土壤非交换性钾释放动力学特征及其生物

采用生物耗竭法和0.2mol L-1的NaTPB化学浸提法，利用不同动力学方程对我国8种主要土壤非交换性钾的释钾特性及其生物有效性进行定量评估。结果表明，供试土壤非交换性钾释放分为快速释放和稳定释放两个阶段，一级动力学方程、Elovich 方程、双常数曲线方程和抛物线扩散方程均能描述土壤非交换性钾的释放过程。根据双常数方程中的参数（a）所表征的土壤非交换性钾释放速率常数，供试8种土壤的释钾能力按取土地区存在着自西向东、自北向南渐减的趋势。盆栽试验中，在累积释钾量高且释放速率快的土壤上，黑麦草累积生物量、累积吸钾量和相对含钾量较高，表现出强的供钾能力；与此相反，累积释放量低且释放速率慢的土壤上，黑麦草各项指标偏低，供钾能力较弱。以黑麦草钾素丰缺临界值34.00 mg kg-1 DW-1和土壤非交换性钾释放速率396.32 mg kg-1 h-1作为评价指标，供试8种土壤中，仅取自新疆石河子、陕西常武和黑龙江哈尔滨地区的土壤在短期不施用钾肥的情况下能保证黑麦草丰产且不出现缺钾症状。因此，为了维持土壤钾素平衡和保证作物高产稳产，在我国西北、东北地区耕地土壤中应加强秸秆的循环利用，而在华中和华东地区则需增施钾肥和有机肥。

Release kinetics and bioavailability of nonexchangeable potassium in soil

Release characteristics and plant availability of nonexchangeable potassium (NEK) of 8 soils in China were investigated by using pot experiments, 0.2 mol L-1 NaTPB and different kinetic equations. The results showed that the kinetics of NEK release from soils consisted of two phases and was best described by first-order, Elovich, power and parabolic models. Rate constants which derived from the power function equations indicated that, the NEK release ability showed a general tendency of decrease from west to east and from north to south region in China. Ryegrass were grown for 8 harvests in pot experiments to evaluate K supplying capacity of the 8 soils. It found that the kinetics parameters obtained from the kinetics study can be used to well characterize the K supplying capacity. The values of cumulative dry matter (DM), cumulative K uptake and relative K concentration of ryegrass were higher in soils with higher NEK release amount and rate; on the contrary, they were lower in soils with lower NEK release amount and rate. The leaf K concentration of 34.00 g kg-1 DM-1 and NEK release rate of 396.32 mg kg-1 h-1 was obtained as a critical level to obtain 90% relative DM yield of ryegrass in the study. According to this critical value, the ryegrass grown on the soils come from Shihezi in Xinjiang, Changwu in Shanxi and Harbin in Heilongjiang without K application, could guarantee good yield and showed no potassium deficiency symptoms in a short incubation period. This finding implicated that, in order to maintain soil K balance and guarantee crop yield, crop straw would return to arable soil in west northern and east northern of China. However, K fertilizer and farmyard manure would increase applied in central and east region of China.