长期施用化肥和秸秆对紫色土非交换性钾释放特性研究
Study of the Effects of Long-Term Chemical Fertilization and Straw Returning on the Characteristics of Nonexchangeable Potassium Release in Purple Soil

土壤非交换性钾的释放总量和释放速率是土壤供钾能力的重要指标.本文采用CaCl₂连续提取的方法研究了22年长期不施肥(CK)、NP(不施钾肥)、NPK(施钾肥)、NPKS(钾肥与秸秆还田配施)和S(单施秸秆)对紫色土非交换性钾释放特性的影响，以期为紫色土钾素管理提供科学依据.结果表明：当运用不一样的施肥处理紫色土非交换性钾的释放全部是前期迅速释放、后期缓慢平稳释放的特点.采用4种动力学方程对紫色土交换性钾的释放过程进行模拟发现，前期快释放阶段(1~168 h)用Elovich方程(对数曲线方程)模拟最佳，释放量占全过程的74.2%~77.0%；后期慢释放阶段(168~1 472 h)用抛物线方程模拟效果最佳.不同处理土壤非交换性钾的释放速率和释放量的差异有统计学意义，其大小为：S＞原始土壤＞NPKS、CK＞NPK＞NP，长期不施钾肥的NP处理非交换性钾的释放速率比NPK处理低18.3%，比试验前土壤低26.7%；该处理土壤的非交换性钾累积释放量(133.32 mg/kg)仅占NPK释放量的78.69%；化肥配施秸秆土壤非交换性钾释放量为176.26 mg/kg，释放速率为16.13 mg/kg·h^-1略高于氮磷钾施肥，秸秆还田能够提高紫色土供钾能力.
The total release amount and release rate of soil nonexchangeable K are important parameters of the potassium supply capacity of the soil. In order to provide a scientific guidance for potassium management in purple soil, the release characteristics of nonexchangeable K in purple soil in a long-term (1991-2013) experiment were investigated, in which the CaCl₂ sequential extraction method was used and 5 fertilizer treatments were made: no fertilizer (CK), chemical NP fertilizer (NP), chemical NPK fertilizer (NPK), straw returning with chemical NPK fertilizer (NPKS), and straw returning only (S). The simulation experiment showed the release of nonexchangeable K in purple soil was characterized by a rapid release in the early period (1-168 h) and a slow and stable release in the later period (168-1 472 h) in all the treatments. Four kinds of kinetic equations were tested for their suitability to describe the release of non-exchangeable K. The result showed that the release of nonexchangeable K during the early period accounted for 74.15%-76.99% of the total with a high release rate of nonspecific adsorption K, while the release of specific adsorption K during the later period was slower in purple soil. Elovich models were the best to simulate the early period, but parabolic diffusion models were the best to simulate the later period. The amount of release and release rate of purple soil showed significant difference between the 5 treatments (S > original > NPKS, CK > NPK > NP). The rate of non-exchangeable K release in the treatment NP was 18.3% lower than in the treatment NPK and was 26.7% lower than the original soil while its accumulations of non-exchangeable K release (133.32 mg/kg) was 78.69% of NPK. The rate of non-exchangeable K release in the treatment NPKS was 176.26 mg/kg, and its rate was 16.13 mg/kg·h^-1, a little higher than in the treatment NPK, indicating that straw returning can improve the content of