Influences Of Rainfall Harvesting And Straw Mulching On Corn Growth, Water And Nitrogen Use On Black Soils Of Northeast Corn Belt

The corn belt of northeast China is the most importment corn production in China, accounting for32%of the total corn production and produing50million ton corn residues annually. The unreasonable use of residue will lead to resource waste and serious air pollution. The site is located in the north temperature zone and has a semi-humid continental monsoon climate. Precipitaition various widely between seasons and years, seasonal drought frequently occurs during the crop growth season. In this research, we attempt to solve the seasonal drought and guide local corn straw management through ridge and furrow planting and straw mulching managements.In this study, field experiments were conducted in2011and2012in Lishu county to study the effect of ridge and furrow rainfall harvesting and straw mulcing on corn growth and water and nitrogen use under rainfed conditions. The treatments included flat planting bed (FB), flat planting bed with straw mulching on soil surface (FM), plastic-mulched ridges with bare furrows (RFB), and plastic-mulched ridges with straw-mulched furrows (RFM). Based on the field experiment we calibrated and validated RZ-SHAW model to simulate the effect of year, straw mulching rate, initial soil water content and their interaction effect on corn yield. The following lists the major results from this research:(1) The precipitation during corn growth period in2011and2012were371and410mm and the corn was not subjected to drought stress in two seasons. Ridge and furrow planting and straw mulching significantly improved soil water conditions and increased water infiltration. The RFB and RFM treatments increased relative soil water content relative to FB treatement. The addition of straw mulch to the furrows did not consistently affect the soil water content. The FM treatment increased relative soil water content at corn seedling and jointing stages and had no significant effect at later stages.(2) Ridge and furrow planting and straw mulching significantly affected soil temperature at corn early stages. The RFB treatment increased soil temperature relative to FB treatment. The RFM treatment decreased soil temperature relative to RFB treatment. The FM treatment significantly decreased soil temperature at seedling and jointing stages relative to FB treatment.(3) Ridge and furrow planting and straw muching had no effect on soil inorganic nitrogen content in2011. In2012, the RFB and RFM treatment decreased soil inorganic nitrogen content at corn jointing and filling stages. There had no significant differences between RFB and RFM treatments. The FM treatement decreased soil inorganic nitrogen content at cron jointing and filling stages. The nitrogen mineralization was higher in RFB and RFM treatments than in FB treatement, and the nitrogen uptake by corn plants was lower in RFB and RFM treatments than in FB treatment. The FM treatment decreased nitrogen mineralization and had no effect on other nitrogen balance items relative to FB treatment.(4) Ridge and furrow planting dereased the evapotranspiration and increased the WUE by12-13%in2011. The RFB and RFM treatments decreased corn yield by30%and33%, decreased WUE by24%and28%, and decreased NUE by38%and39%in2012. The additional straw mulching in furrows had no effect on corn yield and water and nitrogen use efficiency. Straw mulching had no effect on total evapotranspiration. The FM treatment decreased corn yirld by18%-26%, decreased WUE by16%-21%, and decreased NUE by21%-27%. Therefore, ridge and furrow planting and straw mulching are not recommended for black soil when soil water is sufficient for corn growth.(5) The parameters were determined with2011field data of FB and FM treatemtns when using RZ-SHAW model to simulate the effect of straw mulching on black soil of northeast China. The root mean square error (RMSE) between simulated and measured soil water content in different depths was ranged from0.009-0.045and0.015-0.047cm cm-3, and that between simulated and measured biomass was1692and785kg ha-1, and that between simulated and measured LAI was0.653and0.500, and that between simulated and measured yield was220and118kg ha-1. The parameterized model was tested using data of FB and FM treatments in2012. The RMSE between simulated and measured soil water content in different depths was ranged from0.015-0.027and0.013-0.029cm3cm-3, and that between simulated and measurd biomass was2580and1362kg ha-1, and that between simulated and measured LAI was0.484and0.382, and that between simulated and measured yield was495and190kg ha-1. That means the RZ-SHAW model is suitable for simulating straw mulching management on black soils of northeast China.(6) Using RZ-SHAW model simulated the effect of year, straw mulching rate, initial soil water content and their interaction effect on corn yield and water use efficiency. The results showed that corn yield was affected by precipitation, maxmum average daily temperature, daily radiation, and relative humidity. The simulated results of30years showed that straw mulching increased yield in5years, decreased yield in4years, and straw mulching had no effect on yield in21years; straw mulching increased WUE in10years, decreased WUE in3years, and straw mulching had no effect on WUE in17years. The corn yield and WUE was not only affected by precipitation during growth season but also precipitation before sowing. Water supply must be considered to ensure the corn yield and WUE when the initial soil water content was low. From the results,80%of field capacity is the optimum initial soil water content and straw mulching rate of6kg ha-1is the optimum rate to ensure the corn yield and WUE.