soil water balance and crop yield of winter wheat using aquacrop simulation model

the greatest limitations to agricultural development and production in iran are scarcity of water resources, ineffective irrigation scheduling and wasteful water usage. avenues discussed for optimum water use include improving water productivity by improving irrigation scheduling, farm water management and water profitability. the present study evaluated current water use and ways to improve winter wheat productivity by varying field scale water usage in the abshar irrigation network in esfahan province, iran. optimal irrigation depth and scheduling, and yield function for winter wheat using current water management tactics were determined. the availability of water, rotational water rights laws and field data were combined using the aquacrop simulation model for field scale crop growth. crop yield and winter wheat productivity were then simulated and compared to field results. field research indicated that 800 mm of water is applied annually for winter wheat and crop yield averages 5000 kg per hectare. improvements in water management and productivity based on different irrigation schedules (changes in depth and time) and water quantity schemes and the effect on water balance and crop yield were investigated. the baseline scheme used current conditions as a reference for other schemes. the results showed that eliminating the second, third and seventh irrigations from the schedule decreased the quantity of water applied by 38%r and yield by 4%, which produced a 45% increase in water productivity over the baseline scheme. however, improving agronomic management and decreasing the first irrigation depth by 50% (from 200 to 100 mm) also produced a slight variation in crop yield. increasing the water applied to the optimal depth increased water productivity, but increasing the water applied to greater than optimal levels had no significant effect on yield and decreased water productivity. the results showed that proper irrigation scheduling using the aquacrop model in combination with improved agronomic management decreased the quantity of water applied during irrigation 38%, increased crop yield by 16% and water productivity by 79%.