水旱轮作下根区与非根区黄褐土钾素动态研究

Potassium dynamics in root-zone and non root-zone in yellow cinnamon soil with paddy-upland rotation

采用分室根箱试验,研究了油菜—水稻轮作条件下黄褐土根区与非根区土壤钾素动态变化特征,以期为土壤供钾机制研究及合理的根际养分调控提供依据。结果表明,轮作前季(油菜季)前期,根区土壤水溶性钾和交换性钾首先出现相对亏缺;随着油菜生长和吸钾强度的增大,根区非交换性钾含量也显著降低,非根区内、中、外区土壤水溶性钾向根区迁移,交换钾和非交换钾向水溶钾转化,含量均逐渐降低,且距根区越近,降低幅度越大。轮作后季(水稻季)前期,淹水促进了水溶性钾向根区的扩散,非根区外区水溶钾和交换性钾含量明显降低;随着水稻生长和吸钾强度增大,根区与非根区土壤水溶钾和交换性钾含量降低至一定程度时就不再减少,而非交换性钾显著降低。说明作物吸收的钾主要来自于根区,并由非根区钾逐渐向根区迁移,距根区越近,对作物吸钾量的贡献越大。在一个轮作期内,非交换性钾是黄褐土主要供钾形态,其次是交换性钾和水溶性钾。

Potassium dynamics in the root-zone and the non root-zone in yellow cinnamon soil with a rapeseed-rice rotation system was studied through a rhizobox device to provide evidence for research on soil K supplying mechanism and reasonable control of rhizosphere nutrition. The results show that soil water soluble K and exchangeable K in the root-zone are reduced at early stage of rapeseed growth under the rapeseed-rice rotation. Along with rapeseed growth and K uptake, soil non-exchangeable K in the root-zone are also decreased significantly. Soil water soluble K in the inner （0-20 mm）, middle （20-40 mm） and outer （40-60 mm） parts of the non root-zone are moved forward to the root-zone. Soil exchangeable K and non-exchangeable K are transformed to water soluble K and decreased gradually. In the early stage of rice growth, water-log cultivating practice promotes the diffusion of soil water soluble K from the non root-zone to the rootzone and transition of exchangeable K to water soluble K. Along with the growth of rice and more K uptake, soil non-exchangeable K in each part is decreased significantly, while soil water soluble K and exchangeable K are not decreased. These results indicate that K uptake by crops is mainly contributed by the root-zone, and K in the non root-zone can be moved to the root zone gradually depending on the distance. Within the rotation system, soil non-exchangeable K is the main potassium source, followed by soil exchangeable K and water soluble K.