Effects Of Plastic Mulch On Nitrogen Utilization In Rain-fed Spring Maize Field

Maize?Zea mays L.?is one of the main food crops in rainfed croplands,plastic mulch has been extensively applied in rainfed spring maize fields for it can significantly improve soil water and heat status,thus resulted in the boosting of maize yield.In the present study,field experiment consisting plots and micro-plots was conducted in rainfed spring maize fields.Two treatments,including maize with plastic mulch?PM?and maize?M?,were set up to analyze effects of PM on soil water and temperature,maize yield,water use efficiency,nitrogen gas emission,soil total nitrogen along with its active nitrogen components in rainfed spring maize field.¹⁵N stable isotope tracer technique was utilized to analyze the response of in-season nitrogen uptake and allocation to plastic mulch.The main objective of the present study was to provide scientific support for high efficient utilization of nitrogen in rainfed spring maize field,which could provide theoretical foundation of maize yield improvement by plastic mulch.The findings are outlined as follows:?1?Effects of plastic mulch on soil water heating effect and water use efficiency of spring maize.Soil water conservation by PM was mainly occurred in early and middle stages of maize,during which soil water content?SWC?in topsoil was increased;Soil temperature?Ts?was improved within60 days of plastic film,after 60 days of plastic mulch,soil temperature improvement was not significant.Compared with M,PM increased SWC by 11.8%¹3.0%in seeding stage,7.3%¹2.9%in silking stage at 0²0 cm soil.During the whole maize growth period,average Ts changes of M and PM were consistent with the trend.Within 60 days of film mulching,average Ts of PM was enhanced by 2.0².1?,However,after 60 days of plastic mulching,there was no significance difference in average T_S and daily T_S between of M and PM.Within 60 days of film mulching,the effect of PM treatment on average T_S improvement was mainly observed that PM significantly improved daily T_S during 9:00 to 2:00?the next day?.Compared with M,PM significantly boosted maize yield and water used efficiency?P<0.05?.?2?Effects of plastic mulch on nitrogen gas emission in spring maize farmlands.Film mulching had no significant effect on the cumulative emissions of N₂O and NH₃ in dry spring maize fields.Ammonia volatilization is the primary way of nitrogen gas emission,and nitrogen gas emissionaccounted for 16.1%¹8.5%of in-season fertilizer.?3?Effects of plaistic mulch on soil total nitrogen?STN?and active nitrogen components in soil.PM had no significant effects on STN at 0-30 cm soil,however,it tended to decrease STN below30 cm soil.At harvest,compared with M,PM had no effects on soil particulate organic nitrogen?PON?at 0-10 cm,but PM increased it at 10-30 cm soil by 5.0%²0.8%;PM also increased water extractable organic nitrogen?WEON?at 30-60 cm,decreased it at 0-10 cm.Nitrate nitrogen?NO₃^--N?for both PM and M decreased along with the increase of maize growth and soil depth.PM increased NO₃^--N at 0-30 cm soil in early and middle stage and PM had no effects on NO₃^--N at 0-60 cm at maize harvest.TN had significant correlation with active nitrogen components?PON,WEON and MBN?,PON,WEON and MBN had significant positive correlation with each other,except the correlation between WEON and MBN.?4?Effect of plastic mulch on nitrogen uptake and distribution of spring maize.PM simultaneously increased nitrogen concentration of maize kernels and aboveground nitrogen accumulation.Isotope labeling experiment indicated that PM improved not only in-season fertilizer nitrogen uptake but also soil nitrogen uptake.From the perspective of fate of in-season nitrogen,PM increased in-season fertilizer nitrogen retention at 0-60 cm soil and nitrogen fertilizer recovery efficiency,reduced the risk of in-season nitrogen fertilizer loss.PM increased maize nitrogen uptake,resulting in higher accumulated nitrogen uptake of maize aboveground part?278²97kg/hm²?than applied in-season fertilizer nitrogen?225kg/hm²?,this is not well for soil fertility improvement in the long run.This,further study should be conducted to determine proper fertilization schedule under plastic mulch,to improve maize yield and soil fertility simultaneously.