| Currently, cultivation with plastic mulching has become an important way to increase crop output on the semi-arid and sub-humid areas Loess Plateau of China. Double ridges and furrows mulched with plastic film is one of the mulching tillage method and has been widely used in rainfed agriculture area by ridge and furrow covered with film and sowing in furrow, inhibiting water evaporation, redistributing precipitation from ridges to furrows and raising soil temperature, and increasing grain yield significantly. However, it needs to deplete soil nutrients to improving nutrient transformation and nutrient use efficiency while reducing the amount of plant residual, causing soil fertility degradation.Straw can be input soil to enrich soil fertility and improve environment as renewable biological resources, therefore, straw returning is one of good choice for sustainable development of dryland agriculture. In order to further support land use and develop ecological agriculture, one experiment was established to explore application of straw returning and plastic film mulching coupling effect on soil fertility, growth and yield of corn in different sites of Ningxian, Chongxin, Tongwi, Huining and Yuzhong from2008to2012. To evaluate the feasibility that introduce straw returning to maize cultivation system of double ridges and furrows mulched with plastic film. The test design included four treatments:no straw returning and no film mulch (CK), straw Returning (S), film mulch (M), straw returning plus film mulch (S+M), three repeat and random arrangement. Besides Yuzhong, other experimental sites are mulching in autumn, straw returning and exchange new film after the harvest of next year. To analyze of crop yield and soil nutrient transformation of four years (three years of Ningxian, over in2011), and the following results are obtained:1. In this case, straw returning amount is300-500kg/mu (dry weight), straw moisture content is60-80%, it is a better effect and no adverse action on the growth and yield of maize.2. Mulching effect on corn yield significantly and less impact of straw returning. Compared with CK, S+M, M and S improved average grain yield by44-137%,34-129%and12-22%, respectively; and improve total biomass47-88%,38-80%and10-14%, respectively, grain yield increased by34-75%in Ningxian and Chongxin, and95-137%in Tongwi, Huining and Yuzhong under mulching, indicating that the significant effect of increase maize output in semi-arid areas than sub-humid areas.3. Soil daily average temperature was increased in plow layer with mulching in maize initial stage of growth, especially0-5cm soil layer, which increased average daily temperature by2.4-5.8℃.Compared with CK, water use efficiency improved by30-122%with mulching and improved by10-15%under straw returning. However, Effect of straw returning on soil temperature was not obvious.4. Straw returning and mulching all increased the amount of nutrient uptake. Compared with CK, S+M, M and S improved N uptake by47-101%、41-92%and10-18%;P uptake by44-113%、35-103%、11-19%. N use efficiency and P use efficiency improved with plastic mulching by5.3-24.0%,5.2-15.5%, respectively; Effect of straw returning on nutrient use efficiency was not obvious.5. In comparison with CK, the content of soil organic carbon, total nitrogen, light organic carbon, particles organic carbon improved with straw returning by2.4-2.9%,4.5-4.9%,25.7-40.4%and5.4-11.7%respectively after four years of planting corn, Straw returning had significant effects on carbohydrate and increased by11-36%at harvest from the second growth season. On the other hand, the content of soil organic carbon, total nitrogen, particles organic carbon was decreased with plastic film mulching by1.3-2.3%、5.7-7.3%and8.9-13.2%respectively. Little change of light organic carbon between years and reduced by8.6-15.7%in the same year, the harvest Compared with sowing. Effect of mulching on carbohydrate was not significantly.6. Compared with CK, M and S improved cumulative respiration in10-day incubation from0-15cm depth by7-12%and2-19%, respectively; plastic film mulching and straw returning are improved the soil microbial biomass carbon, β-glucosidase, alkaline phosphatase and urease activity respectively,and significant effect on the Enzyme activity in straw returning than mulching.7. Soil inorganic nitrogen content improved with mulching which is3-22times than CK in the0-15cm soil; and soil inorganic nitrogen content was reduced with Straw returning, but there is no significant difference between treatments. Plastic film mulching and straw returning can increased Soil mineralization rates, compared with CK, M and S improved Soil N mineralization in10-day incubation from0-15cm depth by12-54%and13-39%, respectively;These results suggest that double ridges and furrows mulched with plastic film mulching can increased crop yield by preserving soil moisture and increasing soil temperature, promoting mineralization of organic matter, improving water use efficiency and nutrient use efficiency, but reducing the soil organic matter content at the same time. On the other hand, straw returning can increased soil organic matter content by stimulating microbial activity, improving mineralization rates.and can compensate for the loss of soil nutrients caused by the plastic film mulching, but there is no ideal to control moisture and temperature of soil,and to Improve nutrient use efficiency. If we combination with double ridges and furrows mulched with plastic film mulching and straw returning, it may be a new cultivation mode in dryland agricultural. |
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