Effect Of Urease Inhibitor On Reducing Nitrogen Losses And Improving Nitrogen Use Efficiency

Globally nitrogen?N?is considered as a key nutrient for maintaining higher crop production to meet the food demand of increasing population of the world,and economic feasibility of the agricultural system.Agriculture is the most significant source of ammonia volatilization to the atmosphere,which is associated with many environmentally deleterious effects,including soil acidification,loss of biodiversity,eutrophication of aquatic systems,and the formation of fine particulates.It also acts as a secondary source of nitrous oxide emissions from ammonia deposition,which contributes to climate change and global warming leading to human health risks.The use of urease inhibitor and nitrification inhibitor have the potential to reduce N losses by ammonia volatilization to the atmosphere and nitrate leaching into surface and ground water bodies,thereby improve N use efficiency.The efficiency of urease inhibitor is dependent on crop,soil and environmental conditions.The Loess Plateau has semi-arid and sub-humid climate;the soils are calcareous soils with high texture.Ammonia volatilization is a major N loss pathway from soil in this region.Therefore,we have studied the effects of urease inhibitor on reducing N losses and improving N use efficiency in Loess Plateau with field and incubation methods.The main conclusions included:1.Field experiments were carried out at different three sites?Yangling,Zhouzhi-1,and Zhouzhi-2?of Loess Plateau during summer maize crop,to evaluate the effectiveness of N-?n-butyl?thiophosphoric triamide?NBPT?and combined use of NBPT+Dicyandiamide?DCD?with urea on nitrogen transformation and reducing NH₃ volatilization in soils of different physico-chemical properties,and under different environmental conditions.Four treatments including Control?no N?,N-220 kg ha^-1?N-220?,N-220+NBPT and N-220+NBPT+DCD were applied in two split doses?70%and 30%as first and second topdressing,respectively?through band placement method.The cumulative ammonia volatilization from urea alone was observed 65.8 NH₃-N kg ha^-1?29.9%of N applied?,40.5 NH₃-N kg ha^-1?18.4%of N applied?and 20.1 NH₃-N kg ha^-1?9.2%of N applied?in Yangling,Zhouzhi-1,and Zhouzhi-2 sites,respectively.The application of NBPT significantly reduced ammonia volatilization ranged by 80-93%and combined use of NBPT and DCD with urea-N fertilizer reduced 75-90%.Hence,the NBPT and combined use of NBPT and DCD have significantly reduced ammonia volatilization.The climatic factors such as precipitation,air temperature,and wind speed significantly affected on ammonia volatilization.These results suggested that the amendment of urea with NBPT and NBPT plus DCD have potential as a strategy to mitigate NH₃-N losses and enhancing N use efficiency in different soils and climatic conditions.2.Summer maize crop was grown at three sites?Yangling,Zhouzhi-1,and Zhouzhi-2? of the Loess Plateau,having different soil properties and climatic conditions.The objectives was to evaluate the efficacy of urea treated with NBPT and mixture of NBPT+DCD on soil N transformation,N uptake and N use efficiency?NUE?.The application of urea treated with NBPT alone and a mixture of NBPT+DCD maintained the soil mineral-N content for a longer time,which resulted in more N uptake by the plant,and eventually improved NUE.The application of urea treated with NBPT and mixture of NBPT+DCD increased grain yield ranged 37.7-48%and 15-20%compared to control and urea,respectively.The higher plant N uptake was observed in urea treated with NBPT+DCD,followed by U+NBPT.The application of urea treated with NBPT and NBPT+DCD increased NUE by 13.8-21.6%and14.3-22.6%,respectively,compared to unfertilized control.The NUE was higher?5.3-10%?in NBPT+DCD and NBPT?4.8-8.4%?,compared to urea alone.Consequently,the application of urea treated with NBPT and mixture of NBPT+DCD in splits,through subsurface band placement represented the best approach for improving N uptake,NUE,and yield of the maize crop.3.We have conducted incubation study,to evaluate the efficiency of urease inhibitor ?NBPT?on NH₃ volatilization from the different calcareous soils of the Loess Plateau,widely differing in physical and chemical properties,such as soil texture,pH,organic matter content and urease activity.The cumulative NH₃ volatilization loss in urea applied soils was 42.8-56.1mg kg^-1?21.4-28%of applied N?.The application of NBPT with urea slow downed urea hydrolysis,and significantly reduced NH₃-N loss by 47.1-55.5%in different soils.This study validated that NBPT application has immense potential in mitigating NH₃ volatilization from different calcareous and alkaline soils.