Effects Of Nitrogen Reduction On Nitrogen Gaseous Loss And Cotton Yield In Drip-irrigated Cotton Field

[Objective]Irrational application of nitrogen fertilizer is often not conducive to crop growth and yield formation.At the same time,it is likely to lead to increased nitrogen loss and increased environmental burden.By studying the effect of nitrogen fertilizer reduction on nitrogen gas loss,cotton yield and fertilizer utilization ratio of drip irrigation cotton field,a rational optimization of nitrogen application in drip irrigation cotton fields was proposed,which provided a scientific basis for the green production and efficiency of nitrogen fertilizer in Xinjiang.[Methods]Field plot experiments were carried out in Tianye Ecological Park in 2019,with a total of six treatments:no nitrogen fertilizer?N0?,no phosphorus fertilizer?P0?,conventional fertilizer nitrogen 300?Farmer's practice fertilization,T300?and 240 kg/hm²?farmer's practice fertilization,nitrogen reduction 20%,T240?,liquid fertilizer nitrogen 300?L300?and 240 kg/hm²?liquid fertilizer,nitrogen reduction 20%,L240?.Each treatment was repeated 3 times,for a total of 18experimental plots with an area of 45 m².[Main results]?1?The content of nitrate nitrogen in soil reached the maximum on the third day after irrigationand fertilization.The content of nitrate nitrogen in T300 treatment soil is the highest,mainlydistributed in 0-40 cm and 60-80 cm soil layers;the content of nitrate nitrogen in 0-40 cm soiltreated by T240,L300 and L240 is higher,lower than 60 cm and little change.Nitrogenreduction by 20%of conventional fertilizer and application of acidic liquid fertilizer cansignificantly reduce soil nitrate nitrogen leaching.Among them,acid liquid fertilizer nitrogenreduction of 20%has the lowest loss of nitrate nitrogen leaching,which is 80.5%lower thanfarmers'conventional fertilization treatment.Compared with the T300 treatment,the residualnitrate nitrogen content in 0-100 cm soil of T240,L300 and L240 treatments decreased by24.5%,18.9%and 35.0%,respectively.?2?The NH₃ volatilization rate of soil reached the maximum on the first day after fertilization,and then gradually decreased.T300 treatment had the highest NH₃ volatilization rate,followed by L300,T240 and L240 treatments.The accumulation of NH₃ volatilization indifferent treatments was 1.3⁵.0 kg/hm².Compared with T300 treatment,the accumulationof NH₃ volatilization in T240,L300 and L240 treatments decreased by 40.4%,25.8%and56.9%,respectively.The acid liquid fertilizer?L300 and L240?treatment reduced the NH₄⁺-Ncontent by 4.5%-42.8%and urease activity by 4.0%-6.7%compared with the correspondingconventional fertilizers?T300 and T240?treatment.Correlation analysis showed that soil NH₃volatilization rate was significantly positively correlated with 0-20 cm soil NH₄⁺-N contentand UR activity.?3?Soil N₂O emission flux reached the maximum on the 3rd day after fertilization,and T300treatment was the highest.The cumulative N₂O emissions from soils treated with T240,L300,and L240 were reduced by 19.9%,14.1%,and 35.0%,respectively,compared with T300treatment.Correlation analysis showed that soil N₂O emission flux was significantlypositively correlated with soil NO₃^--N content and Ni R activity.?4?Compared with farmers'customary fertilization,both nitrogen reduction by 20%ofconventional fertilizer and application of acidic liquid fertilizer can significantly increasecotton yield,especially acid liquid fertilizer nitrogen reduction 20%treatment cotton yield isthe highest,24.5%higher than T300 treatment.The application of acidic liquid fertilizer cansignificantly improve the nitrogen and phosphorus use efficiency of cotton.Compared withT300 treatment,the nitrogen use efficiency of cotton by L300 treatment is increased by 10.1,and the phosphate use efficiency is increased by 13.1 percentage points.The nitrogen andphosphate use efficiency in L240 treatment cotton increased by 8.9 and 7.5 percentage pointscompared with T240 treatment,respectively.Nitrogen reduction will significantly reduce thephosphate use efficiency of cotton,compared with the corresponding fertilization of T300 andL300,T240 and L240 treatments reduced the phosphorus use efficiency by 13.4 and 19.3percentage points,respectively.[Conclusion]Compared with farmers'customary fertilization,the reduction of nitrogen by 20%in acid liquid fertilizer can significantly reduce the loss of nitrate leaching in drip irrigation cotton field,reduce NH₃ volatilization and N₂O emissions,increase cotton nitrogen use efficiency and yield,which is the optimization measure of rational application of nitrogen fertilizer in drip irrigation cotton field.