SIMULATION ,BENCHMARKINGANDIMPROVEMENTOF SORGHUM YIELD AND WATER PRODUCTIVITY IN RAIN FED AGRICULTURE USING AQUACROP MODEL

Abstract

Due to the rapid growth in world population, the pressure on water resources to feed the growing population is increasing. The Nile water share of Sudan is almost exploited; and agricultural production by rained water is threatened by the pressure of climate change. It is inevitable that the production per unit water consumed, the water productivity, must be increased to meet this challenge. This research therefore ,focuses on the benchmarking of physical water productivity in rain fed areas and gaining a better understanding of the temporal and spatial variations and the scope for possible improvement. A review of the available records and sources that provide measurements of crop-water productivity was consulted to assess plausible ranges of water productivity levels for rain fed Sorghum crop and to provide a first explanation for the differences that are found using AQUACROP model. As such, this study may be considered as crucial step to establish a water productivity database for the rain fed Sorghum crop in the country. Sorghum (Sorghum bicolor (L.)Moench) which is the most important cereal crop in Sudan has been constrained by the detrimental effect of drought which has often caused food shortages. Almost 90% of the total sorghum cropped area is rain-fed, and 60% of that is in drought prone soil conditions. Spatial Sorghum (Sorghum bicolor (L.)Moench) which is the most important cereal crop in Sudan has been constrained by the detrimental effect of drought which has often caused food shortages. Almost 90% of the total sorghum cropped area is rain-fed, and 60% of that is in drought prone soil conditions. Spatial information on water use, crop production and water productivity will play a vital role for water managers to assess where scarce water resources are wasted and where in a given region the water productivity can be improved. Hence, a methodology has been developed in this study to quantify spatial variation of crop yield, evapotranspiration and water productivity using the AQUACROP model in five stations. The AQUACROP model is used to investigate optimum sowmg date that result in maximization of gram and biomass yield. Benchmarking of rain fed Sorghum actual and potential grain and biomass yield and water use efficiency in different agro-climate zones was made for the year 1979 to 2013. AQUACROP model was applied at five locations (Gedaref, Damazin, Dalang, El Fashir, and El Obeied) each representing an agro- climate zone. The high gap between measured and modeled water productivity showed that it is possible to introduce different means (water harvesting and improved cultural practices) to shorten this gap. Causes of poor yield performance were investigated and consequently measures needed to improve performance were identified.introduce different means (water harvesting and improved cultural practices) to shorten this gap. Causes of poor yield performance were investigated and consequently measures needed to improve performance were identified. The study indicates that increase in sorghum yields under historical climate conditions in the different studied stations is possible when early sowing is used and initial rain showers are utilized. Stations with high rain fall (Damazin, Gadaref and Dalang) show little variations in inter-annual yields but with a tendency towards high yields. The obtained WUE is lower in the driest regions (El Fashir, and El obyied) and higher for those of high rain fall. To aid decision makers and crop growers in rain fed areas a set of recommendations for policy making and for future research were identified.