旱地轮作对西藏中部土壤恢复过程的影响

Effect of Rotations on Degradation and Recovery of Dryland Soils in Central Tibet

于西藏中部生态条件下,就麦类作物轮作、麦油轮作对土壤化学和生物性质的影响以及农田养分平衡等进行了初步研究.结果表明,不同轮作方式对土壤化学和生物学过程具有显著不同的影响.轮作周期内春青稞→春油菜、春小麦→春油菜轮作对以细菌为主导的土壤微生物的生长与繁殖具有显著的促进作用,耕层土壤有机质、全氮、全磷的绝对增长量分别达3.05～3.06 g/kg,0.06～0.07 g/kg,0.01～0.26 g/kg.麦类作物间,春小麦→春青稞轮作对土壤肥力亦具明显的恢复作用;春小麦→春小麦连作、春青稞→冬小麦轮作土壤微生物区系构成不甚协调,土壤细菌数量明显较低,0～30,31～60 cm土层有机质、全氮、全磷总体呈不同程度的退化趋势.在较高外源钾投入条件下,不同轮作方式的土壤钾素均呈不同程度的亏缺状态.

Field experiments were carried out to determine effects of cereal-cereal or wheat-oilseed rotation on degradation, recovery and nutrient balance of dryland soils. Results showed that soil biomass dominated with bacteria was increased significantly by spring highland barley-spring oilseed or spring wheat-spring oilseed. The increments of organic matter, total nitrogen and total phosphorus in soil were 3.05 - 3.06 g/kg, 0.06 - 0.07 g/kg and 0.01-0.26 g/kg, respectively. Spring wheat-spring highland barley or spring highland barley-winter wheat rotation also was benefited to raise soil fertility. However, spring wheat continuous cropping and spring highland barley-winter wheat rotation had a positive effect on micro-organism community in soil where the amount of soil bacteria decreases significantly. There was a degradation trend for the organic matter, total N and total P in 0-30 cm, 31-61 cm soil layers. Although K was input in soil, there was a deficiency of soil K in different rotation systems.