ارزیابی مدل aquacrop برای شبیه‌سازی عملکرد ذرت و بهره‎وری آب تحت مدیریت مختلف کاربرد کود نیتروژن در کرج

مدل aquacrop از جمله مدل‌های گیاهی است که برای شبیه‌سازی عملکرد گیاهان زراعی تحت تنش‌های مختلف از جمله کود نیتروژن مورد استفاده قرار می‌گیرد. در این پژوهش به‌منظور شبیه‌سازی اثر مدیریت‌های مختلف کاربرد کود نیتروژن بر عملکرد گیاه ذرت از داده‌های برداشت شده در مزرعه 500 هکتاری موسسه تحقیقات اصلاح و تهیه نهال و بذر (کرج) استفاده شد. در این طرح کود نیتروژن در سه سطح (n1: 100 درصد، n2: 80 درصد و n3: 60 درصد توصیه کودی) و زمان تقسیط آن به دو روش (t1: سه تقسیط مساوی شامل مراحل 64 برگی، 10 برگی و تاسل‌دهی و t2: چهار تقسیط مساوی شامل مراحل 64 برگی، 10 برگی، تاسل‌دهی و تلقیح) در نظر گرفته شد. سپس همه تیمارها با تیمار شاهد که شامل کوددهی به‌صورت عرف در منطقه و به‌روش سنتی بود، مقایسه شدند. نتایج نشان داد که مدل aquacrop برای شبیه‌سازی عملکرد دانه ذرت دچار خطای بیش‌برآوردی (mbe>0) و برای شبیه‌سازی بهره‌وری آب دچار خطای کم‌برآوردی (mbe<0) شد. خطای مدل aquacrop برای شبیه‌سازی عملکرد در روش t1 حدود 0/36  تن در هکتار و در روش t2 حدود 0/24 تن در هکتار بود. بر اساس آماره nrmse، دقت این مدل برای شبیه‌سازی عملکرد در هر دو روش کوددهی در دسته عالی (nrmse<0/1) قرار داشت. خطای مدل aquacrop برای شبیه‌سازی بهره‌وری آب در روش t1 حدود 0/29 کیلوگرم بر مترمکعب و در روش t2 حدود 0/30 کیلوگرم بر مترمکعب بود. دقت مدل گیاهی aquacrop برای شبیه‌سازی بهره‌وری آب در هر دو روش کوددهی در دستة متوسط (nrmse<0/3) قرار گرفت. با توجه به‌ یافته‌های این پژوهش، دقت این مدل گیاهی برای شبیه‌سازی عملکرد بهتر از بهره‌وری آب بود و برای شرایط مشابه استفاده از آن پیشنهاد می‌شود.

evaluation of aquacrop model for corn simulation under different management of nitrogen fertilizer in karaj

introductionthe use of plant models is one of the methods that help researchers to understand the response of plants to different agricultural managements without conducting numerous experiments that require spending a lot of time and money. the use of plant models for simulating the reaction of plants to water deficit has a relatively long history and has gone through four stages: infancy, adolescence, youth and maturity. these models were introduced to researchers about fifty years ago by developing computer programs and taking into account the biochemical and biophysical mechanisms of solar energy available for the production of chemical energy and plant biomass. then, from the late 60s and with the advent of computers, the adolescent stage of plant modeling began. in the youth period of plant modeling, some beliefs of the previous years were lost and detailing and validation of models were considered. among the first measures taken to provide an acceptable model can be the results of research (1998) by gerik et al. cited. the results of these researchers’ studies led to the presentation of a model called sorkam, which was able to simulate the dynamic growth of sorghum (sorghum bicolor). the maturation period of plant modeling started in the 90s and has continued until now. during this period, more comprehensive software for the simulation of crop plants was developed by research centers around the world, including wofost, swap and mars and modeling the plant was widely used in different countries.the aquacrop plant model, which was developed by the food and agriculture organization since 2009, is one of the userfriendly, flexible and widely used models that is widely used by researchers due to the closeness of the simulation results to real conditions. the aquacrop model is used to simulate crops under various stresses, including fertilizer stress. in the developed version of the model, a semiquantitative method is used to simulate nitrogen fertilizer stress. however, this model has not been evaluated to simulate the effect of different amounts of nitrogen fertilizer under different application methods. for this reason, this issue is addressed in the present study. materials and methodsto achieve the research objective, the data was collected from the research project carried out in the 500hectare research farm of the seed and plant breeding research institute, located at 50.58° east longitude and 35.56° n latitude and 1312 m altitude. in this study, nitrogen fertilizer at three levels (n1: 100, n2: 80, and n3: 60) and application time in two methods (t1: three equal usage including 46 leaf stage, 10 leaf stage and reproduction stage, and t2: four equal usage including 46 leaf stage, 10 leaf stage, reproduction stage, and inoculation stage) were considered. then, all treatments were compared with the control, which included traditional fertilization applications in the region. the input data of the aquacrop model includes four groups of climatic, plant, soil and farm management data. climatic data includes maximum and minimum daily temperature, rainfall, reference plant evapotranspiration (et0) and annual average co2 concentration. soil data includes saturated hydraulic conductivity, soil texture and volumetric soil moisture at the points of crop capacity and permanent wilting. farm management data also includes farm management and fertility and irrigation. to evaluate the plant model, calibration was done first. for this purpose, the aquacrop model was evaluated based on the conditions without fertilizer stress and using the data collected from the farm in the first year. then, in order to calibrate this model under fertilizer stress conditions, it was necessary to determine the reduction coefficients of coverage development, maximum coverage, average reduction and normalized water productivity reduction percentage.