基于EPIC模型的四川丘陵区黑麦草生长过程及其土壤水分动态变化模拟

摘要

The definition of soil moisture dynamics is very important to improve the management of ryegrass pasture.The use of the environmental policy integrated climate (EPIC) model can improve the accuracy of cropping system simulations,thereby providing better information for decision making.In this study,field experiments and computer simulations were used to analyze the growth process of ryegrass and the dynamics of soil moisture in ryegrass pastures.Then,the accuracy of the EPIC model to simulate ryegrass growth and soil moisture was evaluated.The results showed that available soil water in the deep soil layer (0.4-0.6 m) was relatively lower from March to May,but increased from May to October.Appropriate nitrogen fertilization (75-225 kg/ha) significantly increased the forage yield and leaf area index of ryegrass pastures in the hilly region of Sichuan Province.The correlation index values between observed and simulated available soil water in the 0-1 m soil layer ranged from 0.86 to 0.95 with RRMSE values ranging from 6.0％ to 17.2％.The range of correlation index values between observed and simulated soil water in the 0-1 m soil layer was 0.57-0.92,and most values were ＞0.85.The correlation index values between simulated and observed values of forage yield,leaf area index,and hcight of ryegrass were ＞0.90,and there were no significant differences between simulated and observed values.In conclusion,the EPIC model can simulate soil moisture and forage yields of ryegrass pastures.These simulations can be used to evaluate the suitability of grain-forage cropping systems for the hilly regions of Sichuan Province.%明确黑麦草田土壤水分变化规律,对提高四川丘陵区人工草地管理水平具有重要的现实意义;校验EPIC模型,有利于改进并提高模型对黑麦草的模拟精度,对推进作物生产系统模拟与决策技术在草粮轮作系统的应用具有重要的实践意义.本研究通过田间试验与计算机模型相结合的方法,研究了四川丘陵区黑麦草生长过程及其土壤水分动态变化规律,明确了EPIC模型对黑麦草生长过程及土壤水分变化规律的模拟精度.结果表明,1)四川丘陵区黑麦草田土壤有效含水量在3-5月较低,深层(0.4～0.6 m)土壤水分在5-10月间可以得到较好恢复,适当增加氮肥投入,可以显著提高黑麦草最大叶面积系数和饲草产量,在刈割4茬的条件下,氮肥施入量不宜低于75kg/hm2,且不高于225 kg/hm2;2)黑麦草田0～1 m土层土壤有效含水量模拟值和观测值间的r值为0.86～0.95,RRMSE值为6.0％～17.2％,土壤水分剖面分布动态变化的模拟值和观测值间的r值介于0.57与0.92之间,且大部分大于0.85;3)EPIC模型模拟的黑麦草叶面积系数和株高与观测值间的r值均大于0.90,在统计范围内模拟值和观测值间差异不显著;黑麦草产量模拟值和观测值间的r值大于0.90,ME值和R2间差异小于0.02.总体而言,EPIC模型能够较好地模拟黑麦草生长过程,对黑麦草田土壤水分动态变化规律模拟较为准确,可以用来评价四川丘陵区以黑麦草为主的草粮轮作系统对当地气候条件的适应性.