ارزيابي مدل گياهي CropSyst در شبيه سازي اثر توامان آب و نيتروژن بر عملكرد و بهره وري آب گندم

Evaluation of CropSyst model for water-nitrogen interactions in wheat yield and water productivity

Optimal water and nitrogen use is an important approach in arid and semi-arid regions. Crop simulation models may be used for studying cropping systems and optimizing these variables. The present study was carried out with the main objective of validation and performance evaluation of the detailed CropSyst model under varying N levels and water regimes. Its potential as N and water management tool was evaluated based on a field experiment in an arid irrigated ecosystem. The field experiment was carried out in a randomized complete block design with four replicates. There were four levels of applied water and three levels of N application as treatrttents in the proposed plots. The predicted grain yields had a good agreement compare to the observed data with RMSE of 0.41, 0.33, and 0.34 t ha"1 for the three growing seasons. The prediction of biomass was also satisfactory with significant R2 (>0.8) and Wilmotʹs index (0.9) values. The comparison of observed and predicted water productivity values showed that the estimations have more difference in the deficit irrigation regimes. The results indicated that the maximum water productivity value is related to the full irrigation and N application 120% of crop nitrogen demand and minimum water productivity value was occurred in applied water with a 120% of crop water demand and N application 60% of crop nitrogen demand. Consequently, when limited supplemental irrigation is combined with N fertilizer appropriate management, wheat water productivity can be substantially and consistently increased. The findings demonstrated that CropSyst model is an appropriate tool in predicting growth and yield of wheat under different N and irrigation application situations in this study and may thus be applied as a comprehensive and practical decision-making tool with the aim of improving wheat water productivity.