Effects Of Straw Returning And Irrigation Methods On Water And Nitrogen Use Efficiency And Soil Quality In Root Soil Layer Of Spring Maize

In view of the problems of continuous increase in yield of grain and amount of straw caused by expansion of maize planting area and low utilization of straw and the inefficient utilization of water and fertilizer under the traditional irrigation methods,the test was carried out in Tongliao National Agricultural Science and Technology Park from 2019 to 2020 using Nonghua 101 as experimental materials by adopting sub-plot design with straw returning（S⁺）and straw leaving（S^-）as main plot and traditional border irrigation（F）and shallow drip irrigation（D）as sub-plot.Effects of straw returning and irrigation methods on photosynthetic physiology,biomass accumulation,soil physical and chemical properties,and water and nitrogen use efficiency of spring maize were investigated.The main research results are as follows:1.Under the same irrigation method,the leaf area index and SPAD value of spring maize under the straw returning are significantly higher than that of straw leaving,and the rate of leaf senescence is 3.4%lower than that of straw leaving.In2020,the population photosynthetic potential,canopy photosynthetic capacity and photosynthetic rate of straw returning are all significantly higher than that of straw leaving,and the amount and rate of dry matter accumulation,amount and rate of transport,root dry weight during silking stage,and ratio of root and shoot were also significantly higher than that of straw leaving.Under the straw turning,the leaf area index,SPAD value of ear leaf and the leaf under the ear position,the photosynthetic rate in milk maturity stage,the intercellular CO₂concentration,the population photosynthetic potential and the photosynthetic capacity of the canopy,and the accumulation and transportation of dry matter under the shallow buried irrigation were all significantly higher than that of the traditional border irrigation.2.Under the same irrigation method,straw returning can significantly increase grain yield and water and nitrogen use efficiency of spring maize.Compared with straw leaving,yields of shallow drip irrigation and traditional border irrigation under the straw returning increased by 1.95% and 6.91%,irrigation water use efficiency increased by 1.9%and 6.9%,and the agronomic utilization efficiency of nitrogen fertilizer increased by 6.2%and 3.4%as well.The straw returning promoted the absorption and transfer of nitrogen nutrients,and the contribution rate of plant nitrogen accumulation,transfer and transfer to the grain were significantly higher than that of straw leaving.Compared with traditional border irrigation,shallow drip irrigation under straw return significantly increases grain yield,water and nitrogen use efficiency and total nitrogen accumulation of plants before silking,in which grain yield increased by 2.6%,irrigation water use efficiency increased by 70.9%,and nitrogen fertilizer agronomic efficiency increased by 15.2%,while the physiological use efficiency of nitrogen and nitrogen harvest index decreased by 17.5%and 0.7%.3.Under the same irrigation method,the aggregate mass fraction in the 0.25-2mm particle size range,R_0.25%（agglomerate content greater than 0.25 mm in diameter）and MWD（average mass diameter of aggregates）of straw returning were all significantly higher than that of straw leaving,and the bulk density of 20-40 cm soil layer was significantly lower than that of straw leaving while the soil porosity of 0-60cm soil layer was significantly higher than that of straw leaving.Under the straw returning,the aggregate mass fraction,MWD and GMD（geometric mean diameter of aggregates）,aggregate organic carbon storage and carbon sequestration capacity of each particle size aggregate under shallow drip irrigation were all significantly higher than that of traditional border irrigation,and the soil bulk density of 40-60 cm soil layer and the soil compactness below the 20 cm soil layers were significantly lower than that of traditional border irrigation,and the three-phase soil of 0-20 cm soil layer was more ideal than that of traditional border irrigation.4.Under the same irrigation method,the soil moisture of each soil layer during the silking period were significantly higher than that of the straw leaving.The content of total nitrogen,available nitrogen and nitrate nitrogen in 0-20 cm soil layer were all significantly higher than that of the straw leaving while the content of ammonium nitrogen in 0-20cm soil layer was significantly lower than that of straw leaving the field.Under the straw returning,water content of 20-30 cm soil layer,total nitrogen and available nitrogen content of 0-60 cm soil layer and ammonium nitrogen content of 0-20 cm soil layer of shallow drip irrigation were significantly higher than that of traditional border irrigation in the seedling stage while The soil nitrate nitrogen content of 40-60 cm soil layer was significantly lower than that of traditional border irrigation.In summary,straw returning and shallow drip irrigation can be used as the best planting methods to increase the capacity of photosynthesis and biomass accumulation of spring maize,improve the physical and chemical properties of the soil,and increase the yield and efficiency of water and nitrogen use of spring maize.