| The soil tillage modes and straw-returning are the two important agronomic measures by agricultural production. In order to explore the effects of different tillage measures and straw-returning on the soil nutrient, microorganisms and organic carbon pool in a farmland with rice-wheat double cropping, the experiment was conducted at changwang village of YouFang town in yangzhong city of Jiangsu province from November in2009to June in2012. The paper studied the effects of two tillage modes (plowing tillage and rotary tillage) and four straw-returning ways (no straw-returning, the rice straw-returning in the wheat season, the wheat straw-returning in the rice season, straw-returning in the wheat and rice season) to soil nutrient, microbial biomass C、N, enzyme activity and soil organic carbon pool with rice and wheat farmland by field experiment, analyzing the acting force tillage modes and straw-returning to the content of soil nutrient and organic carbon pool and studying preliminarily different tillage measures and straw-returning to soil fertility effects and mechanisms on rice-wheat rotation farmland. The main results are as follows:1. The straw-returning in the wheat and rice season can significantly improve soil fertilityStraw-returning significantly increase soil total nitrogen, available nitrogen, total phosphorus, available phosphorus and available potassium. Whether it is plowing tillage and rotary tillage, the content of soil nutrient is straw-returning in the wheat and rice season>straw-returning in the wheat or rice season>no straw-returning. In rice season, in addition to the available nitrogen, the soil nutrients is plowing tillage higher than rotary plowing; but in the wheat season, the content of available phosphorus is rotary tillage significantly higher than plowing tillage, and other nutrients had no significant difference; and in addition to total phosphorus, soil total nitrogen, available nitrogen, available phosphorus and available potassium under plowing tillage with straw-returning in the wheat and rice season. While in the wheat season, the content of soil total nitrogen, total phosphorus and available phosphorus under rotary tillage with straw-returning in the wheat and rice season are highest. And available phosphorus under rotary tillage treatment is significantly higher than plowing tillage; other nutrients have no significant difference.In the rice and wheat season, straw-returning have highly significantly force to soil nutrient and the force is17.93%～90.51%; tillage factors have highly significantly force to available phosphorus and available potassium and the force are10.01%and15.61%.Whether it is in the rice or the wheat season, with the increase of soil depth, the content of soil total organic carbon (TOC) and labile organic carbon (LOC) decreased gradually. Straw-returning in each soil layer have remarkable effective on soil and straw-returning have the maximum force. In0-7cm soil, TOC and LOC under plowing tillage with straw-returning in the two seasons are highest in the rice season; in the wheat season, in addition to the water-soluble organic carbon (WSOC), soil organic carbon (TOC), easily oxidizable organic carbon (EOC) and water-soluble organic carbon (WSOC) under rotary tillage with straw-returning in the two seasons are highest. In7-14cm soil, in the rice season, TOC and WSOC under plowing tillage with straw-returning in the two seasons are highest, but EOC and MBC (microbial biomass carbon) under rotary tillage with straw-returning in the two seasons are highest. In the wheat season, TOC, EOC and MBC under rotary tillage with straw-returning in the two seasons are highest, but WSOC under plowing tillage with straw-returning in the two seasons are highest. In14-21cm soil, in the rice season, TOC and LOC under plowing tillage with straw-returning in the two seasons are highest; in the wheat season, TOC and MBC under plowing tillage with straw-returning in the two seasons are highest, but EOC and WSOC under rotary tillage with straw-returning in the two seasons are highest.2. The straw-returning in the wheat and rice season can significantly improve the content of microbial biomass C, N and enzyme activityWhether it is in the rice reason or wheat reason, the content of soil microbial biomass carbon under plowing tillage and rotary tillage are significantly higher than other treatments. In rice season, soil microbial biomass nitrogen under rotary tillage with rice straw-returning in the wheat season significantly higher than other treatments; but in the wheat season, soil microbial biomass nitrogen with plowing tillage and rotary tillage with straw-returning in two seasons significantly higher than no straw-returning. In rice season, the activity of soil unease under rotary tillage with rice straw-returning in the wheat season is highest; but in the wheat season, the activity of soil unease under rotary tillage with straw-returning in the two seasons is highest. While in the rice reason or wheat reason, the activity of soil catalase under plowing tillage with rice straw-returning in the wheat season is highest, and the activity of soil invertase glucose under rotary tillage with rice straw-returning in the wheat season is highest and was significantly higher than plowing tillage with no straw-returning in the two season. |
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