Letteratura scientifica selezionata sul tema "Crop rotation Evaluation"

Based on a broad experimental study of crop rotation productivity in different locations of the Steppe zone, a correlative model for estimating the role of predecessors in the formation of post-crop yields has been developed. The connection between quality of agrotechnologies and change of degree of crop rotation competitiveness of culture is presented. A retrospective analysis of the efficiency of farming and crop rotation systems showed that the constant improvement of varieties and hybrids of crops and technologies for their cultivation created objective agrobiological grounds for reassessment of predecessors in crop rotation. The main motive for this transformation was that in modern agricultural systems, high-potential biotechnological resources allow to obtain higher crop yields on the worst predecessors than on the best in the past. In order to universalize the evaluation of crop rotation efficiency and model their productivity, it is proposed to introduce a crop rotation depression coefficient, which shows the share of yield remaining after individual predecessors compared to its baseline level after black fallow. The most favorable conditions developed after crops with a coefficient above 0,80 – winter wheat, barley, rape, rye, spring barley, oats. At the same time, the development of post-rotational crops was significantly inhibited by sunflower, corn for grain and silage, beets, sorghum and soybeans, their depression coef-ficient was 0,66–0,78. The proposed methodology of system analysis for the assessment of predecessors opens wider opportunities for the formation of adapted crop rotations, optimization the set of crops to market requirements, formation important adjustments to crop rotations in extreme conditions, regulation crop rotation productivity taking into account agrotechnological modernization. Keywords: crop rotation, tillage, fertilizers, crops, grain, predecessors, harvest, minimization.

The nature of subjective positioning on the role of crop rotations in agriculture from many points of view, namely – agrochemical, biological, geological and energetic. This leads to the belief that crop rotation arose as a need for reasonable human interaction with nature, a careful attitude to it. However, a comprehensive ecological and biosphere approach to understanding the essence of crop rotation requires the resolution of certain contradictions that arise in the implementation of modern farming systems. Based on the data of long-term feld experiments, the main indicators of the biological cycle of humus carbon in black soil are calculated. The calculation is based on the balance of humus as the difference between the fnal and initial content and reserves in the soil under different crop rotations. We found that the joint application of organic and mineral fertilizers had a positive effect on the balance of humus and nitrogen in the soil and, ultimately, on crop yields and crop rotation productivity. Against this background, a positive balance of humus (+1.29 t/ha) and total nitrogen (+80 kg/ha) in the soil is observed. Strengthening the organic fertilizer system by using, in addition to manure, by-products of crops – cereal straw, peas, corn stalks contributed to the formation of a positive balance of humus and nitrogen in the soil: the annual accumulation of humus was 0.28 t/ha, nitrogen 14 kg/ha. Due to the humifcation of crop residues of cereals, peas and perennial legumes during the 7-year study period in the soil of control crop rotation 1 formed humus 2.85 t/ha, in crop rotation 14 with grasses – 7.0, the rest of crop rotations – from 3.4 up to 4.0 t/ha. In general, 5.5 % of the initial stock of humus or 8.9 t/ha was mineralized in the crop rotation without fertilizers during the specifed period. If we add to this about 3 t/ha of humus, the decomposition of which in the process of mineralization was compensated by plant residues, then during this period decomposed about 12 t/ha of humus. This value of mineralization characterizes the parameters of the biological cycle of humus in the control crop rotation. Key words: soil, fertilizers, crop rotations, crop yield, crop rotation productivity, plant residues, humifcation, humus, humus mineralization, humus balance.

Cropping systems greatly impact the productivity and resilience of agricultural ecosystems. However, we often lack an understanding of the quantitative interactions among social, economic and ecological components in each of the systems, especially with regard to crop rotation. Current production systems cannot guarantee both high profits in the short term and social and ecological benefits in the long term. This study combined statistic and economic models to evaluate the comprehensive effects of cropping systems on rice production using data collected from experimental fields between 2017 and 2018. The results showed that increasing agricultural diversity through rotations, particularly potato–rice rotation (PR), significantly increased the social, economic and ecological benefits of rice production. Yields, profits, profit margins, weighted dimensionless values of soil chemical and physical (SCP) and heavy metal (SHM) traits, benefits and externalities generated by PR and other rotations were generally higher than successive rice cropping. This suggests that agricultural diversity through rotations, particularly PR rotation, is worth implementing due to its overall benefits generated in rice production. However, due to various nutrient residues from preceding crops, fertilizer application should be rationalized to improve the resource and investment efficiency. Furthermore, we internalized the externalities (hidden ecological and social benefits/costs) generated by each of the rotation systems and proposed ways of incenting farmers to adopt crop rotation approaches for sustainable rice production.

Theory and models of crop yield loss from weed competition have led to decision models to help growers choose cost-effective weed management. These models are available for multiple-species weed communities in a single season of several crops. Growers also rely on crop rotation for weed control, yet theory and models of weed population dynamics have not led to similar tools for planning of crop rotations for cost-effective weed management. Obstacles have been the complexity of modeling the dynamics of multiple populations of weed species compared to a single species and lack of data. We developed a method to use limited, readily observed data to simulate population dynamics and crop yield loss of multiple-species weed communities in response to crop rotation, tillage system, and specific weed management tactics. Our method is based on the general theory of density dependence of plant productivity and extensive use of rectangular hyperbolic equations for describing crop yield loss as a function of weed density. Only two density-independent parameters are required for each species to represent differences in seed bank mortality, emergence, and maximum seed production. One equation is used to model crop yield loss and density-dependent weed seed production as a function of crop and weed density, relative time of weed and crop emergence, and differences among species in competitive ability. The model has been parameterized for six crops and 15 weeds, and limited evaluation indicates predictions are accurate enough to highlight potential weed problems and solutions when comparing alternative crop rotations for a field. The model has been incorporated into a decision support tool for whole-farm management so growers in the Central Great Plains of the United States can compare alternative crop rotations and how their choice influences farm income, herbicide use, and control of weeds in their fields.

Accurate information of crop rotation in large basin is essential for policy decisions on land, water and nutrient resources around the world. Crop area estimation using low spatial resolution remote sensing data is challenging in a large heterogeneous basin having more than one cropping seasons. This study aims to evaluate the accuracy of two phenological datasets individually and in combined form to map crop rotations in complex irrigated Indus basin without image segmentation. Phenology information derived from Normalized Difference Vegetation Index (NDVI) and Leaf Area Index (LAI) of Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, having 8-day temporal and 1000 m spatial resolution, was used in the analysis. An unsupervised (temporal space clustering) to supervised (area knowledge and phenology behavior) classification approach was adopted to identify 13 crop rotations. Estimated crop area was compared with reported area collected by field census. Results reveal that combined dataset (NDVI*LAI) performs better in mapping wheat-rice, wheat-cotton and wheat-fodder rotation by attaining root mean square error (RMSE) of 34.55, 16.84, 20.58 and mean absolute percentage error (MAPE) of 24.56 %, 36.82 %, 30.21 % for wheat, rice and cotton crop respectively. For sugarcane crop mapping, LAI produce good results by achieving RMSE of 8.60 and MAPE of 34.58 %, as compared to NDVI (10.08, 40.53 %) and NDVI*LAI (10.83, 39.45 %). The availability of major crop rotation statistics provides insight to develop better strategies for land, water and nutrient accounting frameworks to improve agriculture productivity.

The root lesion nematode, Pratylenchus neglectus, is one of the most damaging nematodes to affect wheat worldwide. The nematode is widely distributed in Montana, primarily affecting winter wheat within the state. Managing the nematode primarily involves rotation to resistant and moderately resistant crops (peas, lentils, and barley). A nematode survey was conducted across the state nearly 10 years after an initial survey, to reassess the nematode threat and assess the impact of changing trends in crop rotations. To assess the broad applicability of rotation crops to control P. neglectus across Montana, greenhouse trials were conducted to challenge rotational crops using eight populations of P. neglectus collected from geographically diverse locations across the state. In the trials, conducted with four Montana crops, a significant interaction was detected between crop and nematode population (analysis of variance P < 0.001). Populations from Hill, Dawson, and Chouteau counties were found to be pathogenic on barley. Male nematodes were detected in seven of the eight pot culture populations, and these were confirmed to be P. neglectus by morphological and molecular methods. These results suggest a re-evaluation of barley and lentils as a management option for P. neglectus in Montana, as pathotypes for each exist within the state.

SUMMARYIn recent years, simulation models have been used as a complementary tool for research and for quantifying soil carbon sequestration under widely varying conditions. This has improved the understanding and prediction of soil organic carbon (SOC) dynamics and crop yield responses to soil and climate conditions and crop management scenarios. The goal of the present study was to estimate the changes in SOC for different cropping systems in West Africa using a simulation model. A crop rotation experiment conducted in Farakô-Ba, Burkina Faso was used to evaluate the performance of the cropping system model (CSM) of the Decision Support System for Agrotechnology Transfer (DSSAT) for simulating yield of different crops. Eight crop rotations that included cotton, sorghum, peanut, maize and fallow, and three different management scenarios, one without N (control), one with chemical fertilizer (N) and one with manure applications, were studied. The CSM was able to simulate the yield trends of various crops, with inconsistencies for a few years. The simulated SOC increased slightly across the years for the sorghum–fallow rotation with manure application. However, SOC decreased for all other rotations except for the continuous fallow (native grassland), in which the SOC remained stable. The model simulated SOC for the continuous fallow system with a high degree of accuracy normalized root mean square error (RMSE)=0·001, while for the other crop rotations the simulated SOC values were generally within the standard deviation (s.d.) range of the observed data. The crop rotations that included a supplemental N-fertilizer or manure application showed an increase in the average simulated aboveground biomass for all crops. The incorporation of this biomass into the soil after harvest reduced the loss of SOC. In the present study, the observed SOC data were used for characterization of production systems with different SOC dynamics. Following careful evaluation of the CSM with observed soil organic matter (SOM) data similar to the study presented here, there are many opportunities for the application of the CSM for carbon sequestration and resource management in Sub-Saharan Africa.

AbstractAn evaluation of agricultural systems often involves multidisciplinary teams that include crop scientists, animal scientists, soil scientists, pest control specialists, agricultural economists, and others. Agricultural economists can improve the technical quality and comprehe nsiveness of agricultural systems research in six major areas: budgeting and investment analyses; whole-farm and institutional factors; risk considerations; aggregate effects on crop and livestock prices; society-wide welfare effects of technical or policy changes; and economic values of environmental and other nonmarket effects. Economic analysis has been part of several successful multidisciplinary research efforts in the United States Pacific Northwest. These have covered soil conservation, integrated pest management, sustainable agriculture, crop rotation choice, and beef ranch management. As an example of institutional influences on economic outcomes, one study showed that the structure and selectivity of United States commodity programs have favored conventional over low-input rotations. Regarding risk management, an appropriate “package system” including conservation tillage, a diversified crop rotation, and adequate chemical weed management was shown both to sustain profitability and to reduce income fluctuations. Properly designed economic analysis can make similar contributions to identifying successful dryl and agricultural technologies throughout the world.

Evaluation of Adaptive Measures to Reduce Climate Change Impact on Soil Organic Carbon Stock In Žitný Ostrov RegionClimate change impacts on soil organic carbon sequestration rate were simulated by agroecological model DAISY. Daily meteorological data for the Danubian Lowland up to 2100 were generated according to emission scenarios SRES A2 and B1 using general circulation model CGCM3.1. Effect of gradual increase of CO2concentration in the atmosphere was taken into account. Various crop rotations as well as various management practices including irrigation and crop residuals incorporation were considered in three variants: i/ rainfed, residuals not incorporated, ii/ irrigated, residuals not incorporated, iii/ summer crops irrigated and residuals incorporated. Modelling outputs confirm that conventional rainfed agro-technical practices without incorporation of crop residues resulted to significant loss of soil organic carbon in soil profile towards more distanced time slices. The irrigation and the incorporation of crop residuals including stems and leaves can reduce soil organic carbon losses. If it is combined with proper crop rotation the soil organic carbon stock in soil profile can even increase.

Indigenous African shifting cultivation production systems, that were developed over many generations and took into account production potential as well as the constraints imposed by natural resources, are no longer practicable for Nigerian smallholder farmers. These systems relied on long fallow for fertility restoration after a period of cropping. Overpopulation has resulted in lower per capita land availability, necessitating a shift to sedentary cultivation systems. In such systems, fallow is short term (months) compared to shifting systems, where it lasted several years. This shift has resulted in overexploitation of land resources and despite intensification of agricultural production methods, non-sustainable demand on the natural resource base has increased and crop and animal production has declined. This study examined the performance of five maize-based cropping systems consisting of cereal-legume, cereal-cereal and cereal bare fallow rotations, to identify systems that have potential for increased agricultural production in the subhumid and mid-altitude zones of Nigeria. The study was conducted at Richmond, near Sydney, in NSW, Australia from 2000 to 2003. The trial investigated the effects of the combined use of legumes and N fertilizer in CSs to maintain or improve soil fertility, maize crop and maize storage silage production and yield and quality of all crop residues. This study showed that inclusion of a legume in the rotation is an important production and income generating strategy. Owing to their potential for increased maize productivity, to build up N-rich systems and to improve small holder levels of farm income, cropping systems with legumes should therefore be given more research attention in Nigeria
Doctor of Philosophy (PhD)

Five different crops were evaluated in exploratory and observational field studies for potential use as a summer cover crop in a rotation with commonly grown vegetable and field crops. Sesbania ( Sesbania exaltata), cowpea (ViRna unguiculata), sunnhemp (Crotalaria iuncea var. Tropic Sun), sudangrass (Sorghum sudanense cv. Piper), and kenaf (Hibiscus cannabinus) were drill seeded and grown with 2-3 irrigations during the summer months in two field tests. In one test, fresh weight yields were: 7,794 lb/A for sesbania; 10,551 lb/A for sunnhemp; 5,184 lb/A for cowpea; 19,816 lb/A for sudangrass; and 2,390 lb/A for kenaf General observations indicated that adult whiteflies were attracted to sunnhemp at one test site but not at the other. Broccoli, cabbage, and barley were planted in the fall following the cover crops and general observations indicated that sudangrass significantly reduced all of the crops' stand and measurable responses were not evident where the other cover crops were planted.

I have worked on a Case-Based Reasoning (CBR) system that evaluates crop rotations for their soil erosion and risk of insect pest problems. The purpose of this system is to provide decision support for an automated whole-farm planner (CROPS). CROPS (Buick et al., 1992) generates crop rotation plans that can address some of the environmental, economic and legislative pressures facing natural resource managers. To generate and recommend a crop rotation plan CROPS requires estimates on the soil erosion risks and pesticide pollution potential of the crop rotation. In this research I have designed and prototyped a system that can assist CROPS in the process of whole-farm planning by providing information required for determining the soil erosion risks and the pesticide pollution potential of crop rotations. Inputs for the system include: a crop rotation, its tillage and residue management practices, and field conditions. Soil erosion risk is quantified using the C-value. Pest risks are likelihood of pest outbreaks that require control in a crop rotation. CBR was the chosen methodology for system implementation. In CBR, solutions to new problem situations are derived from retrieving and adapting solutions to similar problem situations experienced in the past. The system was prototyped using Esteemâ ¢, a CBR development shell, and runs on a PC under the MS. Windowsâ ¢, operating system.
Master of Science

Onion production in the United States is seriously affected by the tospovirus Iris Yellow Spot (IYSV), whose symptoms include lenticular-shaped lesions that reduce photosynthesis and bulb yield. Thrips tabacai Lindeman, onion thrips (OT), is the only known vector of the disease and a primary arthropod pest of onion. Frequent insecticide applications, increasing resistance in OT populations to insecticides, high nitrogen (N) fertilization rates and loss of yield to disease and insect pressure threaten sustainable onion production. The objectives of this study were to identify crop management strategies to enhance onion productivity while suppressing OT and IYSV. Three fertilizer rates and two crop rotations were assigned to replicated plots to assess effects on onion growth, yield, bulb storage quality, soil quality, thrips populations and IYSV incidence. Trap crops of carrot, buckwheat and lacey phacelia were established in commercial fields to evaluate impact on thrips populations and IYSV occurence. Reduced nitrogen (N) rates, one-third the standard grower rate (133.8 kg N ha-1), resulted in no yield loss as compared with the standard N rate, despite slower crop maturation. Onions treated with a standard N rate(401.8 kg N ha-1) had greater numbers of adult and immature OT than other treatments. Soil nitrate levels were lower and microbial activity measured as dehydrogenase and biomass were greater in reduced N treatments. Plots with buckwheat and phacelia had greater numbers of both adult and immature OT when trap crop apparancy was high (i.e. when onion plants were relatively smaller). There was no observed effect of trap crops on IYSV levels. Results suggest that reduced rate N applications lower numbers of OT while enhancing the microbial population, reducing potential for nitrate leaching while still maintaining yields. Potential for trap crops of buckwheat and lacey phacelia to attract onion thrips from onions exists with successive stands of highly apparent trap crops.

In 1986, Egypt implemented a succession of comprehensive economic reforms both in the agriculture sector and more generally such as the Economic Reform and Structural Adjustment Program (ERSAP) of 1991. Since then, the agricultural sector has been gradually transformed from one characterised by central planning and governmental controls to one that is more free market oriented. This study employs the Policy Analysis Matrix technique to evaluate the impacts of reform policies on eleven major crops (wheat, maize, sugar cane, soy bean, broad bean, cotton, rice, tomatoes, potatoes, long and short berseem) and their associated crop rotations (crop mix) during the period 1986-2000. The PAM offers six tools of economic indicators. The first (private Cost Ratio) is used to identify the competitiveness of crops domestically. The second (Domestic Resource Cost) is employed in an attempt to identify those commodities in which Egypt has a comparative advantage/disadvantage. The third (Nominal Protection Coefficient for inputs and outputs) is used to measure the divergences between the domestic and international prices for inputs and output. The fourth (Effective Protection Coefficient) reflects the complete pattern of incentives to farmers in the tradable commodities markets, combining the separate influences of polices represented by the NPCO and NPCI measures. The fifth and sixth (profitability Coefficient and Subsidy Ratio to Producers) estimates the net protection effects afforded to each of the major sectors by the whole range of policy intervention. The most important findings are that: (1) The Egyptian pricing policy in the reform era is still encouraging domestic production of importable products (by setting their prices above world prices) while export products are taxed relative to their equivalent world prices. (2) Cotton, the main historical export commodity, is shown to be grown with a comparative disadvantage since it receives the highest levels of subsidy. (3) On the other hand, wheat showed a remarkably positive example for the high response from farmers to the reformed pricing policies with an increase in its area and its productivity by 83% and 60% respectively. (4) There is a high response of change in planted area to water charges. The conclusion of these analyses is that the impact of policy changes has indeed been positive, especially in relation to areas of crop production. But many remains to be done, for example, growers' still face problems in marketing, accessing to inputs, processing and trade.

Thesis (MScAgric)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The aim of this study was to investigate the influence of crop rotation and soil tillage on the soil water balance and water use efficiency of wheat, canola, lupin and medics in the Swartland sub region of the Western Cape. This trail was conducted as a component study within a long-term crop rotation/tillage trial during 2012 and 2013 at the Langgewens Research Farm (33016’42.33” S; 18042’11.62” E; 191m) of the Western Cape Department of Agriculture near Moorreesburg. The experiment was laid out as a randomized complete block, with a split-plot treatment design and replicated four times. Three crop rotation systems, continues wheat (WWWW), wheat/medic/wheat/medic (WMcWMc) and wheat/canola/wheat/lupin (WCWL) were allocated to main plots. . Each main plot was subdivided into four sub-plots allocated to four tillage treatments namely: zero-till (soil left undisturbed and planted with zero-till planter), no-till (soil left undisturbed until planting and then planted with a tined no-till planter), minimum-till (soil scarified March/April and then planted with a no-till planter) and conventional tillage (soil scarified late March/early April, then ploughed and planted with a no-till planter). All straw, chaff and stubble remained on the soil surface and no-grazing was allowed on all tillage treatments. Three replicates were included in this current study. Only the no-till (NT) and conventional till (CT) were included in this current study as main tillage treatments. The volumetric soil water content was monitored at weekly intervals during the active growing season (May-October) and once a month during the fallow period (November-April) using a Diviner 2000 soil moisture meter. The Diviner 2000 was used to record the soil water content at every 100 mm depth increment up to the maximum depth of the profile. At the end of the growing season the total biomass, grain yield and quality parameters were determined. The soil water balance data calculated from the 2012 season were found to be inconclusive due to too shallow installation of soil water monitoring tubes and big variations in the depth complicating any attempt in comparing data from treatments and cropping systems. Soil water monitoring tubes was installed to a depth of 900 mm in the 2013 season. Complications during planting in the 2013 season resulted in very poor emergence in the CT sites. Weed counts revealed that only 38 % of CT sites were covered by crop, 31 % with weeds and 31 % were completely bare. The NT sites had 40 % crop coverage, 50.5 % grass weed coverage and only 9.5% bare surface. As a consequences crop rotation had no effect on the soil water balance, while the tillage treatments showed a response. The effect that tillage had on the soil water balance was clearly shown in the 2013 season, in which 79 mm more rainfall occurred than the long-term average. NT retained more soil water in the profile in the drier first half of the season when only 30 % of the total rainfall in the 2013 season occurred. There was no real difference in the soil water retention in the second half of the season where 70 % of the total rainfall in the 2013 season occurred. Crop rotation did have a positive effect on grain yield. Wheat monoculture was out performed by legume based cropping systems. This trend was also observed in the biomass production. No significant difference between tillage treatments were recorded when comparing grain yield data. However wheat mono culture was again out-performed by the McWMcW, CWLW and LWCW systems producing on average significantly higher biomass. The data from both seasons suggest that in seasons where more rainfall than the long term average occurs, there is no difference in the RUE between cropping systems or tillage practices.. This study highlighted the major effect that the prevailing weather conditions have and that the expected advantages associated with NT most likely only come into play in dry conditions when plant water availability is limited.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die invloed van grondbewerking en gewasproduksiestelsels op die grondwaterbalans en doeltreffendheid van watergebruik te ondersoek in die koringproduserende gebied van Malmesbury. Hierdie eksperiment is uitgevoer as 'n komponentstudie binne 'n langtermyn grondbewerking/gewasrotasieproef gedurende 2012 en 2013 op die Langgewens Navorsingsplaas (33016'42 .33 'S; 18042'11 0,62' E, 191m) van die Wes-Kaapse Departement van Landbou naby Moorreesburg. Die eksperiment is uitgelê as 'n volledige ewekansige blok, met 'n gesplete perseel behandelingsontwerp met vier herhalings. Drie gewasproduksiestelsels naamlik, koring monokultuur (WWWW), koring/medic/koring/medic (WMcWMc) en koring/canola/ koring/lupiene (WKWL) is elk toegeken aan persele en vier keer herhaal. Elke hoofperseel is onderverdeel in vier subpersele en bewerkingsbehandelings is soos volg toegeken: Konvensionele bewerking (CT) - grond gebreek in Maart/April, en daarna geploeg en geplant met geen bewerkingsplanter. Minimum bewerking (MT) - grond gebreek in Maart/April en daarna geplant met 'n geen bewerkingsplanter. Geen bewerking (NT) - grond is heeltemal onversteur gelaat tot planttyd en daarna geplant met 'n geen bewerkingsplanter. Zero bewerking (ZT) - grond tot planttyd met rus gelaat en dan geplant met 'n sterwielplanter. Alle strooi, kaf en stoppels het op die grondoppervlak gebly en geen beweiding is toegelaat nie. Slegs drie herhalings is ingesluit in die huidige studie en slegs die geen bewerking (NT) en konvensionele bewerking (CT) is in die huidige studie as hoof bewerkingbehandelings ingesluit. Die volumetriese grondwaterinhoud is weekliks gemonitor tydens die aktiewe groeiseisoen (Mei - Oktober) en een keer 'n maand gedurende die braaktydperk (November - April) met behulp van 'n Diviner 2000 grondvogmeter. Die Diviner 2000 is gebruik om die grondwaterinhoud by elke 100 mm diepte tot die maksimum diepte van die profiel te bepaal. Aan die einde van die seisoen is die totale biomassa, graanopbrengs en kwaliteitparameters bepaal. Die data vir grondwaterbalans van die 2012-seisoen is buite rekening gelaat weens te vlak installering van moniteringsbuise en groot variasie in die dieptelesings wat enige poging om vergelykende data van rotasie en behandelings te verkry, bemoeilik het. Moniteringsbuise vir grondwater is geïnstalleer tot op 'n diepte van 900 mm in die 2013-seisoen. Komplikasies tydens die plantaksie in die 2013-seisoen het gelei tot 'n baie swak opkoms in die CT-persele. Slegs 38 % van die CT-persele was bedek deur die gewas en 31 % met onkruid, terwyl 31 % van die oppervlak onder CT-behandeling heeltemal kaal was. Die NT-persele het 40 % gewasbedekking, 50.5 % grasbedekking en slegs 9.5 % kaal oppervlak gehad. Dit het die poging, om die effek van wisselboustelsels op die grondwaterbalans, in die wiele gery. Alhoewel wisselbou skynbaar geen effek op die grondwaterbalans gehad het nie, het die tipe bewerking egter wel ‘n effek gehad. Die effek van grondbewerking op die grondwaterbalans het duidelik na vore gekom in die 2013-seisoen. In hierdie seisoen het 79 mm meer reën geval as die langtermyngemiddelde. Geen bewerking het meer grondwater in die droër eerste helfte van die seisoen in die profiel behou, toe slegs 30% van die totale reënval in die 2013 geval het. Daar was geen beduidende verskil in die grondwaterretensie in die tweede helfte van die seisoen toe 70% van die totale reënval in die 2013 geval het nie. Wisselbou het egter 'n positiewe uitwerking op die graanopbrengs gehad. Koring monokultuur is in opbrengsyfers geklop deur stelsels met peulplante as komponent. Hierdie tendens is ook waargeneem in die biomassaproduksie. Bewerkingsbehandelings het geen beduidende verskil in graanopbrengste tot gevolg gehad nie, hoewel die biomassaproduksie van koring monokultuur weer geklop is deur die McWMcW-, CWLW- en LWCW-stelsels. Die data van beide seisoene dui daarop dat in seisoene waar meer reën as die langtermyn gemiddelde voorkom, daar geen verskil in die RUE tussen verbouingstelsels of bewerkingspraktykes was nie. Hierdie studie beklemtoon die groot invloed wat die heersende klimaat speel en dat die verwagte voordele wat verband hou met NT waarskynlik slegs ‘n rol speel in droër jare.

The purpose of this thesis is the determination of a minimum market price for Short-Rotation Forestry (SRF) willow biomass grown in monoculture and windbreaks in Quebec and Ontario. Full cost budgeting was used and developed on a Microsoft Excel spreadsheet. Harvest cycles of 3 and 4 years for monoculture plantations, and 8 years for windbreaks were investigated. Estimates for establishment and other preharvest costs were obtained from mid-sized (5 hectares) commercial SRF willow plots in Quebec and Ontario.
For the monoculture plantations, irrespective of cycle length, and using the base case figures, the final delivery cost of willow biomass ranged between 74-126 $/odMg and 63--109 $/odMg based on current and projected costs respectively. These hold for yields between 7 and 11 odMg/ha/yr. Moreover, the 4-year cycle was revealed to be more economically efficient than a 3-year cycle. Along with yield, the main cost factors affecting the economics of SRF monoculture plantations are: harvesting, transportation to a processing plant, land lease management. For the two major energy markets, ethanol and electricity production (biomass in replacement of coal), SRF willow biomass in monoculture plantations does not appear to be a viable feedstock given present technology and yields. In the short run, a more promising outlet for willow biomass is space heat production for small buildings, farm complexes, etc. In this market, many potential buyers can afford to pay a higher price for biomass than ethanol or electricity utilities.
In the windbreak system, biomass could be produced for between 44 and 68 $/odMg, assuming that yields between 12 to 20 odMg/ha/yr can be achieved. At this price, windbreak biomass is not a competitive feedstock for ethanol or electricity generation, but is attractive for space heat production. (Abstract shortened by UMI.)

The objective of this research was to determine the effects of conventional inputs on soil chemical and biological properties compared to organic systems in a four year vegetable rotation. Tillage and cover crops were the same in all treatments to avoid confounding factors often present in similar research. Additional experiments investigated plant gene expression in organic and conventional management systems and in soils with decreased microbial diversity. Experimental plots were prepared in the spring of 2004; four replications of three management treatments, organic, low-input and conventional, were arranged in a randomized complete block design. The rotation consisted of edamame soybean, sweet corn, fallow (pastured poultry in organic plots), and potatoes. Soil samples were taken in the spring and fall of each year, along with data for pest damage, weed control, yield and quality. Soil samples were analyzed for enzyme activity (maximum activity under substrate saturation) and basic soil chemical properties. Treatments were compared over time using 2-Way ANOVA. Multiplex terminal-restriction fragment length polymorphism (M-TRFLP) profiles of the soil microbial community were compared using Multiple Response Permutation Procedures (MRPP). Multi-way ANOVA detected significant treatment effects over time in total carbon, nitrogen, Mehlich III K, Exchangeable K and exchangeable Na (p=0.05). Many significant changes in soil properties over time could not be attributed to treatment effects. All treatments produced similar yields, indicating that successful organic production of these vegetables is possible in Kentucky. Input costs for organic were 37% higher than conventional, due to the cost of organic fertilizer. The organic system required nearly 50% more labor hours than conventional or low-input. The low-input system was the most cost effective, with 58% less input expenses than the conventional system. Microarray analysis of approximately 37,500 Glycine max transcripts did not show significant differences in the gene expression between plants grown organically and conventionally, in plots with significant soil chemical and microbial differences. An experiment in progress is investigating changes in plant gene expression using real time RT-PCR in tomatoes grown in autoclaved soil and native field soil.

Here, we present a survey on the evaluation of broad-spectrum fungicides efficacy against cucumber powdery mildew and ascochyta leaf spot. A high efficiency of “Cidely Top 140”, DС (0.1 %) and “Luna Experience”, CS (0.06 %) against powdery mildew was determined. Biological efficacy of these fungicides was 70.9–92.4 % and 73.1–95.3 % after application in the first and second crop rotation, respectively. Plants treatment by “Cidely Top 140”, DС (0.1 %) and “Miravis”, SC (0.05 %) at early stages of ascochyta leaf spot inhibited the disease at the depressive level (2.5–4.8 %) notwithstanding the season of the crop growing.

Research was carried out at the Lithuanian Research Centre for Agriculture and Forestry’s (LAMMC) Joniškėlis Experimental Station on a clay loam Endocalcari Endohypogleyic Cambisol. The study was aimed to explore the aboveground mass of perennial forage legumes: red clover (Trifolium pratense L.) and lucerne (Medicago sativa L.), and their mixtures with festulolium (x Festuliolium), used as green manure, qualitative parameters and compatibility with cereals on the basis of nutrients nitrogen (N), phosphorus (P) and potassium (K). The deficiency of other nutrients (P, K) and intensity of green manure mineralization can lead to N absorption. It has been determined that winter wheat takes one kg of N together with 0.2 kg P and 0.6 kg K. Spring wheat requires a similar amount of P but a higher amount of K. Average winter wheat grain yield can be 4.0 t ha-1 on a clay loam Cambisol in organic cropping system. NPK content – 134 kg ha-1 is needed for such productivity (grain + straw). This content is lower for spring winter growing. P:N and K:N ratios are more favourable in perennial forage legume mixture with festulolium, as compared to legume alone. To obtain grain yields of 4 t ha-1 of winter wheat and 3 t ha-1 of spring wheat in balanced organic crop rotation it is sufficient to apply 3.0 and 2.0 t ha-1 DM of pure legume mass as green manure. “Cut-and-carry” fertilisers do not satisfy the wheat demand for P.

Due to their great potential for fuel saving, Contra-Rotating Open Rotors (CRORs) receive renewed interest by the airframers and the engine manufacturers. The inherent high efficiency of this propulsion system, however, is potentially offset by the level of noise emitted by the open blades. The acoustic impact on passengers and community may represent a major issue to their environmental acceptance. Fast and robust noise prediction tools are clearly required to support the development of quieter propellers and their integration in future civil aeronautical transport. The most common strategy for noise estimation consists in a two-step approach, based on the Lighthill analogy: unsteady near-field aerodynamic flow simulation to evaluate the noise sources, coupled to a far-field acoustic propagation code. Focus is given here on two structured grid flow solvers employed to investigate a scale-model of a 12×10 pusher CROR. The unsteady aerodynamic three-dimensional flow is indeed computed for typical cruise conditions using both the nonlinear harmonic method (NLH) of FINE™/Turbo software and elsA’s chorochronic technique. The evaluation of the far-field noise based on the aerodynamic fields is then carried out with the KIM code, Onera’s acoustic propagation code based on the Ffowcs-Williams and Hawkings (FW-H) formulation. The obtained results enable an analysis of the complex aerodynamic interactions between the two propellers that generate interaction tones in the acoustic signature of the propulsion system. A comparison in terms of numerical settings, computational costs and flow fields is performed between the two CFD methods, which show an excellent match of the predicted global performance of the propulsion system. Some differences in the predicted acoustic signatures are discussed in the paper.