Effect Of UAN Nitrogen Solution Combined With Urease Inhibitor NBPT On Nitrogen In Soil And Maize

The liquid nitrogen fertilizer UAN nitrogen solution,urea,and new-type urease inhibitors were used as research objects.The methods of indoor constant temperature and humidity culture,pot experiment and ¹⁵N tracer technology were used in the three main agricultural soils of China-grey desert soil,fluvo-aquic soil and red soil.The systematic study on the dynamic effects of UAN nitrogen solution versus urea,UAN nitrogen solution and N-?n-Butyl?thiophosphoric acid triamide?NBPT?on ammonia volatilization and nitrogen transformation and its application on maize were stated.The basic data was provided for China's nitrogen fertilizer reduction,improving fertilizer utilization rate,and promoting development of sustainable agriculture in the paper.The main findings are as follows:1.In constant temperature and humidity conditions,the ammonia volatilization after applyng UAN nitrogen solution in fluvo-aquic soil was greater than that of urea,and vice versa in red soil.In fluvo-aquic soil,the transformation period of UAN nitrogen solution was 7¹4 d,the peak of ammonium nitrogen was on 5⁷ d.After continuous application of nitrogen fertilizer in fluvo-aquic soil,the transformation period was about 3 d,and the peak of ammonium nitrogen was on 0¹ d.In red soil,the nitrogen transformation of UAN nitrogen solution was dominated by the hydrolysis of amide nitrogen,and the transformation period was about 5 days.Compared with urea,UAN nitrogen solution could provide more inorganic nitrogen supplies early after fertilization?0⁷ d in fluvo-aquic soil,0² d after continuous nitrogen application in fluvo-aquic soil and 0²1 d in red soil?of 32.65%⁴0.25%,7.93%¹3.59%and 9.14%¹3.12%,respectively.2.In constant temperature and humidity conditions,NBPT could inhibit the hydrolysis of amide nitrogen in UAN nitrogen solution and reduce its ammonia volatilization.The urease inhibition rates near the peak of ammonium nitrogen were 5.2%³4.29%,3.27%⁹.62%and 27.6%³8.02%,respectively in gray desert soil,fluvo-aquic soil and red soil,and ammonia volatilization decreased by14.89%²1.20%.The inhibitory effect of NBPT in fluvo-aquic soil and grey desert soil were more significant than that of in red soil.The difference in inhibition of 0.8‰NBPT and 1.5‰NBPT in gray desert soil and red soil was not significant,and the inhibition effect of 1.5‰NBPT in fluvo-aquic soil was relatively better than that of 0.8‰NBPT.NBPT showed inhibition on nitrification in fluvo-aquic soil,and the apparent nitrification inhibition rate was 30.94%³1.42%.3.In potting conditions,the application of UAN nitrogen solution promoted the growth of maize and the absorption of nitrogen,phosphorus and potassium by maize in fluvo-aquic soil,and the effect was similar to that of urea.Reducing the application of UAN nitrogen solution by 20%reduced the biomass of maize by 14.71%,and the nutrient uptake of nitrogen,phosphorus and potassium in plants decreased by 24.27%,18.65%and 10.47%respectively.There was no significant change in nitrogen use efficiency.NBPT increased the dry weight of maize roots and the nitrogen accumulation of UAN nitrogen solution in root,reducing its loss rate by 5.55%⁸.82%and having no significant effect on the nitrogen use efficiency of UAN nitrogen solution on maize.Among them,1.5‰,3.0‰,7.0‰and10.0‰NBPT increased the residual rate of UAN nitrogen solution in soil by 4.14%⁶.34%,and there was no significant difference between them.In summary,in constant temperature and humidity conditions,compared with urea,the ammonia volatilization loss was smaller after applying UAN nitrogen solution in southern red soil.And the ammonia volatilization loss was larger in northern fluvo-aquic soil,accounting for 2.38%of the nitrogen application rate.NBPT was beneficial to inhibit the hydrolysis of amide nitrogen in UAN nitrogen solution in gray desert soil,red soil and fluvo-aquic soil,and reduced the ammonia volatilization of UAN nitrogen solution by 14.89%²1.20%.In potting conditions,the fertilizer efficiency of UAN nitrogen solution and urea on maize were similar in the fluvo-aquic soil.The NBPT accounting for 0.8‰¹0.0‰of the amide ammonium?in N terms?could significantly reduce the nitrogen loss rate of maize on the fluvo-aquic soil,1.5‰NBPT was the most suitable ratio.