10.1016/j.fcr.2022.108746.

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Sangjan, Worasit, et Sindhuja Sankaran. « Phenotyping Architecture Traits of Tree Species Using Remote Sensing Techniques ». Transactions of the ASABE 64, n^o 5 (2021) : 1611–24. http://dx.doi.org/10.13031/trans.14419.

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HighlightsTree canopy architecture traits are associated with its productivity and management.Understanding these traits is important for both precision agriculture and phenomics applications.Remote sensing platforms (satellite, UAV, etc.) and multiple approaches (SfM, LiDAR) have been used to assess these traits.3D reconstruction of tree canopies allows the measurement of tree height, crown area, and canopy volume.Abstract. Tree canopy architecture is associated with light use efficiency and thus productivity. Given the modern training systems in orchard tree fruit systems, modification of tree architecture is becoming important for easier management of crops (e.g., pruning, thinning, chemical application, harvesting, etc.) while maintaining fruit quality and quantity. Similarly, in forest environments, architecture can influence the competitiveness and balance between tree species in the ecosystem. This article reviews the literature related to sensing approaches used for assessing architecture traits and the factors that influence such evaluation processes. Digital imagery integrated with structure from motion analysis and both terrestrial and aerial light detection and ranging (LiDAR) systems have been commonly used. In addition, satellite imagery and other techniques have been explored. Some of the major findings and some critical considerations for such measurement methods are summarized here. Keywords: Canopy volume, LiDAR system, Structure from motion, Tree height, UAV.

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Sudmeyer, R. A., M. C. Crawford, H. Meinke, P. L. Poulton et M. J. Robertson. « Effect of artificial wind shelters on the growth and yield of rainfed crops ». Australian Journal of Experimental Agriculture 42, n^o 6 (2002) : 841. http://dx.doi.org/10.1071/ea02018.

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There is great interest in quantifying and understanding how shelter modifies crop growth and development under Australian conditions. Small constructed enclosures (shelters) can consistently reduce wind speed, allowing experiments to be run with replicated sheltered and unsheltered treatments in close proximity. The aim of this study was to quantify the effect on microclimate of consistently reducing wind speed by 70% and explain the consequences for dryland wheat (Triticum aestivum), lupin (Lupinus angustifolius) and mungbean (Vigna radiata) growth and development, at sites in Queensland, Victoria and Western Australia. Crops were grown inside and outside of artificial shelters, 10 by 10 m and extending 1 m above the crop canopy throughout the growing season. Mean daily air and soil temperatures and atmospheric vapour pressure inside the shelters were largely similar to unsheltered conditions. However, clear diurnal trends were evident; daily maximum temperature and vapour pressure deficit (VPD) were increased in shelter when crops were establishing or senescing. When leaf area index (LAI) was reduced in the shelters, soil temperature was greater than in the open, however when LAI was increased in the shelters, soil temperature was less than in the open. Grain yield in shelters ranged between 78 and 120% of unsheltered yield, depending on seasonal conditions and crop species; the mean yield for all sites, crops and years was 99% of unsheltered yield. In the absence of waterlogging, sheltered crops tended to develop more leaf area than unsheltered crops, with an increase in the ratio of leaf area to above-ground biomass. This greater leaf area did not increase soil water use. While LAI was increased by shelter, only 2 of the 6 sheltered crops that were not waterlogged yielded significantly more grain than the unsheltered crops. This may be because the sheltered crops experienced greater maximum temperatures and VPD during anthesis and grain filling than unsheltered crops. Also, net photosynthesis may not have increased in the shelters after canopy closure (LAI>3–4). Lupins, which developed more leaf area inside shelters, may have experienced strong competition for assimilates between developing branches, flowers and fruit. When rainfall was above average and the soil became waterlogged for part of the growing season, grain yield was reduced inside the shelters. Reduced evaporation inside the shelters may have extended the duration and severity of waterlogging and increased stresses on sheltered plants when potential yield was being set. The reductions in wind speed achieved inside the artificial shelters were greater than those likely in conventional tree windbreak systems. Analysis of crop growth illustrated that microclimate modification at this high level of shelter can be both beneficial and harmful, depending on the crop species and climatic conditions during the growing season.

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Huarte, H. R., et R. L. Benech Arnold. « Understanding mechanisms of reduced annual weed emergence in alfalfa ». Weed Science 51, n^o 6 (décembre 2003) : 876–85. http://dx.doi.org/10.1614/p2002-140.

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Field experiments were carried out at the Facultad de Agronomía, Universidad de Buenos Aires, Argentina (34°25′S, 58°25′W), to evaluate the possibility of reducing weed seedling emergence through the use of alfalfa cultivars with low levels of winter dormancy and by increasing plant density from 200 to 400 plants m−2. It was hypothesized that these treatments would alter the temperature regime and the red (R)–far-red (FR) ratio of radiation to which seeds were exposed. Responses to management treatments were recorded for bull thistle, cotton thistle, plumeless thistle, tall rocket, mustard, curly dock, and pigweed. During the alfalfa establishment year, pigweed and curly dock emergence was reduced by the nondormant cultivar established at high density. This reduction disappeared when soil beneath the canopy was fitted with heaters that mimicked bare-soil temperatures. Crop canopy presence during the establishment year was not effective in reducing mustard, cotton thistle, bull thistle, plumeless thistle, and tall rocket emergence. During the second and third years after crop establishment, the canopy of the nondormant alfalfa cultivar was effective in reducing germination of weed seeds placed on the soil surface during fall and winter. In contrast, the winter-dormant cultivar allowed the establishment of weeds during the winter period. These reductions in weed emergence were associated with a modification in the R–FR ratio perceived by the seeds located at the soil surface and could largely be removed by using FR filters to increase the R–FR ratio. These results suggest that the selection of a nondormant cultivar combined with an increase in plant density could effectively reduce weed populations in alfalfa.

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Somkuwar, R. G., S. D. Ramteke, S. D. Sawant et Prashant Takawale. « Canopy Modification Influences Growth, Yield, Quality, and Powdery Mildew Incidence in Tas-A-Ganesh Grapevine ». International Journal of Fruit Science 19, n^o 4 (13 décembre 2018) : 437–51. http://dx.doi.org/10.1080/15538362.2018.1555509.

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Bumgarner, Natalie R., Mark A. Bennett, Peter P. Ling, Robert W. Mullen et Matthew D. Kleinhenz. « Canopy Cover and Root-zone Heating Effects on Fall- and Spring-grown Leaf Lettuce Yield in Ohio ». HortTechnology 21, n^o 6 (décembre 2011) : 737–44. http://dx.doi.org/10.21273/horttech.21.6.737.

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Low and high tunnels and root-zone heating systems are proven tools in horticultural production. However, impacts of their separate and combined application on crop yield, composition, and microclimates are underreported. We addressed these gaps in the literature by exposing lettuce (Lactuca sativa) to four microclimates established with low and high tunnels and root-zone heating during the spring and fall of 2 years in Wooster, OH. Red-leaved romaine lettuce cultivars Outredgeous and Flagship were direct-seeded into raised beds in both outdoor and high-tunnel settings in early October and late March and harvested multiple times over 4 weeks. Half of all plots in each setting were underlain by electric heating cables, and half were covered with 0.8-mil, clear, vented, low tunnels. A growing medium consisting of peat moss, compost, soil, and red clover (Trifolium pratense) hay was used, and all plots were overhead-irrigated. Soil and air temperatures were monitored throughout the experiments, which were repeated four times (2 seasons/year × 2 years). Here, we report primarily on treatment effects on crop yield and related variables. Root- and shoot-zone conditions and cultivar significantly affected leaf biomass in both settings (outdoor, high tunnel), while population was more often affected in the outdoor experiments. Microclimate main effects were more prevalent than cultivar effects or interactions. Leaf yield was greater in low-tunnel-covered and bottom-heated plots than in uncovered and unheated plots. We take these data as further evidence of the potential to alter lettuce yield through root- and shoot-zone microclimate modification, particularly in regions prone to dynamic seasonal and within-season temperature and light conditions. The data also suggest that the relative performance of low and high tunnels in the production of short-statured, quick-cycling crops during fall and spring be more thoroughly evaluated.

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Tan, CS, WS Meyer, RCG Smith et HD Barrs. « Alternative methods of estimating water deficit stress of wheat grown on undisturbed and repacked soil in drainage lysimeters ». Australian Journal of Agricultural Research 41, n^o 2 (1990) : 267. http://dx.doi.org/10.1071/ar9900267.

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The effect of soil modification on changing the availability of water and the onset of crop water deficit stress in wheat was assessed during 2 drying periods. The different methods of determining the onset of stress generally agreed with each other. Differences were either related to the different parts of the canopy measured or to different physiological processes measured. Because foliage temp. was continuously monitored, the dynamic development of stress in relation to increasing soil water deficit and root growth became evident. The allowable soil water deficit at the onset of stress varied widely between soil treatments and the stage of crop growth at which deficit stress occurred. Physically modifying the soil increased plant available water by 80%. This resulted from both changes in amount of soil water stored and through a more uniformly distributed root system. Wheat growing in undisturbed soil was unable to adapt to post-anthesis stress, as frequent irrigations prior to anthesis concentrated root distribution in the upper layers.

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Gervais, M., P. Bullock, M. Mkhabela, G. Finlay et R. Raddatz. « Improvements to the accuracy of modelled soil water content from the Second Generation Prairie Agrometeorological Model ». Canadian Journal of Soil Science 90, n^o 3 (1 août 2010) : 523–26. http://dx.doi.org/10.4141/cjss09078.

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The direct measurement of soil water on a regional scale is often not practical due to large instrumental and labour requirements. Alternatively, soil water estimates can be derived using models. The Second Generation Prairie Agrometeorological Model (PAMII) models soil water, crop development and evapotranspiration (ET) in order to derive an estimate of crop water use. The objective of this study was to validate, and if necessary modify, the soil water component of PAMII using weather and soil water data collected from several spring wheat trials in Saskatchewan and Manitoba during the 2003 though 2006 growing seasons. Comparison of modelled and measured soil water values yielded a RMSE of 62 mm. For most site-years, PAMII overestimated soil water during the second half of the growing season, which was caused by an increase in modelled canopy resistance (rc) before the crop experienced water stress. The rc function was thus modified so that rc would not increase until the soil water content was < 0.5 of plant available water. Overall this modification reduced the RMSE from 62 to 56 mm. In addition, modelled soil water was underestimated during periods that experienced consecutive days of precipitation. This was because the model stopped infiltration when the top-zone reached saturation. When modified to allow infiltration to continue independent of the top-zone’s water content, the RMSE was further reduced to 53 mm. Overall, both modifications reduced the RMSE of modelled soil water by 9 mm, and this reduction was highly significant (P < 0.01). Key words: Prairie Agrometeorological Model (PAMII), soil water modelling, evapotranspiration, Canadian prairies

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Bubola, Marijan, Sara Rossi, Kálmán Zoltán Váczy, Ádám István Hegyi, Martina Persic, Goran Zdunić, Ena Bestulić, Fumica Orbanić, Zsolt Zsofi et Sanja Radeka. « Modification of Cv. Merlot Berry Composition and Wine Sensory Characteristics by Different Leaf Area to Fruit Ratios ». Applied Sciences 13, n^o 9 (27 avril 2023) : 5465. http://dx.doi.org/10.3390/app13095465.

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This study aimed to evaluate the effects of cluster thinning and severe shoot trimming on berry and wine composition and wine sensory characteristics of Merlot variety, in the context of climate change challenges related to grapevine ripening and the corresponding high alcohol content in wine. In two seasons, two different crop sizes were obtained via cluster thinning and combined in a two-factorial design with severe shoot trimming (SST) and its respective high canopy control (HC). In both seasons, cluster thinning (CT) resulted in higher Brix in grape juice and higher alcohol in wine than full crop size (FC), whereas SST obtained lower values than HC. Total anthocyanins and phenolics in wine were increased by CT, whereas SST had no any significant effect on wine’s phenolic content. Several sensory characteristics of wine were positively affected by CT in both seasons, including aroma intensity, wine body and overall wine quality, whereas SST wines were in one season characterized by increased perception of vegetal aroma, acidity and bitterness, and decreased perception of body, persistency and taste balance. Our results demonstrate that practices which affect the leaf area to fruit ratio have a major impact on wine sensorial characteristics, concluding that their choice should be based on the desired wine style.

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Orzolek, M. D., J. H. Murphy et L. Otjen. « Nonchemical Weed Control in Cabbage ». HortScience 31, n^o 4 (août 1996) : 577c—577. http://dx.doi.org/10.21273/hortsci.31.4.577c.

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Early weed infestation in vegetable crops reduces both early and total marketable yield and quality. Even if escape weeds (12 inches tall or larger) are later killed by a postemergence herbicide application, their skeletons can cause yield loss due to competition for light, temperature modification within the plant canopy, and interference with fungicide and insecticide applications. In addition, weeds can also serve as a reservoir for insect and disease organisms, especially viruses. Experiments in nonchemical weed control in cabbage were conducted at the Horticulture Research Farm, Russell E. Larson Research Center, Rock Springs, Pa., from 1993 to 1995. In addition to weedy and hoed check plots, flaming weeds at 2- to 4-leaf stage of growth with propane gas burners and planting annual ryegrass (Lolium multiflorum) between the rows of cabbage, living mulch, were evaluated during 3 years. The cabbage cultivar Rio Verde was transplanted generally between 15 June and July during each year. Both flaming and living mulch treatments produced yield and head quality similar to the hoed check. Management and timing of ryegrass planting in relation to cabbage establishment is very critical for success with living mulch. Flaming requires straight rows of cabbage or other crop, tractor with driver that can maintain a straight line, and burners that are aligned to burn weeds and not the crop. Results will be discussed.

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Williams, Martin M., Brian J. Schutte et Yim F. So. « Maternal Corn Environment Influences Wild-Proso Millet (Panicum miliaceum) Seed Characteristics ». Weed Science 60, n^o 1 (mars 2012) : 69–74. http://dx.doi.org/10.1614/ws-d-11-00098.1.

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Modification of the cropping environment to make weed seed more susceptible to fatal germination or decay processes is based, in part, on the premise that seed longevity is affected by the crop-influenced environment in which seed is produced, hereafter, called thematernal crop environment. The objective of this investigation was to determine the influence of maternal crop environment on wild-proso millet seed production, germinability, and seed coat tone (i.e., lightness), a trait previously associated with seed longevity in wild-proso millet. Maternal corn environments were established by growing wild-proso millet plants in four morphologically different sweet corn hybrids in four replicates over 2 yr. Wild-proso millet seed was collected at sweet corn harvest, enumerated, characterized for seed coat tone, and tested for germination. Principal component factor analysis reduced six sweet corn traits measured between silking and harvest into a single maternal corn environment factor that accounted for 84% of the variation among crop canopies. Functional relationships between maternal corn environment factor scores and wild-proso millet seed characteristics were clarified by fitting linear models. For each unit decrease in maternal environment factor score, wild-proso millet seed production increased 1,535 seed m−2, germination increased 2.2%, and seed coat tone was 1.8% lighter. These results show the size and germinability of wild-proso millet seed was highest in less-competitive maternal corn environments characterized by a short time to crop maturity and a small crop-canopy size.

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Pinnington, Ewan, Tristan Quaife, Amos Lawless, Karina Williams, Tim Arkebauer et Dave Scoby. « The Land Variational Ensemble Data Assimilation Framework : LAVENDAR v1.0.0 ». Geoscientific Model Development 13, n^o 1 (7 janvier 2020) : 55–69. http://dx.doi.org/10.5194/gmd-13-55-2020.

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Abstract. The Land Variational Ensemble Data Assimilation Framework (LAVENDAR) implements the method of four-dimensional ensemble variational (4D-En-Var) data assimilation (DA) for land surface models. Four-dimensional ensemble variational data assimilation negates the often costly calculation of a model adjoint required by traditional variational techniques (such as 4D-Var) for optimizing parameters or state variables over a time window of observations. In this paper we present the first application of LAVENDAR, implementing the framework with the Joint UK Land Environment Simulator (JULES) land surface model. We show that the system can recover seven parameters controlling crop behaviour in a set of twin experiments. We run the same experiments at the Mead continuous maize FLUXNET site in Nebraska, USA, to show the technique working with real data. We find that the system accurately captures observations of leaf area index, canopy height and gross primary productivity after assimilation and improves posterior estimates of the amount of harvestable material from the maize crop by 74 %. LAVENDAR requires no modification to the model that it is being used with and is hence able to keep up to date with model releases more easily than other DA methods.

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AHMADZADEH, REZA, S. S. SINDHU, K. V. PRASAD, D. K. DAS et R. N. SAHOO. « Mapping and cataloguing of trees of IARI campus, New Delhi, India using GIS and GPS ». Indian Journal of Agricultural Sciences 85, n^o 1 (19 janvier 2015) : 131–36. http://dx.doi.org/10.56093/ijas.v85i1.46073.

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A GIS-based method for locating potential tree-planting sites and modification based on land cover data is introduced. This study introduces a program for developing green spaces in urban areas through (1) land suitability analysis based on GIS; (2) quantifying green areas based on the microclimate suitability; and (3) applying landscapeecology principles in organizing green spaces used to evaluate selected benefits provided by the tree canopy. Arc_GIS environment, a computer program was developed for preparation of different maps such as digitizing, road, building, green space and tree map as well as to classify them. Using GPS the existing trees were physically documented (altitude, latitude, botanical name, common name etc.), the data of which is analyzed using Arc-GIS programme. A comprehensive study of 50 tree species was made out of the large number of genera and various species of approximately 3700 across the IARI Campus. Three different maps of road, building and green were prepared based on the study made.

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Amato, G., L. Stringi et D. Giambalvo. « Productivity and canopy modification of Medicago arborea as affected by defoliation management and genotype in a Mediterranean environment ». Grass and Forage Science 59, n^o 1 (mars 2004) : 20–28. http://dx.doi.org/10.1111/j.1365-2494.2004.00399.x.

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Brun, Laurent, Freddy Combe, Christophe Gros, Pascal Walser et Marc Saudreau. « Protecting Apricot Orchards with Rain Shelters Reduces Twig Blight Damage Caused by Monilinia spp. and Makes It Possible to Reduce Fungicide Use ». Agronomy 13, n^o 5 (10 mai 2023) : 1338. http://dx.doi.org/10.3390/agronomy13051338.

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Blossom and twig blight, caused by Monilinia spp., is the main disease in apricot trees. In this study, we installed transparent rain shelters in apricot orchards to study their influence on the modification of the microclimate at the level of the tree canopy and on the reduction in moniliosis damage in twigs. Rain shelters significantly reduced the leaf wetness time measured within the foliage compared to the unsheltered trees (a reduction of between 43% and 67%). However, very few differences were observed in the daily averaged air temperature (up to 6%) and daily averaged air relative humidity (up to 1%). In the first experiment, on the apricot variety Bergarouge® (CEP Innovation, Lyon, France), moniliosis damage on twigs in the absence of phytosanitary protection was reduced by up to 62% for the trees provided with rain protection compared to the trees that did not receive rain shelters. A second experiment, involving five apricot tree varieties, made it possible to verify that fungicide protection could be reduced for the trees protected by rain covers, reducing moniliosis damage on twigs compared to full fungicide protection combined without rain protection. Finally, a third experiment comprising two apricot tree varieties has shown that in organic orchards, rain protection provides protection against moniliosis (twig blight) that is equivalent to an organic farming fungicide protection programme based on the use of copper sulphate and calcium polysulphide.

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Zheng, Bangyou, Lijuan Shi, Yuntao Ma, Qiyun Deng, Baoguo Li et Yan Guo. « Comparison of architecture among different cultivars of hybrid rice using a spatial light model based on 3-D digitising ». Functional Plant Biology 35, n^o 10 (2008) : 900. http://dx.doi.org/10.1071/fp08060.

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Modification of plant types (i.e. plant architecture) is an important strategy to enhance the yield potential of crops. The aims of this study were to specify rice plant types using 3-D modelling methodology. The architecture of three typical hybrid rice cultivars were measured in situ in a paddy field using a 3-D digitiser at four development stages from the panicle initiation to the filling stage. The structural parameters of the rice canopies were calculated and their light capture and potential carbon gain were simulated based on a 3-D light model. The results confirmed that a plant type with steeper leaf angles let light penetrate more deeply with relatively uniform light distribution in the canopy at higher sun elevation angles, although this result was related to leaf area index. The variations of plant types, however, did not convert into differences of light distribution across rice varieties at lower sun elevation angles. Light use efficiency at the higher leaf area index could be enhanced by reducing mutual-shading. These results indicate that a promising approach to quantify the rice architecture in situ is to combine 3-D digitising and a 3-D light model to evaluate light interception and photosynthesis of rice plant types.

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Freitas, Emanuelle Neiverth de, Robson Carlos Alnoch, Alex Graça Contato, Karoline Maria V. Nogueira, Eduardo José Crevelin, Luiz Alberto Beraldo de Moraes, Roberto Nascimento Silva, Carlos Alberto Martínez et Maria de Lourdes T. M. Polizeli. « Enzymatic Pretreatment with Laccases from Lentinus sajor-caju Induces Structural Modification in Lignin and Enhances the Digestibility of Tropical Forage Grass (Panicum maximum) Grown under Future Climate Conditions ». International Journal of Molecular Sciences 22, n^o 17 (31 août 2021) : 9445. http://dx.doi.org/10.3390/ijms22179445.

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Since laccase acts specifically in lignin, the major contributor to biomass recalcitrance, this biocatalyst represents an important alternative to the pretreatment of lignocellulosic biomass. Therefore, this study investigates the laccase pretreatment and climate change effects on the hydrolytic performance of Panicum maximum. Through a Trop-T-FACE system, P. maximum grew under current (Control (C)) and future climate conditions: elevated temperature (2 °C more than the ambient canopy temperature) combined with elevated atmospheric CO2 concentration(600 μmol mol−1), name as eT+eC. Pretreatment using a laccase-rich crude extract from Lentinus sajor caju was optimized through statistical strategies, resulting in an increase in the sugar yield of P. maximum biomass (up to 57%) comparing to non-treated biomass and enabling hydrolysis at higher solid loading, achieving up to 26 g L−1. These increments are related to lignin removal (up to 46%) and lignin hydrophilization catalyzed by laccase. Results from SEM, CLSM, FTIR, and GC-MS supported the laccase-catalyzed lignin removal. Moreover, laccase mitigates climate effects, and no significant differences in hydrolytic potential were found between C and eT+eC groups. This study shows that crude laccase pretreatment is a potential and sustainable method for biorefinery solutions and helped establish P. maximum as a promising energy crop.

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Chiabrando, V., et G. Giacalone. « Kiwifruit under plastic covering : impact on fruit quality and on orchard microclimate ». Journal of Food, Nutrition and Agriculture 1, n^o 1 (8 mars 2018) : 1. http://dx.doi.org/10.21839/jfna.v1i1.113.

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Italy has a preeminent rank in kiwifruit industry, being the first exporter and the second largest producer after China. However, in the last few years kiwifruit yields and the total cultivated area considerably decreased, due to the disease spread of the bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa). Bacterial canker has affected significantly orchards productivity and consequently has caused severe economic losses in all major areas of kiwifruit cultivation, including Italy,and considerable damage to the international kiwifruit industry.Several climatic conditions and cultural practices affect the development of the bacterial canker.Orchard hygiene, restrictions on the movement of nursery plants, orchard management and cultural practices, chemical and biological controls and breeding programs are being employed to limit the diffusion of the disease and help kiwifruit orchards to survive and produce. A possible way seems to be the modification of environmental conditions and it is being explored through the building of plastic covers over the orchards. This research work is focused on the impact of plastic cover on fruit quality, microclimate conditions and incidence of Psa. To evaluate the impact of plastic cover on microclimate, quality of fruits and disease incidence the following parameters were evaluated: climatic parameters (temperature, PAR), quality parameters (color, fruit firmness, titratable acidity, °Brix, vitamin C), disease incidence (%). The use of a permanenttunnel modify light intensity and microclimate without any negative consequences on kiwifruits quality. Covering a kiwifruit orchard with a protective canopy reduces the spread of Psa throughout the orchard when covers are constructed over vines with low levels of infection.The use of plastic covers ensure the production of the current and future kiwifruit without compromising the quality of the fruit, but future trials will provide further information clarifying the effectiveness of the actual crop covers.

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Mascarini, Libertad, Gabriel A. Lorenzo et Fernando Vilella. « Leaf Area Index, Water Index, and Red : Far Red Ratio Calculated by Spectral Reflectance and its Relation to Plant Architecture and Cut Rose Production ». Journal of the American Society for Horticultural Science 131, n^o 3 (mai 2006) : 313–19. http://dx.doi.org/10.21273/jashs.131.3.313.

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In roses (Rosa ×hybrida L.), the bending of branches is a technique that modifies the canopy of the plant and could affect such parameters as the leaf area index (LAI), the quality of reflected light, and the water index (WI) of the plant. The measurement of spectral reflectance with remote sensors is a nondestructive, quick, and simple method to study these parameters. The aim of this paper is to quantify the modification of reflected radiation quality, the LAI and the water index of the plant with different canopies, and its impact on flowering and the number and quality of flowers produced. In R. ×hybrida `Terracotta', using the spectral crop reflectance, the red: far red ratio [red (R) = 680 nm; far red (FR) = 730 nm], percentage of blue light of reflected radiation, and vegetation indices [normalized difference vegetation index (NDVI), simple ratio index (SRI), water index (WI)] were calculated in two architectural managements: traditional (upright hedge) and bent shoot. NDVI had a greater correlation with LAI than SRI (r2 = 0.98 and 0.85, respectively), but SRI was more reliable for LAI values of 1 to 3.5. The bent shoot system compared to the traditional one decreased the R:FR ratio of reflected radiation and increased LAI and plant water content. These changes were related to a higher commercial quality of the flowers (longer flowering shoots with a larger stem diameter and fresh weight), although there was no significant difference in the number of flowers harvested. The period that showed the largest difference in the quality of the flower using the bent shoot system had a LAI of 2.8 vs. 1.8 with traditional management and a marked reduction in the R:FR of the light reflected by bent plants. The bent shoot system advanced the peak production by 1 month at the end of winter and improved the flowers at a time when sun radiation is limiting factor for production.

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Hodges, Laurie, Entin Daningsih et James R. Brandle. « Comparison of an Antitranspirant Spray, a Polyacrylamide Gel, and Wind Protection on Early Growth of Muskmelon ». HortScience 41, n^o 2 (avril 2006) : 361–66. http://dx.doi.org/10.21273/hortsci.41.2.361.

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Field experiments were conducted over 4 years to evaluate the effects of antitranspirant (Folicote, Aquatrol Inc., Paulsboro, N.J.) and polyacrylamide gel (SuperSorb, Aquatrol Inc., Paulsboro, N.J.) on early growth of transplanted muskmelon grown either protected by tree windbreaks or exposed to seasonal winds. A randomized complete block design (RCBD) with split plot arrangement was used with wind protection (sheltered and exposed) areas as the main treatment and use of an antitranspirant spray or gel dip as subtreatments. Based on destructive harvests in the field, treatments and subtreatments did not affect dry weight or leaf area index in the first 2 years. Specific contrasts, however, showed that gel application significantly increased fresh weight, dry weight, and leaf area index over that of the untreated transplants whereas the spray application tended to reduce these factors during the first 3 weeks after transplanting. Significant differences between gel and spray subtreatments disappeared by 5 weeks after transplanting. Shelterbelts ameliorated crop microclimate thereby enhancing plant growth. Significantly, wind velocity at canopy height was reduced 40% on average and soil temperatures were about 4% warmer in the sheltered plots compared to the exposed plots during the first 5 weeks post-transplant. Muskmelon plants in the sheltered areas grew significantly faster than the plants in the exposed areas in 2 of the 3 years reported, with the 3-year average fresh weight increased by 168% due to wind protection. Overall transplanting success and early growth were enhanced the most by wind protection, followed by the polyacrylamide gel root dip, and least by the antitranspirant foliar spray. We conclude that microclimate modification by wind speed reduction can increase early muskmelon plant growth more consistently than the use of polyacrylamide gel as a root dip at transplanting or the use of an antitranspirant spray. A polyacrylamide gel root dip generally will provide more benefit during early muskmelon growth than the use of an antitranspirant spray.

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Ma, Xu, et Yong Liu. « A Modified Geometrical Optical Model of Row Crops Considering Multiple Scattering Frame ». Remote Sensing 12, n^o 21 (2 novembre 2020) : 3600. http://dx.doi.org/10.3390/rs12213600.

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The canopy reflectance model is the physical basis of remote sensing inversion. In canopy reflectance modeling, the geometric optical (GO) approach is the most commonly used. However, it ignores the description of a multiple-scattering contribution, which causes an underestimation of the reflectance. Although researchers have tried to add a multiple-scattering contribution to the GO approach for forest modeling, different from forests, row crops have unique geometric characteristics. Therefore, the modeling approach originally applied to forests cannot be directly applied to row crops. In this study, we introduced the adding method and mathematical solution of integral radiative transfer equation into row modeling, and on the basis of improving the overlapping relationship of the gap probabilities involved in the single-scattering contribution, we derived multiple-scattering equations suitable for the GO approach. Based on these modifications, we established a row model that can accurately describe the single-scattering and multiple-scattering contributions in row crops. We validated the row model using computer simulations and in situ measurements and found that it can be used to simulate crop canopy reflectance at different growth stages. Moreover, the row model can be successfully used to simulate the distribution of reflectances (RMSEs < 0.0404). During computer validation, the row model also maintained high accuracy (RMSEs < 0.0062). Our results demonstrate that considering multiple scattering in GO-approach-based modeling can successfully address the underestimation of reflectance in the row crops.

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Alagbo, Oyebanji, Michael Spaeth, Marcus Saile, Matthias Schumacher et Roland Gerhards. « Weed Management in Ridge Tillage Systems—A Review ». Agronomy 12, n^o 4 (10 avril 2022) : 910. http://dx.doi.org/10.3390/agronomy12040910.

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Although different modifications of ridge tillage (RT) systems exist in different regions around the world, the positive impacts of RT on crop yields and weed management are quite similar. This review gives a comprehensive summary of different forms of RT and highlights the benefits of RT for crop growth, mainly due to better access to soil moisture, nutrients and light. In temperate areas, RT can accelerate crop emergence because soil temperature is usually higher on the ridge. These stimulating effects increase crop competitiveness against weeds especially in the early period of crop development until canopy closure. RT with crops placed on the top of ridges can also be used for automatically guiding inter-row hoes and intra-row band sprayers. The ridges can replace automatic vision control systems for hoeing and band spraying, which are needed for precise weeding in conventional flat seedbeds. Therefore, RT can be considered a possible platform for smart/robotic weeding. This paper introduces a new RT system using real-time kinematic (RTK) global satellite navigation systems (GNSS) for the ridging and seeding of maize and soybean on top of recompacted ridges. Straight ridges with precise positioning data were used to guide mechanical weeding elements precisely along the crop rows. Simultaneously, weeds in the valleys were suppressed by living mulches. Field experiments with this new technology in maize showed 85.5% weed dry biomass suppression compared to an untreated control and a slightly higher weed control efficacy than mechanical weeding in flat seedbeds.

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Oreja, Fernando H., Diego Batlla et Elba B. de la Fuente. « Effect of soybean crop structure on large crabgrass (Digitaria sanguinalis) growth and seed dormancy ». Weed Science 69, n^o 3 (2 mars 2021) : 372–78. http://dx.doi.org/10.1017/wsc.2021.17.

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AbstractCrop–weed interactions are affected by environmental alterations resulting from a crop’s presence, such as modifications in temperature, light quality and quantity, and moisture conditions that could modify weed performance. The objectives of this work were to study (1) how soybean [Glycine max (L.) Merr.] crop structure modifies the environment under the canopy and large crabgrass [Digitaria sanguinalis (L.) Scop.] plant structure, biomass, and seed production and dormancy; and (2) the relative importance of these environmental changes on the weed’s characteristics. A field experiment in a completely randomized block design with five replicates was performed to evaluate narrow and wide interrow spacing and soybean maturity groups 3 and 4. Measured variables were intercepted solar radiation (RAD); red–far red (R-FR) ratio; humidity; minimum, maximum, and alternating temperatures; and weed biomass, tillers per plant, height, and seed dormancy. Crop canopy reduced solar radiation, R-FR ratio, and daily average maximum and alternating temperatures. Soybean presence reduced the weed biomass, tillers and seeds per plant, and seed dormancy. High solar radiation intercepted by the crop during the reproductive phase was the main environmental variable related to reductions in weed biomass, tillers per plant, and fecundity. The combination of low temperature and solar radiation received by developing seeds was more related to seed dormancy than the rest of the variables. Crop management decisions focused on the fact that keeping the crop canopy alive for a longer time at the end of the season would not only reduce the weed growth but also seed dormancy.

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JOYDEEP MUKHERJEE, BRIJESH YADAV, V.K. SEHGAL, PRAMEELA KRISHNAN et RAJ KUMAR DHAKAR. « Radiation dimming induced modifications in radiation utilization of wheat (Triticumaestivum) crop ». Journal of Agrometeorology 22, n^o 3 (10 novembre 2021) : 332–38. http://dx.doi.org/10.54386/jam.v22i3.294.

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Global dimming has many environmental and climatic implications. India has also experienced a steady and continuous radiation dimming since 1960s due to increasing load of dust and aerosol in the atmosphere. Radiation interception, temperature, humidity and wind profile are altered under reduced light condition which are determining factor for crop phenology, leaf area index, biomass production, grain yield and radiation use efficiency of crops.In this experiment, three wheat cultivars (HD 2967, WR 544 and PBW 502) were grown under five solar radiation treatments i.e. R1 (no shading), R2 (20% shading), R3 (35% shading), R4 (50% shading) and R5 (75% shading) during rabi season of 2014-15 and 2015-16 at research farm of ICAR-Indian Agricultural Research Institute (ICAR-IARI), New Delhi to study the effect of radiation dimming on performance of selected wheat cultivars.In both the years the canopy temperature of wheat from crop vegetative stage to maturity was decreased with increase of shading level. The effect of reduced solar radiation significantly decreased the biomass production and yield.The radiation use efficiency (RUE) for biomass was increased due to shading treatments whereas the RUE for yield decreased with radiation reduction.The RUE for yield was the highest for no shading treatment (0.85 and 0.75 g MJ-1 in 2014-15 and 2015-16, respectively). Among the cultivars, the radiation use efficiency for biomass as well as yield was the highest in HD 2967 followed by WR 544 and PBW 502,respectively.

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ABHISHEK, DHIR, PAL R K, KINGRA P K et MISHRA S K. « Microclimatic conditions and seed cotton yield as affected by sowing time, row orientation and plant spacing under Bt cotton hybrid ». MAUSAM 71, n^o 4 (1 novembre 2021) : 729–38. http://dx.doi.org/10.54302/mausam.v71i4.62.

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Microclimatic modifications are the effective and suitable adaptation strategy to minimize the adverse affect of weather on cotton. In this context, multi-location field experiments were laid out at Bathinda and Faridkot, districts of Punjab during Kharif 2018 with Bt-cotton hybrid RCH 773 BGII and sown at three times i.e., April 30, May 15 and May 30 with two row orientations (North-South: N-S and East-West : E-W) and three plant spacing’s (67.5 cm × 45.0 cm, 67.5 cm × 60.0 cm and 67.5 cm × 75.0 cm) in factorial split plot design and replicated by three times. The results revealed that during the morning (0730 IST) and afternoon time (1430 IST), soil and within-canopy temperature were found higher during emergence and mid growth stages with delayed sowing which reduced the crop growing period and resulted the seed cotton yield to be declined with delayed sowing. On the other hand, morning and afternoon within-canopy relative humidity was recorded higher with delayed sowing during sensitive stages of the crop which provided favorable weather for higher infestation of cotton insect-pest and disease and caused reduction in seed cotton yield at both the study locations. Soil temperature and within-canopy temperature were recorded higher in East-West row oriented, while within-canopy RH was higher under North-South row orientation at both the study regions. During entire growth period of cotton, soil temperature and within-canopy temperature recorded during morning and afternoon hours were found to be increased with increase in plant spacing whereas within-canopy relative humidity during morning and afternoon hours was found to be decreased with increase in plant spacing at both the locations. Among microclimatic parameters, higher variation was observed between sowing dates, while lesser variation was recorded among row orientations and plant spacings.

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Niinemets, Ülo, John D. Tenhunen et Wolfram Beyschlag. « Spatial and age-dependent modifications of photosynthetic capacity in four Mediterranean oak species ». Functional Plant Biology 31, n^o 12 (2004) : 1179. http://dx.doi.org/10.1071/fp04128.

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Drought is one of the most important limitations of photosynthesis in Mediterranean climates. However, Mediterranean sclerophyllous species with long-lived leaves also support extensive and dynamic canopies, with potentially large spatial and age-dependent gradients. We studied within-canopy and temporal patterns in foliage structure, chemistry and photosynthesis in the evergreen species Quercus coccifera L., Q. ilex L. subsp. ballota (Desf.) Samp. in Bol. and Q. suber L. and in the semi-deciduous marcescent species Q. faginea Lam. to determine the role of within-canopy shading and leaf age on foliage functioning. There was a 2.5-fold within-canopy gradient in leaf dry mass per unit area (MA) that was accompanied by a 3-fold range in area-based leaf nitrogen (N) content, the capacity for photosynthetic electron transport (Jmax) and maximum Rubisco carboxylase activity (Vcmax), while the fractional investments of leaf nitrogen in electron transport (FB) and in Rubisco (FR) were relatively constant within the canopy. Leaf aging led to increased MA, larger or constant mass-based N content, larger phosphorous (P) and structural carbon contents, but decreased movable cation contents. Age-dependent increases in MA and N per dry mass meant that Jmax and Vcmax per area were weakly related to leaf age, with a trend of decreasing values in older leaves. However, Jmax and Vcmax per unit dry mass decreased 4-fold across the range of leaf age, primarily owing to decreases in apparent N investments in photosynthetic machinery. This decrease in apparent N investments in photosynthetic machinery was possibly the result of a larger fraction of N bound to cell walls, or of an enhanced CO2 diffusion resistance from the outer surface of cell walls to the chloroplasts in older leaves with thicker and more lignified cell walls. The age-dependent variation in apparent fractional investments of N in photosynthetic machinery reduced the generality of leaf nitrogen v. photosynthesis relationships. Photosynthetic characteristics qualitatively fitted the same patterns with leaf age in all species, but at a common leaf age, area-based leaf photosynthetic potentials depended on species-specific values of MA. These data collectively demonstrate important canopy and age-dependent controls on leaf structure, chemistry and photosynthetic potentials that should be included in larger-scale photosynthesis simulations in Mediterranean climates.

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RIGHI, CIRO ABBUD, VINCENT COUDERC, CARLOS RODRIGUES PEREIRA et HILTON THADEU ZARATE COUTO. « RESPONSES OF EUCALYPTUS CAMALDULENSIS SPROUTS TO SHADE : AN EVALUATION OF CANOPY PLASTICITY ». Experimental Agriculture 52, n^o 3 (16 juin 2015) : 346–58. http://dx.doi.org/10.1017/s0014479715000137.

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SUMMARYEucalyptus spp. is the main tree used in cellulose production worldwide, cultivated mostly in extensive monocrop plantations. However, due to concerns on environmental impacts, fear on decrease of food production related to the size of cultivated area, its location near human settlements with few jobs generation, eucalypt cultivation is no longer encouraged in many places. At the same time, large plantations hold the opportunity to integrate eucalypt into agroforestry systems (AFS) in a variety of production systems with many social, economical and environmental advantages. In this study we studied canopy modifications of E. camaldulensis sprouts under different degrees of shade. The plants were located on a gradient of available solar irradiation ranging from 51 to 94%. E. camaldulensis showed canopy plasticity with modified radiation interception patterns under diverse irradiations. Most of these variations were of small amplitude with some important variables remaining almost unchanged (leaf density, canopy percentage, tree, trunk and canopy height) or increasing only slightly (leaf area index and canopy opening). The main changes presented by E. camaldulensis, with a steep increase towards full sun, were: foliage area, canopy surface, canopy volume and area of canopy projection. In order to design appropriate agroforestry systems with young eucalypt growing under the shade of other crops, it is necessary to determine at which point the observed variable changes can support reasonable production.

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Santos, Antonio Odair, Homero Bergamaschi, Marcel Fuchs, Luís Mauro G. Rosa et João Ito Bergonci. « SUNLIT AND SHADED MAIZE CANOPY WATER LOSS UNDER VARIED WATER STRESS ». Revista Brasileira de Engenharia Agrícola e Ambiental 3, n^o 3 (décembre 1999) : 261–67. http://dx.doi.org/10.1590/1807-1929/agriambi.v3n3p261-267.

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ABSTRACT The precise estimation of transpiration from plant canopies is important for the monitoring of crop water use and management of many agricultural operations related to water use planning. The aim of this study was to estimate transpiration from sunlit and shaded fractions of a maize ( Zea mays L.) canopy, using the Penman-Monteith energy balance equation with modifications introduced by Fuchs et al. (1987) and Fuchs & Cohen (1989). Estimated values were validated by a heat pulse system, which was used to measure stem sap flow and by a weighing lysimeter. A relationship between incident radiation and leaf stomatal conductance for critical levels of leaf water potential was used to estimate transpiration. Results showed that computed transpiration of the shaded canopy ranged from 27 to 45% of the total transpiration when fluctuations in atmospheric demand and the level of water stress were taken in account. Hourly and daily estimates of transpiration showed agreement with lysimeter and heat pulse measurements on the well-watered plots. For the water-limited plots the precision of the estimate decreased due to difficulties in simulating the canopy stomatal conductance.

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Garcia-Vila, Margarita, Rodrigo Morillo-Velarde et Elias Fereres. « Modeling Sugar Beet Responses to Irrigation with AquaCrop for Optimizing Water Allocation ». Water 11, n^o 9 (14 septembre 2019) : 1918. http://dx.doi.org/10.3390/w11091918.

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Process-based crop models such as AquaCrop are useful for a variety of applications but must be accurately calibrated and validated. Sugar beet is an important crop that is grown in regions under water scarcity. The discrepancies and uncertainty in past published calibrations, together with important modifications in the program, deemed it necessary to conduct a study aimed at the calibration of AquaCrop (version 6.1) using the results of a single deficit irrigation experiment. The model was validated with additional data from eight farms differing in location, years, varieties, sowing dates, and irrigation. The overall performance of AquaCrop for simulating canopy cover, biomass, and final yield was accurate (RMSE = 11.39%, 2.10 t ha−1, and 0.85 t ha−1, respectively). Once the model was properly calibrated and validated, a scenario analysis was carried out to assess the crop response in terms of yield and water productivity to different irrigation water allocations in the two main production areas of sugar beet in Spain (spring and autumn sowing). The results highlighted the potential of the model by showing the important impact of irrigation water allocation and sowing time on sugar beet production and its irrigation water productivity.

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Lacasa, Josefina, Ignacio A. Ciampitti, Juan I. Amas, Facundo Curín, Sergio F. Luque et María E. Otegui. « Breeding effects on canopy light attenuation in maize : a retrospective and prospective analysis ». Journal of Experimental Botany 73, n^o 5 (23 décembre 2021) : 1301–11. http://dx.doi.org/10.1093/jxb/erab503.

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Abstract The light attenuation process within a plant canopy defines energy capture and vertical distribution of light and nitrogen (N). The vertical light distribution can be quantitatively described with the extinction coefficient (k), which associates the fraction of intercepted photosynthetically active radiation (fPARi) with the leaf area index (LAI). Lower values of k correspond to upright leaves and homogeneous vertical light distribution, increasing radiation use efficiency (RUE). Yield gains in maize (Zea mays L.) were accompanied by increases in optimum plant density and leaf erectness. Thus, the yield-driven breeding programs and management changes, such as reduced row spacing, selected a more erect leaf habit under different maize production systems (e.g., China and the USA). In this study, data from Argentina revealed that k decreased at a rate of 1.1% year–1 since 1989, regardless of plant density and in agreement with Chinese reports (1.0% year–1 since 1981). A reliable assessment of changes in k over time is critical for predicting (i) modifications in resource use efficiency (e.g. radiation, water, and N), improving estimations derived from crop simulation models; (ii) differences in productivity caused by management practices; and (iii) limitations to further exploit this trait with breeding.

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Guzinski, R., M. C. Anderson, W. P. Kustas, H. Nieto et I. Sandholt. « Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day-night MODIS observations ». Hydrology and Earth System Sciences Discussions 10, n^o 2 (11 février 2013) : 1897–941. http://dx.doi.org/10.5194/hessd-10-1897-2013.

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Abstract. The Dual Temperature Difference (DTD) model, introduced by Norman et al. (2000), uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST) to estimate surface energy fluxes. By using a time differential temperature measurement as input, the approach reduces model sensitivity to errors in absolute temperature retrieval. The original formulation of the DTD required an early morning LST observation (approximately 1 h after sunrise) when surface fluxes are minimal, limiting application to data provided by geostationary satellites at sub-hourly temporal resolution. The DTD model has been applied primarily during the active growth phase of agricultural crops and rangeland vegetation grasses, and has not been rigorously evaluated during senescence or in forested ecosystems. In this paper we present modifications to the DTD model that enable applications using thermal observation from polar orbiting satellites, such as Terra and Aqua, with day and night overpass times over the area of interest. This allows the application of the DTD model in high latitude regions where large viewing angles preclude the use of geostationary satellites, and also exploits the higher spatial resolution provided by polar orbiting satellites. A method for estimating nocturnal surface fluxes and a scheme for estimating the fraction of green vegetation are developed and evaluated. Modification for green vegetation fraction leads to significantly improved estimation of the heat fluxes from the vegetation canopy during senescence and in forests. Land-cover based modifications to the Priestley–Taylor scheme, used to estimate transpiration fluxes, are explored based on prior findings for conifer forests. When the modified DTD model is run with LST measurements acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites, generally satisfactory agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the Danish Hydrological ObsErvatory (HOBE) in western Denmark, indicating realistic patterns based on land use.

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Wien, H. Chris, et David S. de Villiers. « (196) Inducing Lettuce Tipburn with Relative Humidity Modification ». HortScience 40, n^o 4 (juillet 2005) : 1053C—1053. http://dx.doi.org/10.21273/hortsci.40.4.1053c.

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Tipburn is a necrosis of the rapidly expanding young leaves of lettuce, caused by a localized Ca deficiency that is a major constraint to raising productivity of hydroponically-grown leaf lettuce. Root pressure is thought to be important in distributing calcium to young tissue that is not transpiring rapidly in crops such as cabbage, tomato and strawberry. Since root pressure is enhanced by high relative humidity (RH), experiments were conducted with two cultivars of leaf lettuce to determine if regulating relative humidity during the day or night would influence tipburn incidence. Lettuce was grown hydroponically in a glass-covered greenhouse. Plants were transferred to ponds of 1 × 2 m size, starting at about day 25 from sowing. Four ponds containing 42 plants each were subjected to ambient or elevated RH, either during the day, or at night, or at both times. Each pond was covered by a clear polyethylene ventilated canopy, to ensure maintenance of the desired RH condition. The experiment was conducted five times. In three experiments, tipburn developed in 3 or 7 days, depending on the cultivar. The disorder was most severe in ponds whose atmosphere was constantly humid, followed by the treatment that provided humid days and dry nights. Treatments which provided dry conditions, either during the day, or continuously, were least affected. In two experiments, ambient RH rose above 70%, and the differential effect of humidity on tipburn incidence was no longer evident. Both cultivars reacted similarly to the treatments, even though `Winter Density' developed the disorder 4 days before `Batavian'. The results imply that root pressure is less important than transpiration in distributing Ca to the edges of young leaves of leaf lettuce.

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Guzinski, R., M. C. Anderson, W. P. Kustas, H. Nieto et I. Sandholt. « Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day–night MODIS observations ». Hydrology and Earth System Sciences 17, n^o 7 (16 juillet 2013) : 2809–25. http://dx.doi.org/10.5194/hess-17-2809-2013.

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Abstract. The Dual Temperature Difference (DTD) model, introduced by Norman et al. (2000), uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST) to estimate surface energy fluxes. By using a time-differential temperature measurement as input, the approach reduces model sensitivity to errors in absolute temperature retrieval. The original formulation of the DTD required an early morning LST observation (approximately 1 h after sunrise) when surface fluxes are minimal, limiting application to data provided by geostationary satellites at sub-hourly temporal resolution. The DTD model has been applied primarily during the active growth phase of agricultural crops and rangeland vegetation grasses, and has not been rigorously evaluated during senescence or in forested ecosystems. In this paper we present modifications to the DTD model that enable applications using thermal observations from polar orbiting satellites, such as Terra and Aqua, with day and night overpass times over the area of interest. This allows the application of the DTD model in high latitude regions where large viewing angles preclude the use of geostationary satellites, and also exploits the higher spatial resolution provided by polar orbiting satellites. A method for estimating nocturnal surface fluxes and a scheme for estimating the fraction of green vegetation are developed and evaluated. Modification for green vegetation fraction leads to significantly improved estimation of the heat fluxes from the vegetation canopy during senescence and in forests. When the modified DTD model is run with LST measurements acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites, generally satisfactory agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the Danish Hydrological ObsErvatory (HOBE) in western Denmark, indicating realistic patterns based on land use.

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Gutiérrez, Natalia, Leyre López-de-Silanes, Carlos Escott, Iris Loira, Juan Manuel del Fresno, José Antonio Suárez-Lepe et Antonio Morata. « The Effect of Elicitors and Canopy Management in the Chemical Composition of Vitis vinifera Red Varieties in Warm and Hot Areas in Spain ». Agronomy 11, n^o 6 (10 juin 2021) : 1192. http://dx.doi.org/10.3390/agronomy11061192.

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Canopy management practices in vineyards, such as sprawling systems and shoot trimming, can change the accumulation of metabolites in grapes. The use of elicitors of biological origin on grapevines of Vitis vinifera red grape varieties may also modulate the chemical composition of the berries. These modifications are often observed in the accumulation of phenolic compounds, including pigments. Both technical approaches are alternatives involved in minimizing the effects of global climate change in warm areas. The increase of temperature related to climate change accelerates the accumulation of sugars, but produces unbalanced grapes. This work establishes the use of button sensors to monitor the climate changes occurring at grape cluster level. Together with climate monitoring, conventional instrumental analytical techniques are used to follow up the chemical composition and the phenolic fraction of grapes in four different production areas in Spain. The effect of either treatment seems variable and to be affected by external factors besides the treatment itself and the climate conditions. While there is a fine effect that correlates with the use of elicitors in varieties like Merlot and Tempranillo, there is minimal improvement observed in Tintilla de Rota. The total phenolic index increases were between 2.3% and 11.8% in the first two parcels. The same happened with the vineyard’s canopy management systems, with increased pigment accumulation and the total phenolic index rising (37.7% to 68.7%) after applying intense shoot trimming, or a variation in sugar concentrations when using sprawl conduction. This study aims to provide viticulturists and oenologists in particular, and farmers in general, with data on the field regarding the use of alternative sustainable practices in the cultivation of grapes. The techniques used involved 100% natural products without adjuvants. The benefits obtained from applying some of these practices would be to produce technically mature grapes despite climate changes, and the elaboration of more balanced wines.

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Carnevalli, Roberta Aparecida, Guilhermo Francklin de Souza Congio, André Fischer Sbrissia et Sila Carneiro da Silva. « Growth of Megathyrsus maximus cv. Mombaça as affected by grazing strategies and environmental seasonality. II. Dynamics of herbage accumulation ». Crop and Pasture Science 72, n^o 1 (2021) : 66. http://dx.doi.org/10.1071/cp20199.

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For tropical forage grasses, leaves are the main morphological component accumulated at the beginning of regrowth, and as leaf area index increases, plants change their growth pattern, allocating more resources to stem elongation as a means of optimising light capture. We hypothesised that, for Mombaça guineagrass, stem elongation and leaf senescence rate play a major role in determining net herbage accumulation rate (NHAR) and that senescence would be the key factor driving the reduction in NHAR when regrowth is interrupted beyond the critical leaf area index, that is, when canopy light interception (LI) exceeds 95%. Treatments corresponded to all combinations of two levels of pre-grazing canopy LI during regrowth (LI95% and LIMax) and two post-grazing heights (30 and 50 cm), and were allocated to experimental units according to a randomised complete block design with four replications. Measurements were performed throughout contrasting climatic conditions during four seasons from January 2001 to February 2002. Overall, spring and the two summers were the seasons when rates of leaf appearance, leaf elongation and leaf growth rate were higher, and leaf lifespan was smaller; the inverse occurred during autumn–winter. Despite the lack of statistically significant differences in NHAR between LI treatments during some seasons of the year, the ratio of leaf growth rate to NHAR was consistently higher for LI95% than LIMax. The pre-grazing target of LI95% was also efficient for decreasing stem elongation and leaf senescence rate. Increased senescence on individual tillers was the key driver generating modifications in the patterns of variation in NHAR beyond the critical leaf area index, suggesting that there is no advantage in extending the regrowth period when the main objective is to maximise leaf growth rate or NHAR.

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Narváez, Dario F., Wayne M. Jurick, James J. Marois et David L. Wright. « Effects of Surface Wetness Periods on Development of Soybean Rust Under Field Conditions ». Plant Disease 94, n^o 2 (février 2010) : 258–64. http://dx.doi.org/10.1094/pdis-94-2-0258.

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Soybean rust (SBR), caused by Phakopsora pachyrhizi, has the potential to be an economic threat to U.S. soybean production after its arrival to the continental United States in 2004. The use of fungicides to control SBR may be problematic due to the large acreage that needs to be protected, the high costs of fungicides, and the cost of application. Cultural practices such as the use of reduced seed rates, increased row widths, and row orientation to the sun have been prescribed as environmental modifications that create a microclimate less conducive to foliar disease development. Therefore, our objective was to determine the influence of different periods of leaf wetness and respective microenvironments on infection and rust development on soybean plants in the field. A misting irrigation system was developed and applied on MGV soybean for 1 min every 30 min for 0-, 6-, 12-, and 18-h periods. This study indicates that extended periods of leaf wetness (18 h) increase disease severity and the rate of spread of the disease in the upper canopy. These results, in combination with spore monitoring, may be used to refine models of pathogen reproduction, prediction, and risk in a certain regions.

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Sanchez, I., N. Zapata et J. M. Faci. « Combined effect of technical, meteorological and agronomical factors on solid-set sprinkler irrigation : II. Modifications of the wind velocity and of the water interception plane by the crop canopy ». Agricultural Water Management 97, n^o 10 (octobre 2010) : 1591–601. http://dx.doi.org/10.1016/j.agwat.2010.05.013.

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