稻-油轮作下保护性耕作对土壤肥力的影响及评价

本文选取湖北省武穴市、荆州市和武汉市3个稻-油轮作长期定位试验点(试验时间分别为9年、5年和3年),通过连续监测土壤容重、孔隙度、p H、有机质、全氮、全钾、碱解氮、速效磷和速效钾等,研究在不同耕作年限和方式下,秸秆还田和免耕对水稻季(2015年10月)和油菜季(2016年5月)各土层(0~20 cm和20~40 cm)中土壤物理性质和养分的影响,并应用内梅罗指数法综合评价各土层土壤肥力水平,以探讨长期秸秆还田对土壤肥力的影响。结果表明:1)秸秆还田处理使水稻季和油菜季的土壤容重降低2.00%~16.54%,土壤总孔隙度增加1.00%~15.07%;而免耕处理下油菜季的变化与其相反,水稻季的变化不显著。2)秸秆还田处理增加了3个试验点0~20 cm土层中有机质(4.76%~35.07%)、全氮(1.80%~32.03%)、速效磷(20.95%~65.82%)、碱解氮(5.97%~37.00%)和速效钾(8.71%~133.04%)的含量,其中速效钾含量的增加幅度最高;免耕处理对土壤各养分的影响不显著,而在配施秸秆后,相对于其他处理,其对各养分的增加效果相对最好。各处理对20~40cm土层的影响与0~20 cm土层相似,但整体增加效果没有后者显著。3)各试验处理中,免耕+秸秆还田和施氮磷钾肥+秸秆还田两种处理增加各土层土壤综合肥力系数较大(7.56%~25.93%),它们对土壤肥力的提高效果相对较好。

Effect of conservation tillage on soil fertility under rice-rape rotation system

In this study, the long-term effects of straw returning and no-tillage on physical properties and nutrient content of soils were assessed by continuous monitoring of soil bulk density, porosity, pH, organic matter, total nitrogen, total potassium, available nitrogen, available phosphorus and available potassium. The study considered different soil layers (0-20 cm and 20-40 cm) under rice-rape rotation system in Wuxue, Jingzhou and Wuhan Cities in Hubei Province for various farming years (9, 5 and 3 years) and cultivation systems. Also the Nemoro index method was used to evaluate soil fertility in different soil layers. The aim of the study was to provide the scientific basis for application of conservation tillage measures and optimization of field management. Results showed that:1) straw returning reduced soil bulk density by 2.00%-16.54% and increased total porosity by 1.00%-15.07% in rice and rape seasons. The changes in rape season were reversed under no-tillage treatment, while no significant changes were noted in the rice season. 2) Straw returning treatment increased the contents of organic matter (4.76%-35.07%), total nitrogen (1.80%-32.03%), available phosphorus (20.95%-65.82%), available nitrogen (5.97%-37.00%) and available potassium (8.71%-133.04%) in the 0-20 cm soil layer across the three sites. Compared with other nutrients, the greatest increase was recorded in available potassium. No significant differences were observed in no-tillage, although it had the best effect in terms of increase in soil nutrients compared with the other treatments after straw returning. The effect of each treatment on the 20-40 cm soil layer was similar to that on the 0-20 cm soil layer, but the total effect in terms of increase in the investigated parameters was not significant. 3) The no-tillage + straw returning and the nitrogen, phosphorus, potassium fertilizers application + straw returning treatments led to more increase in soil fertility with higher increase in integrated fertility index (7.56%-25.93%), they were good choice for improvement of soil fertility in the study sites.