| To evaluate the effect on soil fertility in paddy rice upland wheat rotation double cropping system with double zero tillage, Conventional soil testing method, Biology ECO and Densitometer methods were used to investigate the contents of nutrients in soil, siol structure and activities and diversity of soil microorganism. The results showed that, compared with traditional farming system (CK), the contents of soil organic matter, total nitrogen, total phosphorus, available nitrogen and available phosphorus increased by 11.9%, 17.1%, 9.2%, 26.5% and 19.1%, respectively, within 0~40 cm depth soil layer after four year double zero tillage cropping in succession with winter wheat rice rotation system. Meanwhile, total potassium and available potassium decreased by 0.9% and 10.2%, respectively. Within soil layer of 0~20 cm, the proportions both clay soil and sand particles increased but proportions of silt particles decreased in the double zero tillage cropping system, compared with CK. The metabolic diversity of functional microorganism in the soil and its biological activity were significantly greater than that under traditional farming system. The changes based on Shannon Wiener, Pielou, Richness and Simpson measurements of metabolism diversity of functional microorganism were consistent across soil layers 0~20 cm and 20~40 cm with that in the whole wheat growth season.The indices were higher at tillering and jointing stages of winter wheat for traditional farming treatment, whereas they were higher at grain filling and maturing stages for the four year double zero tillage cropping treatment. The results also showed that the soil fertility of four year double zero tillage cropping was distinguishably better than that of three year double zero tillage cropping. In conclusion, four year double zero tillage cropping benefited soil fertility, especially at the middle and late growth stages of winter wheat. |
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