ارزیابی کارایی مدل آکواکراپ برای گیاه ذرت تحت مدیریت آب و کود (مطالعه موردی: شهرستان شوش)

امروزه بهینه‌سازی مصرف آب از اولویت‌های اصلی کشاورزی می‌باشد. چنانچه مدیریت آب در مزرعه بهبود یابد کارآیی مصرف آب نیز افزایش پیدا می کند. مدیریت آب در مزرعه را می‎توان با کمک مدل‌های شبیه‌سازی به‌صورت بهینه انجام داد. در این تحقیق کارآیی مدل aquacrop در پیش‌بینی عملکرد گیاه ذرت در شرایط مختلف مدیریت آب و کود مورد ارزیابی قرار گرفت. این تحقیق در قالب طرح کرت‌های خرد شده با تیمار اصلی کود اوره (شامل 100، 80 و50 درصد کود مورد نیاز گیاه ذرت (n0،n1 و n2)) و تیمار فرعی مقدار آب آبیاری (شامل آبیاری 100، 80 و50 درصد نیاز آبی‌گیاه (e0،e1 وe2)) با چهار تکرار اجرا شد. مطابق نتایج‌، مدل بیش‎ترین حساسیت را نسبت به دو پارامتر به زمان گل‎دهی و زمان پر شدن غلاف توسط دانه‎ها داشت. همچنین در واسنجی مدل برای شبیه‌سازی عملکرد ذرت، مقادیر بهره‌وری آب نرمال‌شده (wp) و ضریب رشد پوشش (cgc) به‌ترتیب برابر 31 (گرم بر مترمربع) و 24.2 درصد به‌دست آمدند. علاوه بر این مطابق نتایج این‌تحقیق، بهترین و ضعیف‌ترین شبیه‌سازی عملکرد ذرت به‌ترتیب مربوط به تیمارهای n0e1 و n2e0 بود. به‌طور کلی، مدل در تنش‌های کم‌آب و کود، شبیه‌سازی مناسبی داشت، به‌طوری‌که در برآورد میزان دقت شبیه‌سازی عملکرد (‌تیمار n0e1) مقادیر ce، rmse، d، me و crm به‎ترتیب برابر 0.2 ، 0.32، 0.73، 3.37 و 0.01 به‎دست آمد. در مجموع، مطابق نتایج این تحقیق، کارایی مدل aquacrop برای کشت ذرت دانه‌ای در منطقه‌ی شهرستان شوش مناسب ارزیابی شد و می‌توان از این مدل برای مدیریت آب در مزارع ذرت استفاده کرد.

evaluating the efficiency of aquacrop model for corn plant underwater and fertilizer management (case study: shush city)

introduction the ever expanding management needs have led to computer models play important role in modern agricultural management. the aqua crop model is one of these models, which is designed to simulate crop performance by the food and agriculture organization (fao), taken from the review articles of the journal of irrigation and drainage no. 33, prepared by dornbas and kasam (1979). was, expanded, and developed. among the specifications of the aqua crop model in comparison with similar models, we can mention its simplicity, high capability, and good accuracy. methodology this research was conducted in bilal village of shush city of khuzestan province in 2014. the climate of the region is hot and dry and the annual rainfall is about 250 mm. the main cultivation of this city is corn. regarding the importance of this product in the city of shush, we can be content with the fact that in 1394, it has been the first place in corn production in the province. this research is in the form of split plots with the main treatment of urea fertilizer (including 100, 80, and 50% of the fertilizer required for corn (n0, n1, and n2)) and sub treatment of irrigation water (including irrigation of 100, 80 and 50% of water requirement) with four replications. according to the results, the model had the highest sensitivity to the two parameters of flowering and seed pod filling periods. also, in model calibration to simulate corn yield, normalized water productivity (wp) and canopy growth coefficient (cgc) values of 31 (g / m2) and 24.2% were obtained, respectively.results and discussion flowering time and pod filling time were the most sensitive parameters of the model (with moderate high sensitivity). therefore, more care should be taken in measuring these parameters, because otherwise, the model simulation error may increase sharply. also, the model had no sensitivity to the time of germination of seeds. the statistical results show that the best simulation occurred in the n0e1 treatment with the least stress. as the stress increased, the simulation and observation values became more different. in treatments where 50% fertilizer stress was applied, the simulation values are very different from the observed values. simulation is not appropriate in these treatments and the aqua crop model has not been able to predict product performance under these stresses.conclusionsaccording to the results of this study, the best and weakest corn yield simulations were related to n0e1 and n2e0 treatments, respectively. the results also showed the accuracy of performance simulation in n0e1 treatment, based on ce, rmse, d, me, and crm statistical indices which are 0.2, 0.32, 0.73, 3.37, and 0.01 respectively, was higher than in other treatments. therefore, the aqua crop model has a more suitable simulation when water and fertilizer stresses are low. in general, according to the results of this study, the efficiency of the aqua crop model for grain corn cultivation in shush city was considered appropriate and this model can be used to manage water in corn fields.