保护性耕作对潮土物理性质的影响

为了研究保护性耕作对土壤物理性质的影响，以黄淮海平原典型潮土区小麦—玉米轮作系统的长期定位试验为基础，探讨不同耕作方式与秸秆还田处理下土壤容重、饱和导水率、紧实度、含水量的变化。结果表明，0~20 cm土层，土壤容重、土壤紧实度随着翻耕频率的减少而增加，每两年翻耕一次(CNTW2T)和每四年翻耕一次(CNTW4T)的土壤紧实度比长期免耕分别降低了40%、17%，土壤紧实度与土层深度呈显著正相关；保护性耕作改变土壤导水性能，随着免耕年限的增加，土壤饱和导水率显著降低；少免耕土壤含水量比传统翻耕高0.77%~3.01%。秸秆覆盖能显著降低土壤紧实度，改良土壤压实状况，提高土壤饱和导水率，减少土壤水分蒸发，从而改善土壤保水能力。免耕有利于土壤蓄水保墒，但长期免耕易导致土壤压实，不利于作物生长，少耕(CNTW2T、CNTW4T)既可改善土壤导水、保水性能，又可减少土壤压实，因此在黄淮海平原实施少耕与秸秆还田相结合的保护性耕作有利于改良土壤物理性质，提高土壤保水能力。

Effects of Conservation Tillage on Physical Properties of Fluvo-aquic Soil

To study the effects of conservation tillage on soil physical properties, a long-term field experiment was conducted on Huanghuaihai Plain in a winter wheat-summer maize rotation system. The soil bulk density, hydraulic conductivity, the degree of soil compactness and soil water content was studied under different tillage and crop retention. The results showed that, in the soil profile (0-20 cm), soil bulk density and the degree of soil compactness increased with the decreasing intensity of tillage, compared with long-term no-tillage the degree of soil compactness under tillage once every 2 years or 4 years (CNTW2T, CNTW4T) decreased 40%, 17% respectively, the degree of soil compactness showed a positive linear relationship with the soil depth; conservation tillage improved soil hydraulic conductivity function, soil hydraulic conductivity decreased significantly over time under no-tillage; soil water content under reduced and no-tillage were 0.77%-3.01% higher than conventional tillage. Covering crop mulch reduced soil compaction markedly, improved the compacted soil structure, increased soil hydraulic conductivity, reduced soil water evaporation, thereby, improved soil water-holding capacity. No-tillage had good effects on soil water retention, however, a long-term no-tillage leaded to soil compaction which had negative effects on crop growth. Reduced tillage (CNTW2T, CNTW4T) not only improved soil water infiltration and retention function, but also reduced soil compaction. Therefore, on Huanghuaihai Plain, the application of conservation tillage which consists of reduced tillage and crop retention can improve soil physical properties and enhance soil water conservation effect.