反求根系吸磷速率方法的检验及其在苗期冬小麦土柱实验中的应用

VALIDATION OF THE INVERSE METHOD FOR ESTIMATING AVERAGE ROOTPHOS PHORUS-UPTAKE RATE AND ITS APPLICATION TO SOIL COLUMN EXPERIMENT WITH WINTER WHEAT SEEDLINGS

作物根系吸磷研究对于施肥管理和农业非点源污染控制有十分重要的意义。由于土壤剖面各深度处的根系吸磷速率尚无法直接测定,反求方法已成为估算其分布的主要手段之一。土壤剖面水溶性磷浓度实测空间步长SI、时间步长T以及水溶性磷浓度测量误差εpa是影响根系吸磷速率反求方法的几个主要因子。本文通过数值实验,首先探讨了SI、T和εpa不同取值对根系吸磷平均速率反求方法准确性和稳定性的影响。结果表明:当(a)土壤0～30 cm区域内实测空间步长SI取5 cm,30 cm以下取10～20 cm;(b)测量时间步长T介于5～20 d之间;(c)水溶性磷浓度测量的相对误差控制在15%以内时,根系吸磷平均速率估算值与理论分布之间的总体相对误差均在10%以内。在此基础上,应用该反求方法对土柱实验中冬小麦(苗期)根系吸磷平均速率分布进行了模拟估算,所得冬小麦各生长阶段吸磷总量的估算值与实测值吻合较好,两者间的相对误差均在10%以内。

Root-phosphorus-uptake（RPU） is a very important parameter for farmland fertilizer management and non-point source pollution control.Since it is almost impossible to determine RPU rate distribution in soil profile directly,it is often estimated using an inverse method,which,however,is influenced by factors,such as the spatial interval（SI） of soil soluble phosphorus（P） concentration measurements,the time interval（T） between the two successive measurements,and the measurement errors（εpa） of soil soluble P concentration,etc.In this study,several numerical simulation experiments were first conducted to explore effect of SI,T and εpa on accuracy and stability of the method.Results show that the overall relative error between the estimated and the theoretical average root-phosphorus-uptake rate distributions was less than 10% when（a） SI was set as 5 cm within the 0～30 cm soil layer and 10～20 cm in soil layers beyond 30 cm in depth;（b） T was set between 5 d and 20 d;and（c） εpa was controlled no more than 15%.On such a basis,the inverse method was applied to estimating average root-phosphorus-uptake rate distribution of winter wheat at the seedling stage in a soil column experiment.The estimated total P uptakes by winter wheat at various growth stages matched well with the measured values,with all the relative errors ranging within 10%.