Effects Of Coated Urea Amended With Inhibitors On Nitrogen Supply And Greenhouse Gas Emission In Spring Maize Fields

Recently,the unreasonable use of chemical fertilizers cause serious problems with the rapid development of agriculture.Researching and developing novel environment friendly slow release fertilizers play important roles in scientific fertilization.In this study,polyvinyl alcohol and polyvinylpyrrolidone were used as coated materials.The inhibitors were added in different ways while coating urea.The pot experiment was included six fertilization treatments:no-urea control?CK?,uncoated urea?U?,polymer coated urea?PCU?,urea coated of mixed polymer and inhibitors?PICU?,urea with double layer coating,polymer on the top of inhibitors?PCIU?,and urea with double layer coating,inhibitors on top of polymer?PCUI?.Dymatic charateristics of soil nitrogen nutrient pools?ammonium nitrogen,nitrate nitrogen,soluble organic nitrogen,microbial biomass nitrogen and fixed ammonium?and gas emission?NH₃,N₂O,CO₂ and CH₄?during the whole maize growing season in different fertilization were studied and thus analyzed the effects of coated urea amended with inhibitors on nitrogen supply capacity and gas emission mitigation potential.Meanwhile,the untilization and allocation of fertilizer nitrogen in soil-maize system were explored by ¹⁵N isotope tracer technology and thus revealed the increasing mechanism of yield and efficiency.The results were as follows:?1?Soil ammonium nitrogen,nitrate nitrogen and soluble organic nitrogen,microbial biomass nitrogen and fixed ammonium had significant relationships?P<0.05 or P<0.01?and maintained a dynamic balance.The concentrations of ammonium nitrogen,nitrate nitrogen and soluble organic nitrogen under all fertilization treatments were at high levels at the seedling stage and decreased gradually with maize growing.Soil microbes and clay minerals could immobilize and release ammonium based on nutrient concentration.After a growing season,the contents of soluble nitrogen?ammonium nitrogen,nitrate nitrogen,soluble organic nitrogen?and immobilized nitrogen?microbial biomass nitrogen,fixed ammonium?under coated urea amended with inhibitors treatments were increased by 30.4%⁴4.6%and 47.5%⁵4.5%,compared with uncoated urea treatment.It improved soil nitrogen supply and played an important role in the effective use of nitrogen.?2?Soil gas emission was significantly affected by soil temperature,water-filled pore space and nitrogen supply?P<0.05 or P<0.01?.Coated urea amended with inhibitors not only delayed the appearance of gas emission peak but also reduced cumulative production.They had more effective abatement capacities than coated urea.Compared with the U treatment,cumulative ammonia volatilization under the PICU,PCIU and PCUI treatments were decreased by 33.9%,44.5%and 30.9%,respectively.Correspondingly,their global warming potentials?GWP?were significantly reduced by 20.4%,24.2%and 17.0%?P<0.05?.?3?Nitrogen uptake by maize under coated urea amended with inhibitors treatments were significantly increased by 2.1%¹4.4%?P<0.05?.Maize yields under the PICU and PCIU treatments were 13.0%and 18.0%higher than U treatment.Meanwhile,¹⁵N uptake by maize grain under these two treatments were increased by 55.7%and 70.3%compared with the U treatment,significantly.Maize ¹⁵N uptake in the PCU,PICU,PCIU and PCUI treatments were31.4%,55.9%,77.1%and 15.5%higher than the U treatment.Their ¹⁵N use efficiency were42.86%,50.85%,57.76%and 37.66%,respectively.Fertilizer nitrogen immobilized by soil microbes and clay minerals could re-release for crop uptake.After a growing season,most of the fertilizer nitrogen remained in soils.Reducing nitrogen input is recommended to promote residual nitrogen utilization and thus achieves zero growth of fertilizer.Therefore,comprehensively considering the gas emission mitigation benefits,crop yield increasing benefits and soil nitrogen supply capacities under the different fertilization in this study,urea with double layer coating,polymer on the top of inhibitors?PCIU?is recommended for optimal fertilization in maize production.It could more effectively reduce ammonia volatilization and greenhouse gas emission.Meanwhile,the PCIU treatment could significantly increase grain yield and nitrogen use efficiency.It is a novel environment friendly and effective fertilization to improve soil nutrient content and regulate soil nitrogen supply.