中文摘要：

用分室根箱试验，研究了油菜-水稻轮作条件下红壤性水稻土根区与非根区土壤不同形态钾素含量变化特点。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，非根区内、中、外区土壤水溶性钾向根区迁移，交换性钾向水溶性钾转化，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，淹水促进了非根区水溶性钾向根区的扩散，交换性钾向水溶性钾的转化。随着水稻生长和吸钾强度增大，根区与非根区土壤交换性钾含量均显著降低。水稻季末期作物吸钾强度减小，根区土壤水溶性钾含量降低至一定程度时就不再减少，而非根区水溶性钾继续向根区扩散。整个轮作期，根区与非根区土壤非交换性钾含量与不种作物处理相比差异不显著。可见，作物首先吸收利用根区土壤钾，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，交换性钾和水溶性钾是红壤性水稻土主要供钾形态，作物吸收利用的非交换性钾较少。

英文摘要：

Dynamics of potassium in root-zone and non-root-zone red paddy soils under rapeseed-rice rotation was studied through a rhizobox equipment. Results showed that soil water soluble K and exchangeable K in root-zone soils were reduced first at the early stage of rapeseed growth. Along with plant growing and K uptake, 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 were moving towards to the root zone. Soil exchangeable K were transformed into water soluble K, thus decreasing gradually. In the early stage of rice growth, water-logging promoted diffusion of soil water soluble K from non-root zone to root zone and transformation of exchangeable K into water soluble K. Along with growth of rice plant and K uptake, soil exchangeable K in each part decreased significantly. In the late stage of rice growth, plant K uptake reduced in intensity. Soil water soluble K in the root zone dropped to a certain extent and then stopped declining, while soil water soluble K in the non-root zone kept on diffusing towards the root zone. During the whole rotation cycle, the treatment （with cropping） and CK （without cropping） were not much different in nonexchangeable K in the root zone and non-root zone. It revealed that the plant first absorbed K in the root zone, of which the K reserve was replenished with K gradually diffused from the non-root zone. The closer to the root zone, the greater the contribution to K uptake by plant. Within one rotation cycle, soil exchangeable K and water soluble K are the main forms of potassium available to the plant, and little nonexchangeable K could be absorbed.