长期浅耕与秸秆还田对关中平原冬小麦-夏玉米轮作土壤钾素含量及层化比率的影响

采用土壤分层采样和钾素化学形态分组方法，探讨连续13年秸秆全量还田与浅耕对关中平原冬小麦 夏玉米轮作体系土壤各形态钾素含量及层化比率的影响. 结果表明： 采样区土壤速效钾和非交换性钾均有显著的表聚现象和层化效应，速效钾及其组分表现尤为突出，且15～30 cm土层亏缺严重，已低于缺钾临界值；速效钾及其组分的土壤表层(0～5 cm)与5～15 cm和15～30 cm耕层土壤的比值(SR₁与SR₂)之间呈显著性差异，非交换性钾与矿物钾的比值则差异不显著. 连续秸秆全量还田对维持冬小麦 夏玉米轮作体系土壤钾库平衡有积极贡献，但应高度关注有效钾素表聚和层化对土壤钾肥力的负面效应.

Effect of long-term shallow tillage and straw returning on soil potassium content and stratification ratio in winter wheat/summer maize rotation system in Guanzhong Plain,Northwest China.

Soil stratified sampling method and potassium chemical fractionation analysis were used to investigate effects of long-term shallow tillage and straw returning on soil K contents and stra tification ratios in winter wheat/summer maize rotation system in Guanzhong Plain of Northwest China. The results showed that after 13-year continuous shallow tillage and straw returning, surface accumulation and stratification effect obviously occurred for soil available K (SAK) and non exchangeable K (NEK), which was particularly remarkable for SAK and its fractions. Serious depletion of SAK occurred in 15-30 cm soil layer, and the SAK value was lower than the critical va lue of soil potassium deficiency. Meanwhile, significant differences were found between SR₁ and SR₂ values of SAK and its fractions, SR was obtained by values of topsoil layer (0-5 cm) divided by corresponding values of lower soil layers (5-15 cm layer, SR₁, or 15-30 cm layer, SR₂). How ever, no significant difference was observed between SR values of NEK and mineral K. In conclusion, returning of all straw over 10 years in the winter wheat/summer maize rotation system contri buted greatly to maintaining soil K pool balance, while special attention should be paid to the negative effects of surface accumulation and stratification of SAK on soil K fertility.