Effect Of Plastic Film Mulching On Nitrogen Use Efficiency And Balance For Maize In Semi-arid Rainfed Region

Achieving both high yield and high nitrogen use efficiency?NUE?simultaneously has become a major challenge with increased global demand for food,depletion of natural resources,and deterioration of environment.Plastic film mulching have been widely used to increase crop yield in semi-arid regions.Thus,understanding the effects of plastic film mulching on nitrogen use efficiency is important for optimizing nitrogen management strategies.In this study,a three-year field experiment was conducted in Beishan Experimental Station,Yuzhong County,Gansu Province from 2016 to 2018.Six treatments were set up,including four kinds of planting corn treatments,no PM without nitrogen fertilizer?M0N0?,no PM with nitrogen fertilizer?M0N1?,PM without nitrogen fertilizer?M1N0?,PM with nitrogen fertilizer?M1N1?;two no corn treatments,respectively,bare land without PM?BM0?,bare land with PM?BM1?.Through the dynamic changes of plant nitrogen uptake,soil total nitrogen and inorganic nitrogen,we want to find the reasons for the change of nitrogen use efficiency?NUE?under the PM.The meta-analysis method was used to compare the two popular tillages in the rain-fed areas,the PM and conservation tillage's yield and the nitrogen use efficiency.The main conclusions are as follows:1.PM significantly increased the surface soil temperature during the growing season.Compared with the corresponding M0N0,M0N1,and BM0,M1N0,M1N1,and BM1 had an average temperature increase of 2.60°C,2.48°C,and 3.24°C for the entire growing season.The warming effect in the early growth season was more obvious.The three year average temperature increase in April-July were 3.20°C,3.08?and3.94°C.2.The PM significantly increased the soil water content and water use efficiency of profile 0-2 m.In the case of no application of nitrogen fertilizer,the average water use efficiency of the PM was increased by 298.9%compared with no PM;in the case of nitrogen application,the PM increased by an average of 396%for 3 years.3.Both PM and nitrogen application significantly increased crop yield and total biomass at harvest.In the no nitrogen fertilizer treatment,the PM yield increased by an average of 313%over the past three years compared with the no PM;in the nitrogen fertilizer treatment,the PM increased by 448.7%on average in three years.The PM also significantly increased the 100-grain weight,and the nitrogen fertilizer increased the 100-grain weight significantly only in 2018.4.The PM increased the nitrogen partial productivity?PFP_N?,agricultural nitrogen efficiency?NAE?.The PFP_N with PM increased by 482%,758%,and 106%compare with no PM.The PM increased the nitrogen use efficiency?NUE?in 2017.In the 2018,the PM had no significant effect on NUE.5.The PM significantly increased the total nitrogen uptake of the plant and the nitrogen harvest index?NHI?.In the case of nitrogen application,total nitrogen uptake with PM increased by 249%and 25.6%in 2017 and 2018,respectively,and NHI increased by 94.7%and 18.2%,respectively.And the PM could increase the post-silking nitrogen uptake and N remobilization during grain-filling.6.The PM reduced the 0-10 cm soil total nitrogen significantly regardless of nitrogen application.In the case of nitrogen application,it was found that NO₃-N accumulation occurred in the 30-50 cm soil layer at the 2016 and 2017 harvest periods.7.According to the nitrogen balance formula:the PM in 2017 and 2018significantly reduced the nitrogen loss of the plant-0-50 cm soil system.In the two years,they were reduced by 75%and 16%respectively.8.The results of meta-analysis showed that the yield and nitrogen use efficiency of the PM increased by 64%compared with the no PM.The conservation tillage had no significant effect on the yield and nitrogen use efficiency compared to the traditional tillage.At the same time,the PM also significantly increased yield and NUE compared to conservation tillage.In areas with low rainfall,the effect of PM on yield and NUE was significantly higher than that in high rainfall areas;conservation tillage in areas with high rainfall significantly reduced corn yield and NUE compared to traditional tillage.In the case of high nitrogen application,the effect of the film on the yield and NUE was higher than that in the case of low nitrogen application.In soils with high clay content,the effect of film mulching on yield and NUE was significantly higher than soil with low clay content.In summary,the PM improves the nitrogen use efficiency of maize by increasing N uptake and N remobilization,reducing the accumulation of soil NO₃-N in the deep layer and reducing the apparent loss of nitrogen.Meta-analysis results show that from the perspective of yield and nitrogen use efficiency,plastic film mulching has more advantages in rainfed areas.