有限供水条件下玉米灌水时间确定方法的研究

Methods to Determine the Timing of Maize Irrigation When Irrigation Amount is Restricted

【目的】充分发挥自然降水的生产力,最大限度提高有限灌溉水资源利用效率,研究灌溉预报中确定灌水时间的方法。【方法】基于作物生长模型和土壤水热动态模拟模型,建立了玉米产量与水分关系模型,利用山西省文峪河试验站2017—2020年玉米生长季试验资料,通过最小二乘法确定了模型参数。并利用该站1957—2018年气象资料以灌溉需水量从小到大的顺序做频率分析,确定了5个典型年(分别对应5%、25%、50%、75%和95%这5个频率);针对不同的灌水定额(45、75 mm和105 mm)和灌水次数(1、2、3、4次和5次)组合,优化确定了相应的灌水时间,以累计有效降水量为自变量,以考虑可供水量修正的累计蒸散量为因变量,分析构建了相邻2次灌水期间累计蒸散量和累计有效降水量的关系,基于该关系提出了确定灌水时间的K-M法;在此基础上,利用2009—2018年的气象资料,通过模拟分析比较了3种方法(K-M法、动态灌水下限法和经验灌水法)的增产效益。【结果】结果表明,不同灌水定额下,累计蒸散量和累计有效降水量关系的相关系数均能达到0.92以上,表明该模型在年际间和不同灌水定额之间均有较好的适用性;随着灌水定额的增大,K-M法中参数M呈增大的趋势,表明参数M一定程度上具有灌水定额的物理特性。【结论】基于产量、效益和用水效率3方面对3种确定灌水时间方法的评价表明,与经验灌水法相比,以K-M法最好,动态灌水下限法次之。

【Objective】To reverse the continued decline of dwindling water resources in northern China, most regions have proposed to restrict groundwater extraction for irrigation. Optimizing irrigation timing and making most of natural precipitation and irrigation water is essential to minimizing crop yield loss due to the reduced irrigation amount. The purpose of this paper is to study the optimization of timing of maize irrigation. 【Method】Models relating maize yield and water usage were established based on crop growth model and soil water-heat coupling model. The model parameters were determined based on data measured from 2017—2020 from a maize field at Wenyuhe Experiment Station in Shanxi province. Meteorological data measured from 1957—2018 at the station was used in the frequency analysis for determining the irrigation amount by dividing the frequency from 5%to 95%. We optimized the timing of the irrigation assuming that the irrigation amount varied from 45 to 105 mm, and the times of irrigation varied from 1 to 5. The K-M model was used to determine the relationship between cumulative evapotranspiration and cumulative precipitation between two adjacent irrigations. Using the meteorological data measured from 2009 to 2018, the model was applied to optimize the irrigation timing, from which we compared the yield-increasing benefits obtained from the K-M method, the dynamic irrigation water limit method, and the empirical irrigation method. 【Result】The correlation coefficient between the cumulative evapotranspiration and the cumulative effective precipitation under different irrigation amount was greater than 0.92.With the increase in irrigation amount, the parameter M in the K-M method, which characterizes the irrigation amount, increased. 【Conclusion】Evaluation of the three methods for determining the optimal irrigation timing based on yield, benefit and water use efficiency showed that, compared with the empirical irrigation method, the K-M method was the best, followed by the dynamic irrigation water limit method.