CALIBRATION OF THE CROPWAT MODEL FOR THE STUDY OF SOYBEAN PRODUCTION SYSTEMS

ABSTRACT CROPWAT is a model that uses water balance to study the water factor and productivity in production systems. In this sense, this study aimed to calibrate the CROPWAT for modeling rainfed and irrigated soybean production systems. Climate and soil data from a soybean-producing region in the south of Mato Grosso do Sul, Brazil, were used to implementing simulations in nine agricultural years, and crop shortfalls were calculated and compared with reference data. Statistical indices were applied to evaluate the performance of the model in its calibration. For validation, two field trials with 12 cultivars were implemented under irrigation and rainfed and the mean productivity in each water management was compared with the CROPWAT estimate by Student’s t-test. Accuracy (r) was 0.976 (“very strong”), precision (r2) was equivalent to 95.3%, and the indices of agreement (d) and performance (c) were considered excellent (0.95 and 0.93, respectively) in the calibration. Validation demonstrated that the hypothesis that CROPWAT correctly estimated soybean productivity under irrigated and rainfed systems cannot be rejected at 1 or 5% significance levels.

摘要：CROPWAT是一款基于水量平衡原理，用于探究生产系统中水分因子与作物生产力的模型。本研究旨在针对雨养与灌溉大豆生产系统的建模需求，对CROPWAT模型进行校准。研究采用巴西南马托格罗索州南部大豆主产区的气候与土壤数据，开展了9个农业年度的模拟试验，计算作物水分亏缺状况并与参考数据进行对比。通过统计指标对模型校准后的性能展开评估。验证环节设置了2组田间试验，分别在灌溉与雨养条件下种植12个大豆品种，采用Student t检验将两种水分管理模式下的实测平均生产力与CROPWAT模型的估算结果进行对比。校准结果显示，相关系数（r）达0.976，属于“极强相关”；决定系数（r²）为95.3%，拟合精度优异；一致性指数（d）与性能指数（c）分别为0.95与0.93，均达到优秀水平。验证结果表明，在1%或5%的显著性水平下，无法拒绝“CROPWAT可准确估算灌溉与雨养大豆生产系统生产力”的假设。