simulation of rice water productivity via cropsyst model under low irrigation and nitrogen fertilizer

introduction water consumption improvement in agriculture is very important compare with other sections. because of existing complexity in production and exploitation processes and optimized application of irrigation water and nitrogen especially in dry and semi-dry areas facing with water constraint is an important goal in this field. yield gap analysis can help to identify how much yield increase can be expected without examine the actual nutrient and water limitations. application of crop growth models is one of those effective methods to reach these goals. cropsyst is a simulation model for a variety of crops such as rice to enable us through calculations of data statistics regarding situation of water, weather, soil, management system, and plant genetic to get the correct results. cropsyst has been developed during the last 15 years into a multi-crop, multi-year simulation model and can connect to gis software consisting programs of cropsyst cultivation simulator system, reconstruction of meteorological data (climgen), gis connection program (arccs), watershed model, and several other useful programs. materials and methods in order to evaluate the effect of nitrogen fertilizer and irrigation on growth and yield of rice this study was conducted at the rice research institute of iran, located in rasht. to simulate the response function a split plot experiment as a randomized complete block design with three replications was conducted with three irrigation treatments (continuous, around 5and 8 days) as the main factor and the amount of nitrogen in four levels (0, 90, 120 and150kg n ha-1 source of urea) as sub-factor. version 3 of cropsyst was used in this study.to run the model four sets of data are required as input, including files location, soil, and plant management. definition, application and all the required parameters of the model and parameter ranges is stated in the model manual. results and discussion the model validations were based on the comparison between simulated and observed data for all treatments other than those used in model calibration. results of the evaluation showed that cropsyst model with regard to rmsen 7, 15 percent and r2 0.73, 0. 84 to simulate the yield seed rice and also with regard to rmsen 9, 10 percent accuracy of simulations appropriate.the results of the simulation based on the amount of transpiration water productivity for both years showed that i3n2 and i3n3 treatments had the highest amount. the results showed to simulated based on the amount of water and rain water productivity for both years showed that treatmenti3n4 and i3n3 had the highest amount. the amount of evaporation in irrigation water management two-year periodonly39% of evapotranspiration is evaporated, while the amount of intermittent irrigation management 5 and 8days, respectively, 35% and 32% respectively. the nitrogen fertilizer management control, 90, 120, 150kg ha, respectively, 39%and 34%, 35% and 32% of the evapotranspiration just evaporates. conclusions in the present study, the cropsyst model was calibrated, validated, and used as a tool to estimate climatically-driven potential yield, yield production and water balance components of rice under a range of n fertilizer and water regimes in a humid region of iran. cropsyst can be applied for simulation the effect of n and water management on growth, yield and water productivity of wheat under iranian subtropical conditions.