水田土壤非代换性钾的释放研究

The Study on Nonexchangeable K Release from Paddy Soil

通过盆栽耗竭试验并采用化学提取法和离子交换树脂法研究了稻田土壤各种形态钾的相互关系,非代换性钾的释放对水稻生长的影响,非代换性钾的测试方法比较以及非代换性钾释放与土壤固钾能力的关系。结果表明:土壤水溶性钾与CaCl_2、NH_4Cl浸提钾量间相关性良好,而非代换性钾与水溶性钾及CaCl_2、NH_4Cl浸提钾没有明显相关性。两季水稻植株从土壤中的吸钾量大部分来自水溶性钾和土粒表面电荷吸附钾,来自非代换性钾的部分占6.7％～43.2％,它取决于矿物种类和土壤质地,非代换性钾含量高,粘粒含量高且固钾率低的土壤,非代换性钾的释放量也高,非代换性钾含量高但固钾率也高的土壤,钾的释放受抑制。随着耗竭种植,非代换性钾的有效性越来越明显,它与植株吸钾的相关系数(Υ值)随着种植季数增加呈上升趋势,而水溶性钾、代换性钾与植株吸钾的相关性下降。离子交换树脂法可动态地反映非代换性钾的释放,过程分三个阶段,第一阶段为晶格边缘吸附钾的快速释放阶段;第二阶段为晶格层间钾向层外扩散的稳定速率阶段;当层间钾下降到一定程度后护散速率下降,最后趋于停止,此为第三阶段。树脂法与酸提取法呈良好相关,树脂法短期培养的测定结果能更好地反映非代换性钾对植株的有效性。

The relationship between different K forms in paddy soil, the effect of nonexchangeable K release on rice growth,the comparison of different methods for nenexchangeable K measurements and the correlation between nonexchangeable K release and the capacity of soil K fixation were investigated by pot exhausive cropping, chemical extraction and H+- saturated resin methods. The results indicated that there was good positive relationship between water soluble K and CaCl2,NH4Cl extractable K, while there was no evident correlation between nonexchangeable K and water soluble K as well as exchangeable K. The K uptake by plants in two harvests most came from water soluble K and was adsorbed by soil surface;the portion from nonexchangeable K only occupied 6. 7%-43. 2%, depending on soil mineral types and soil texture. The soil with high level of nonexchangeable K,high clay content and low capacity of soil K fixation could release more K, whereas in the soil with high level of exchangeable K and high capacity of soil K fixation,soil K release was inhibited to a certain extent. The availability of soil nonexchangeable K was increasing with exhausive cropping, and the correlation coefficient ( r ) between K uptake by plant and nonexchangeable K release was also increasing with exhausive cropping, meanwhile correlation coefficient (r) between K uptake by plant and water soluble K as well as exchangeable K was decreasing. The method using H+ - saturated resin could be used for showing K release from nonexchangable K dynamically, and the process can be divided into 3 stages, in the first stage, the K adsorbed by edge of soil particles released rapidly; in the second stage,the K between interlayer diffuse outside layer, the diffusion rate was stable;when K between interlayer decreased to a cretain point, the diffusion rate declined, that led to the third stage. There was good correlation between resin method and acid extraction method, the determination in short lime incubation by resin method could reflect availability of nonexchangeable K more accurately.