用FAO-56作物系数法推求控制灌溉条件下晚稻作物系数及验证

Estimation and verification of crop coefficient for water saving irrigation of late rice using the FAO-56 method

根据国家"863"节水农业重大专项试验资料,利用FAO-56推荐的分段单值法和双值法构建了控制灌溉条件下晚稻的作物系数曲线,分析了调整灌溉或降雨后的最大作物系数值对双值法水稻作物系数计算结果的影响,并根据2004年实测资料对研究结果进行了验证。结果表明:控制灌溉条件下,晚稻分蘖期、拔节孕穗期、抽穗开花期及乳熟期的作物系数实测值分别为1.14、1.49、1.43和1.12。分段单值法得到初始生长期、生育中期和后期的作物系数分别为1.1、1.39和0.79。降雨频繁阶段或灌溉阶段,对最大作物系数作调整后,减小了双值法作物系数计算值与实测值的误差。验证结果表明,2004年晚稻累积蒸发蒸腾量模拟值与实测值的相对误差为12.42%～16.24%,以基于调整后的双值法作物系数的晚稻蒸发蒸腾量模拟结果与实测值最为接近。

Crop coefficient curves for late rice were estimated using FAO-56 single and dual crop coefficient methods with experimental data from the ＂863＂ National Key Project on water-saving agriculture. Effects of adjusted maximum crop coefficient on dual crop coefficient were evaluated and the results of single and dual crop coefficient were tested by comparing the estimated and observed evapotranspiration in 2004. The rice crop coefficients at tilling, joint-booting, ear sprouting-flowering and milking stages under water saving irrigation conditions are 1.14, 1.49, 1.43 and 1.12, respectively. Estimated values obtained by FAO-56 single crop coefficient method are 1.1, 1.39 and 0.79 for the initial, development and last stages. The reestimated dual crop coefficient improved the precision of crop coefficient and reduced the relative error of crop evapotranspiration. Tested result showed that： relative error between the total crop evapotranspiration measured in 2004 and that estimated by using the single and dual crop coefficient varied within 12.42%-16.24%and dual crop coefficient method was the most suitable one for crop coefficient estimation.