Effects Of Slow And Controlled Release Nitrogen Fertilizers On Yield And Greenhouse Gas Emission Of Spring Maize In Weibei Dryland Under Plastic Film Cultivation

Plastic film mulching is one of the effective ways to increase crop yields and environmental benefits in the Weibei Dry Highland.The reason is that film mulching increases soil temperature and water use.However,it also increases the difficulty of topdressing.Therefore,most of the fertilizers are applied at one time under film mulching conditions.However,the one-time application of fertilizer will reduce fertilizer utilization,so the use of slow and controlled release nitrogen fertilizers to improve fertilizer efficiency and reduce fertilizer losses has become an important research goal in this area.Therefore,overall,applying slow and controlled release nitrogen fertilizers under film mulching conditions in the Weibei Dryland can increase crop yields and environmental benefits.In this study,spring maize was used as the research object at the Changwu Loess Plateau Agricultural Ecological Experiment Station of the China Academy of Sciences,Changwu County,Shaanxi Province.The experiment set up urease inhibitor NBPT,nitrification inhibitor DCD and DMPP,and coated slow-release nitrogen fertilizer RCN,SCN these 5 slow and controlled release nitrogen fertilizers.Under the black and white film mulching,the 20%nitrogen reduction and the slow and controlled release nitrogen fertilizer was applied at one time to explore the effects on spring maize yield,maize growth characteristics,soil nitrate nitrogen content and greenhouse gas emissions.The purpose is to screen out suitable slow and controlled release nitrogen fertilizers varieties and dosages,and ultimately achieve high yield and high efficiency in spring maize production.The research has achieved the following results:（1）The yield under the black mulch film was increased by 22.28%on average compared with the flat without mulch,while the white mulch yield increased by 20.03%on average（Table 2-7 and Table 2-8）.This result shows the black mulch film is better than the white mulch film in terms of increasing yield in this two-year field trial.Film mulching can increase the dry matter accumulation,spring maize plant height and leaf area index during the growth period of spring maize.Among them,the urease inhibitor NBPT under the black mulching film can maximize the increase of dry matter accumulation.Although the black mulching film is better than the white mulching film in terms of plant height,there is no significant difference.The leaf area index also has the same result.（2）Film mulching can reduce the amount of soil nitrate nitrogen leaching.The black mulching can reduce the downward leaching of the NO₃^--N in the lower soil during the critical growth period of spring maize.Under the white mulching film,the NO₃^--N content at60～100cm is more than the black mulching film.This result shows that white mulching film will enhance the leaching of soil nitrogen.The dynamic distribution of NO₃^--N is basically the same under different mulching films of slow and controlled release nitrogen fertilizers.Nitrification inhibitors and urease inhibitors reduce the NO₃^--N content of the soil surface,while the coated slow-release urea has a relatively large amount of NO₃^--N content in the surface soil at the later stage of spring maize growth because of its longer fertilizer efficiency（Fig 3-1 and Fig 3-2）.（3）As the mulching increases the soil temperature,the greenhouse gas emissions also increase.The N₂O and CO₂ emission fluxes under different nitrogen application treatments show obvious changes with time.Nitrogen fertilizer application will significantly increase the cumulative emissions of N₂O and CO₂,GWP and GHGI.But slow and controlled release nitrogen fertilizers will reduce the cumulative emission of N₂O and the N₂O emission coefficient（Table 4-4 and Table 4-5）.Among the various slow and controlled release nitrogen fertilizers,urease inhibitor NBPT has the best effect.Compared with the 20%nitrogen reduction model,the cumulative N₂O emissions,GWP and GHGI are reduced by 52.11%,62.12%and 64.29%,respectively（Table 4-4 and Table 4-5）.In summary,under the mulching film,20%reduction in nitrogen combined with various slow and controlled release nitrogen fertilizers can meet the nutrient requirements of the crops during the entire growth period.Among them,the black mulch film is superior to the ordinary white mulch film in terms of spring maize yield,dry matter accumulation and environmental benefits.Among the five slow and controlled release nitrogen fertilizers,urease inhibitor NBPT can significantly reduce soil greenhouse gas emissions.It shows that the use of black mulch film and urease inhibitor NBPT can be one of the methods for reducing nitrogen and increasing efficiency in the farmland of Weibei Dryland.