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Wheat Yield (wheat + yield)
Selected AbstractsAssessing the results of scenarios of climate and land use changes on the hydrology of an Italian catchment: modelling studyHYDROLOGICAL PROCESSES, Issue 19 2010Daniela R. D'Agostino Abstract Hydrological models are recognized as valid scientific tools to study water quantity and quality and provide support for the integrated management and planning of water resources at different scales. In common with many catchments in the Mediterranean, the study catchment has many problems such as the increasing gap between water demand and supply, water quality deterioration, scarcity of available data, lack of measurements and specific information. The application of hydrological models to investigate hydrological processes in this type of catchments is of particular relevance for water planning strategies to address the possible impact of climate and land use changes on water resources. The distributed catchment scale model (DiCaSM) was selected to study the impact of climate and land use changes on the hydrological cycle and the water balance components in the Apulia region, southern Italy, specifically in the Candelaro catchment (1780 km2). The results obtained from this investigation proved the ability of DiCaSM to quantify the different components of the catchment water balance and to successfully simulate the stream flows. In addition, the model was run with the climate change scenarios for southern Italy, i.e. reduced winter rainfall by 5,10%, reduced summer rainfall by 15,20%, winter temperature rise by 1·25,1·5 °C and summer temperature rise by 1·5,1·75 °C. The results indicated that by 2050, groundwater recharge in the Candelaro catchment would decrease by 21,31% and stream flows by 16,23%. The model results also showed that the projected durum wheat yield up to 2050 is likely to decrease between 2·2% and 10·4% due to the future reduction in rainfall and increase in temperature. In the current study, the reliability of the DiCaSM was assessed when applied to the Candelaro catchment; those parameters that may cause uncertainty in model output were investigated using a generalized likelihood uncertainty estimation (GLUE) methodology. The results showed that DiCaSM provided a small level of uncertainty and subsequently, a higher confidence level. Copyright © 2010 John Wiley & Sons, Ltd. [source] Assessment of the water,salinity crop production function of wheat using experimental data of the Golestan province, Iran,IRRIGATION AND DRAINAGE, Issue 4 2009A. R. Kiani stress hydrique; stress de salinité; fonctions de production; blé Abstract Optimisation of agricultural water management in arid and semi-arid regions requires the availability of water,salinity crop production functions. A two-year experiment was conducted in the northern Golestan province of Iran to assess the water,salinity production function of wheat. The treatments in the experiment consisted of four levels of irrigation water, i.e. 50 (W1), 75 (W2), 100 (W3) and 125 (W4) % of crop water requirement, and four levels of water salinity, respectively 1.5 (S1), 8.5 (S2), 11.5 (S3) and 14.2 (S4) dS,m,1. The plots were arranged in a randomised complete block design with three replications and water quantity as main plot treatment and water quality as subplot treatment. The data were analysed using linear, quadratic, Cobb,Douglas and transcendental functions, complemented with an economic analysis. The results indicate that for the given climate,soil conditions, transcendental functions best predict wheat yield under both water and salinity stress conditions. Yield reduction caused by a unit increase of matric potential is found to be larger than that caused by a unit increase of osmotic potential. The marginal rate of technical substitution indicates that each one of the two factors studied, namely soil salinity and water supply, can be substituted with the other in a wide range in order to achieve equal amount of yield. Copyright © 2008 John Wiley & Sons, Ltd. L'optimisation de la gestion de l'eau agricole dans les zones arides et semi-arides nécessite de savoir la relation entre l'apport d'eau selon sa salinité et la production végétale. Une expérience de deux ans a été menée dans le nord de la province du Golestan en Iran pour évaluer la fonction de production de l'eau saline sur le blé. Les traitements expérimentaux consistaient en quatre niveaux d'apports d'eau soit 50% (W1), 75% (W2), 100% (W3) et 125% (W4) des besoins en eau des cultures, et quatre niveaux de salinité de l'eau, respectivement 1.5 (S1), 8.5 (S2), 11.5 (S3) et 14.2 (S4) dS,m,1. Les parcelles ont été disposées dans un bloc de Fisher randomisé avec trois répétitions avec la quantité de l'eau comme variable principale et la qualité de l'eau comme variable secondaire. Les données ont été analysées en utilisant les fonctions linéaires, quadratiques, Cobb,Douglas et transcendantes, complétées par une analyse économique. Les résultats indiquent que, pour un climat et un état du sol donnés, les fonctions transcendantes donnent les meilleures prédictions du rendement de blé en condition de salinité et de stress hydrique. La baisse de rendement causée par une augmentation d'une unité de potentiel hydrique est plus importante que celle causée par l'augmentation d'une unité de potentiel osmotique. Le taux marginal de substitution technique indique que chacun des deux facteurs étudiés, à savoir la salinité des sols et l'apport d'eau, peuvent être largement substitués l'un à l'autre pour viser rendement identique. Copyright © 2008 John Wiley & Sons, Ltd. [source] Environmental and genetic determination of protein content and grain yield in durum wheat under Mediterranean conditionsPLANT BREEDING, Issue 5 2001Y. Rharrabti Abstract The unpredictability of the Mediterranean climate causes fluctuations in wheat yield and quality, but offers the opportunity for obtaining high-quality durum wheat in terms of grain protein content. Twenty-five durum wheat genotypes were grown under irrigated and rainfed conditions at each of two latitudes in Spain during 1998 and 1999. Differences between latitudes in grain protein content and chlorophyll content in the flag leaf were attributable to nitrogen fertilization management. Cycle length until anthesis was less affected by the environment than grain-filling duration, and was longer under irrigated conditions than in the rainfed sites. A negative asymptotic curve was the best equation to fit the relationship between yield and protein content, suggesting that yield improvements in fertile environments may be attained with negligible reductions in protein content. ,Jabato', ,Waha', ,Lagost-3', ,Massara-1' and ,Vit,on' showed medium to high yield, yield stability and high protein content. Chlorophyll content in the flag leaf, measured at anthesis with the soil-plant analysis development (SPAD) portable field unit, may be useful for the fast and cheap detection of durum wheat genotypes with high grain protein content in drought-stressed Mediterranean environments. [source] Managing precipitation use in sustainable dryland agroecosystemsANNALS OF APPLIED BIOLOGY, Issue 2 2004GARY A PETERSON Summary In the Great Plains of North America potential evaporation exceeds precipitation during most months of the year. About 75% of the annual precipitation is received from April through September, and is accompanied by high temperatures and low relative humidity. Dryland agriculture in the Great Plains has depended on wheat production in a wheat-fallow agroecosystem (one crop year followed by a fallow year). Historically this system has used mechanical weed control practices during the fallow period, which leaves essentially no crop residue cover for protection against soil erosion and greatly accelerates soil organic carbon oxidation. This paper reviews the progress made in precipitation management in the North American Great Plains and synthesises data from an existing long-term experiment to demonstrate the management principles involved. The long-term experiment was established in 1985 to identify dryland crop and soil management systems that would maximize precipitation use efficiency (maximization of biomass production per unit of precipitation received), improve soil productivity, and increase economic return to the farmers in the West Central portion of the Great Plains. Embedded within the primary objective are sub-objectives that focus on reducing the amount of summer fallow time and reversing the soil degradation that has occurred in the wheat-fallow cropping system. The experiment consists of four variables: 1) Climate regime; 2) Soils; 3) Management systems; and 4) Time. The climate variable is based on three levels of potential evapotranspiration (ET), which are represented by three sites in eastern Colorado. All sites have annual long-term precipitation averages of approximately 400,450 mm, but vary in growing season open pan evaporation from 1600 mm in the north to 1975 mm in the south. The soil variable is represented by a catenary sequence of soils at each site. Management systems, the third variable, differ in the amount of summer fallow time and emphasize increased crop diversity. All systems are managed with no-till techniques. The fourth variable is time, and the results presented in this paper are for the first 12 yr (3 cycles of the 4-yr system). Comparing yields of cropping systems that differ in cycle length and systems that contain fallow periods, when no crop is produced, is done with a technique called "annualisation". Yields are "annualised" by summing yields for all crops in the system and dividing by the total number of years in the system cycle. For example in a wheat-fallow system the wheat yield is divided by two because it takes 2 yr to produce one crop. Cropping system intensification increased annualised grain and crop residue yields by 75 to 100% compared to wheat-fallow. Net return to farmers increased by 25% to 45% compared to wheat-fallow. Intensified cropping systems increased soil organic C content by 875 and 1400 kg ha,1, respectively, after 12 yr compared to the wheat-fallow system. All cropping system effects were independent of climate and soil gradients, meaning that the potential for C sequestration exists in all combinations of climates and soils. Soil C gains were directly correlated to the amount of crop residue C returned to the soil. Improved macroaggregation was also associated with increases in the C content of the aggregates. Soil bulk density was reduced by 0.01g cm,3 for each 1000 kg ha,1 of residue addition over the 12-yr period, and each 1000 kg ha,1 of residue addition increased effective porosity by 0.3%. No-till practices have made it possible to increase cropping intensification beyond the traditional wheat-fallow system and in turn water-use efficiency has increased by 30% in West Central Great Plains agroecosystems. Cropping intensification has also provided positive feedbacks to soil productivity via the increased amounts of crop residue being returned to the soil. [source] The genetic and economic impact of the CIMMYT wheat breeding program on local producers in the Yaqui Valley, Sonora MexicoAGRICULTURAL ECONOMICS, Issue 5 2010Lawton L. Nalley CIMMYT; Public wheat breeding; Economic impact of technological change Abstract This article quantifies the productivity gain from CIMMYT-released semidwarf bread wheat (Triticum aestivum) cultivars over time, using test plot data from Mexico's Yaqui Valley. Previous studies have shown a deceleration in irrigated wheat yield growth since the 1980s, which could be due to slowing increase in genetic potential. Our results suggest that CIMMYT cultivars contributed a 0.46% annual increase (about 38 kg/ha annually) to wheat yields in the Yaqui Valley, which raised local wheat producers' revenue by an average of $4 million annually for the period 1990 to 2002, and by approximately $9 million in 2002. [source] | |||||||||||||