长期施钾下中国3种典型农田土壤钾素固定及其影响因素研究

【目的】探索不同轮作方式和不同气候下，长期施钾对土壤钾素固定的影响。【方法】采用室内模拟法和X射线衍射分析技术研究了中国3种典型农田土壤，即灰漠土、潮土和紫色土在长期施钾条件下对外源钾固定能力的变化，并分析了影响土壤钾素固定的主要因素。【结果】在外源钾加入浓度0.4～4.0 g•L-1的范围内，长期施钾与不施钾相比，水云母含量较低的紫色土对外源钾的固定量和固定率显著降低，分别降低了91～559 mg•kg-1和14％～23％；水云母含量较丰富的潮土固钾量和固钾率略有降低，分别降低了35～274 mg•kg-1和6％～8％；而水云母含量丰富的灰漠土固钾能力没有发生明显变化。长期施钾对3种土壤SOC、CEC和<0.002 mm粘粒含量均无显著影响，而缓效钾和K+饱和度分别增加了11.3～349.9 mg•kg-1和11％～65％。【结论】长期施钾主要是通过影响土壤含钾矿物组成的变化，即水云母向云母-蒙脱石混层层间矿物的转化，而影响土壤钾素的固定，长期施钾延缓或阻止了这种转化，使土壤对外源钾的固定能力降低；土壤缓效钾含量和K+饱和度增加，也使土壤固钾能力降低。

Potassium Fixation and Affecting Factors of Three Typical Soils Under Long-Term Potassium Fertilization in China

【Objective】Effect of long-term potassium (K) fertilization on K fixation by soils under different cropping systems and climates was studied. 【Method】Samples taken from the NP and NPK treatments in three typical soils (viz., gray desert soil, fluvo-aquic soil and purple soil) were analysed for changes in K fixation and their affecting factors by the methods of simulating in laboratory and X-ray diffraction under long-term K fertilization. 【Result】When added K ranging from 0.4 to 4.0 g/L, the K fixation capacity and K fixation rate of purple soil in which hydromica content was low decreased significantly in NPK treatment, the decline value ranging from 91 to 559 mg/kg and 14% to 23％, while decreased slightly in fluvo-aquic soil in which hydromica content was abundant, the decline value ranging from 35 to 274 mg/kg and 6% to 8％, and remained unchanged in gray desert soil in which hydromica content was very abundant in the same treatment, compared with the NP treatment, respectively. The contents of SOC, CEC and <0.002 mm clay in tree soils remained unchanged under long-term K fertilization, while the slow available K content and K+ saturation increased ranging from 11.3 to 349.9 mg/kg and 11％ to 65％, respectively.【Conclusion】Long-term K fertilization arrested the transformation of hydromica into mixed-layered mica-smectite component and then K fixation capacity decreased. Besides, the increase of the slow available K content and K+ saturation induced the decrease of the K fixation capacity.