Effects Of Covering Methods On Spring Water And Fertilizer Use Efficiency And Soil Enzyme Activities In Weibei Dry Plateau

Mulching measures are important measure to preserve water and increase yield in the northwestern drylands,but the mechanism of yield increase and the effects on soil nutrients and enzyme activity are not clear;Based on the positioning experiment in 2012,this study carried out a field experiment with spring maize as the research object at the Changwu County Ecological Experiment Station in Shaanxi Province.There were three treatments: no mulching(CK),straw mulching(SM)and plastic film mulching(FM).Growth status,nitrogen uptake,and dynamic distribution of water and fertilizer in the soil,combined with microbial carbon,nitrogen,and phosphorus limits to respond to different mulch patterns in 2017-2019,so as to select a suitable mulch pattern for dry-cultivated spring maize,to achieve high agricultural yields and efficient resource utilization The high-yield and high-efficiency corn in northwest dryland provides a theoretical basis.The main conclusions are as follows:(1)Plastic mulching and straw mulching can significantly improve the SPAD,leaf area index and plant height of spring maize in each growth period,and enhance the photosynthetic capacity of spring maize,making spring maize plants have higher dry matter accumulation.Compared with bare land,the average yield and biomass of mulching during the two years increased by 31.7% and 42.5%,respectively,while those of straw mulching increased by 8.2% and 10.1%,respectively.(2)Compared with the non-covering treatment,the nitrogen transport volume and nitrogen transport efficiency of vegetative organs covered by straw were increased by 42.49% and 16.17% respectively;The nitrogen transport volume,nitrogen transport efficiency and nitrogen assimilation volume of vegetative organs covered by plastic film mulching increased by 67.8%,22.47% and20.4%,respectively,through the "source-sink" synergy to increase grain nitrogen accumulation and grain yield.Straw mulching and plastic film mulching treatments increased the nitrogen accumulation of 16.1% and 45.2% of the above-ground parts of plants without mulching treatment,respectively.(3)Plastic mulching and straw mulching treatment increased water consumption of spring maize before silking stage,the ratio of water consumption before silking stage to the water consumption after silking stage was also increased,thus reduced the influence of drought stress on spring maize in early flowering stage.WUE of straw mulching and plastic mulching treatment increased by 6.1% and 12.9%,respectively,compared with that of non-mulching treatment.(4)The nitrate nitrogen accumulation of 0-100 cm soil layer without covering treatment,straw covering treatment and plastic film covering treatment accounted for 52.4%,57.0% and 70.3% of the nitrate nitrogen accumulation of 0-200 cm,respectively;The nitrate nitrogen accumulation of straw covering and plastic film covering 100-200 cm was reduced by 55.0% and 64.7% compared with the treatment without covering.Plastic film mulching and straw mulching treatment significantly reduced the accumulation of soil nitrate nitrogen in the 0-200 cm soil layer;the covering measures reduced nitrate nitrogen leaching and alleviated groundwater pollution.(5)Compared with CK,soil organic carbon and total nitrogen under straw mulch increased by 9.7% and 7.8% in average for each period.The organic carbon,total nitrogen and total phosphorus under plastic film mulch were reduced by 5.6%,4.8% and 2.8%,respectively.Compared with CK,the C-and N-acquiring enzyme activities under the plastic film mulch were reduced by 20.5% and 5.2%,respectively.The alkaline phosphatase(P-acquiring)enzyme activities under straw mulch and plastic film mulch were increased by 2.7% and 13.5%,respectively.Plastic film mulch increased the phosphorus limitation,mainly because of good soil hydrothermal condition,and the soil water content and temperature were increased by FM,compared to CK 17.6% and 9.0% increase for CK,respectively,which promoted the utilization of soil available P by maize.Plastic film mulch further induced low SOC due to accelerated decomposition of organic matter in early years,thereby increased P limitation for soil microorganisms.The long-term straw mulching increases the soil organic matter due to the annual input of organic matter,and the decomposition of organic matter releases available P which alleviates the P limitation of microorganisms.Therefore,under mulching conditions,the SOC content of alkaline soil in arid farmlands is the main factor leading to microbial P restriction.In summary,straw and plastic mulching improved water use efficiency,reduces nitrate leaching and increase crop yields.However,film mulching excessively depletes soil organic matter,while straw mulching increases soil nutrient content.