Effects Of Urea Ammonium Nitrate Solution On N Uptake, Fate And Yield Of Spring Maize

Increasing nitrogen fertilizer application plays an irreplaceable role in increasing crop yield and improving economy.In recent years,the amount of nitrogen fertilizer on farm reached 27.9 million tons in China,the use of urea accounted for about 67% of them.However,in the US over the past 40 years,65% nitrogen fertilizer is liquid nitrogen and urea ammonium nitrate solution（UAN）accounted for half of it.It reduces the evaporation and concentration process of producing urea and ammonium nitrate in the process of UAN production,which saved the energy and cost and gradually become the main development direction of nitrogen fertilizer.However,the development of UAN is in the initial stage in our country,the transformation mechanism and application effect is not clear.Therefore,¹⁵N labeled micro-area experiment and cultivation were conducted by adopting the combination of field experiments to study the application effect,distribution,utilization,transformation and ammonia volatilization of UAN on spring maize in order to provide the theory basis and technical support for application of UAN on the maize.The main research results are as follows:1.UAN application can increase the maize yield,improve the absorption and utilization rate of nitrogen,reduce the soil nitrogen accumulation and ammonia volatilization,and optimize nitrogen balance.The climate was arid in 2015,UAN with one-time and split fertilization compared with urea,yield increase were 6.1%,3.6%,respectively,nitrogen content of plant increased 10.2 kg/hm2 and 10.9 kg/hm2,soil nitrogen residues were decreased by 18.8%,9.9%,ammonia volatilization reduced by 18.2%,11.0%,respectively;the climate was humid in 2016,yield had no difference with single fertilization between UAN and urea,but the yield of UAN with split fertilization increased 7.5% compared with urea,nitrogen content of plant by UAN increased 2.3 kg/hm2 and 26.0 kg/hm2,soil nitrogen residues were decreased by 14.5%,20.9%,ammonia volatilization losses were reduced by 4.5% and 8.1%;Accumulation of dry matter and yield showed the same trend in two years;utilization efficiency of UAN can be increased by 4.9-11.1 percentage;the apparent residual rate reduced by 4.6 percentage and the apparent loss rate reduced by 4.2 percentage.Compared with urea treatments,UAN treatments showed similar or higher maize grain yields and plants N uptake in black soil region when applied with same rates and methods,meanwhile soil N residual and surplus were relatively lower,and thereby resulting in higher N use efficiency and better environmental effect.2.The results of ¹⁵N micro-area experiment showed that compared with urea,the utilization efficiency and the nitrogen distribution in plant of UAN were relatively higher.The utilization rate of urea was 37.6%,and the utilization rate of UAN was 45.1%,in which the use efficiency of urea,ammonium nitrogen,nitrate nitrogen and ammonium nitrate in UAN were 22.1%,12.1%,10.8% and 23.0%,respectively.The distribution with ¹⁵N labeled urea in straw,leaves and grains were 3.2%,7.1% and 27.3%,respectively;the distribution with ¹⁵N labeled UAN in straw,leaves and grains were 4.4%,9.3%,and 31.4%,respectively.The distribution of urea,ammonium nitrogen,nitrate nitrogen and ammonium nitrate with UAN in straw were 4.1%,4.6%,5.2%,5.2%;in leaves were 9.2%,8.6%,10.8%,10.7%;in grains were 29.5%,36.4%,28.4%,31.5%,respectively.3.Ammonia volatilization characteristics of urea ammonium nitrate solution on different soil types were researched by indoor constant temperature cultivating method.In this study,ammonia volatilization characteristics of urea and UAN were affected by soil types and moisture.The results showed that under the same soil moisture,ammonia volatilization rate and accumulation of UAN were lower than urea of equal nitrogen in chernozem,black soil and albic soil,ammonia volatilization accumulation decreased by 24.7%,38.2%,26.3%,respectively.In the black soil and chernozem,ammonia volatilization accumulation of UAN with low field water capacity treatment was higher than that with high field water capacity treatment,increased 42.5% and 29.7%,respectively.But there was no significant difference in albic soil.The ammonia volatilization rate and accumulation of UAN in three different types of soil showed: chernozem>black soil>albic soil.Compared with urea,ammonia volatilization loss of UAN was lower in three kinds of soil types,especially in black soil and albic soil.