Effects Of Tillage Methods On Soil Organic Carbon Pools And Aggregate Stability

Mankind processed different tillages and optimized soil structure according to the theory of systems engineering and ecology-economics in the central area of Loess Plateau of China, which not only controlled the loss of soil water and improved soil environment, but also increased crop income and soil structure stability. Conservation tillage is not only the factor that affects soil development, but one of important ways to improve soil the physical and chemical properties and crop yields in aridity agriculture area of loess plateau. We determined the soil organic carbon,distribution of soil water-aggregates,organic carbon of aggregates and active organic carbon under different tillage ways in the central area of Gansu. The purpose of this article was studying the effects of the stability of soil aggregate and the pool of the organic carbon, which may be gained from two factors, one was to know the reason of stability of soil aggregate and its appraising, the other was to study the effects of conservation tillage on the pool of carbon. The main conclusions were as fellows:1 Effects of tillage methods on soil organic carbon poolsCompared with Conventional tillage with no straw, No-till with straw cover,Conventional tillage with straw incorporated and No-till with no straw cover all increased soil organic carbon contents under two kinds rotation sequence, but No-till with straw cover to be more advantageous to improving the soil organic carbon.Under wheat/pea/wheat (W/P/W) rotation sequence, compared with Conventional tillage with no straw, No-till with straw cover, Conventional tillage with straw incorporated and No-till with no straw cover increased soil organic carbon contents by 4.64%,3.78% and 2.19% respectively. Under pea/wheat/ pe(aP/W/P)rotation sequence, compared with Conventional tillage with no straw, No-till with straw cover, Conventional tillage with straw incorporated and No-till with no straw cover increased soil organic carbon contents by 4.34%,14.16% and 8.91% respectively.Compared with Conventional tillage with no straw, No-till with straw cover,Conventional tillage with straw incorporated and No-till with no straw cover all increased contents of microbial biomass carbon of soil under two kinds rotation sequence, but No-till with straw cover, Conventional tillage with straw incorporated and No-till with no straw cover to be more advantageous to developing the content of microbial biomass carbon of soil. Under wheat/pea/wheat(W/P/W)rotation sequence, compared with Conventional tillage with no straw, No-till with straw cover, Conventional tillage with straw incorporated and No-till with no straw cover increased contents of microbial biomass carbon of soil by 69.67%,48.14% and 33.22% respectively. Under pea/wheat/ pea(P/W/P)rotation sequence, compared with Conventional tillage with no straw, No-till with straw cover, Conventional tillage with straw incorporated and No-till with no straw cover increased contents of microbial biomass carbon of soil by75.57%, 45.57% and 36.42% respectively.2 Effects of tillage methods on water-aggregate stabilityCompared with Conventional tillage with no straw, No-till with straw cover,Conventional tillage with straw incorporated and No-till with no straw cover all increased contents of >0.25mm soil water-aggregates and mean weight diameter(MWD), and contents of >0.25mm soil water-aggregates of 0-5cm layer has significantly increased the content of >0.25mm soil water- stable aggregates of 5-10cm and 10-30cm layer in every treatment. The analysis result showed that No-till with straw cover, Conventional tillage with straw incorporated and No-till with no straw cover to be more advantageous to developing >0.25mm soil water-stable aggregates, and >0.25mm soil water-stable aggregates are highly positive correlated with mean weight diameter.3 Effects of tillage methods on soil organic carbon of aggregatesUnder wheat//pea/wheat(W/P/W)and pea/wheat/pea(P/W/P)rotation sequence, Compared with Conventional tillage with no straw, No-till with straw cover,Conventional tillage with straw incorporated and No-till with no straw cover increased organic carbon contents of soil aggregates and significant difference. In four treatments, the organic carbon content of soil aggregates in 0-5cm layer was higher than 5-10cm and 10-30cm layer. The result showed that the stability of aggregates was increased with content of organic carbon, so the stability of soil structure was also improved.4 Effects of tillage methods on active organic carbon and carbon pool management indexCompared with Conventional tillage with no straw, No-till with straw cover,Conventional tillage with straw incorporated and No-till with no straw cover improved the contents of soil active organic carbon under different tillage methods. The research results showed that No-till with straw cover, Conventional tillage with straw incorporated and No-till with no straw cover to be advantageous to developing the contents of soil active organic carbon. However, its can be also advantageous to increased carbon pool management index, especially the straw cover was important factor for increasing carbon pool management index.