Study On The Effective Utilization Of Nitrogen In Spring Wheat-Silage Maize

【Objects】To explore spring wheat-silage maize from the aspects of plant total nitrogen,soil ammonium nitrogen and nitrate nitrogen,soil N₂O and ammonia volatility through the combination of different N application rates and N application frequency in the two seasons of pro-spring wheat and post-silage maize.The combination of high yield and high efficiency of N application and fertilization frequency provides a theoretical basis for the efficient use of nitrogen fertilizer for spring wheat-silage maize in drip irrigation in northern Xinjiang.【Methods】The experiment was carried out by two factors:nitrogen application rate and nitrogen application frequency.The pure N application amount 0(N_w0),300(N_w1)and 450(N_w2)kg/hm² was applied to the top of the experiment.The N frequency of the facility is 5 times(T_w1),4 times(T_w2),and 3 times(T_w3).There are 9 treatments in total.After the treatment,the pure nitrogen application rate is 0(N_c0),300(N_c1)and 450(N_c2)kg/hm²,based on the amount of N applied,the facility N frequency was 5 times(T_c1),4times(T_c2),and 3 times(T_c3),for a total of 81 treatments.To explore the effects of different soil available nitrogen（ammonium nitrogen,nitrate nitrogen）,plant nitrogen,gaseous nitrogen volatility（N₂O,NH₃）,yield and NUE under different treatments,in order to obtain the best N application before and after the season.The combination of quantity and N application rate provides a theoretical basis for rational nitrogen application under drip irrigation spring wheat-silage corn mode.【Main results】（1）Temporal and spatial distribution characteristics of soil available nitrogen:1)From the time dimension,the soil nitrate N and ammonium N content increased with the increase of N application rate in spring wheat season,and did not change with the increase of N application frequency;The soil nitrate N content increased first and then decreased with the growth period,and the ammonium N content increased gradually.The content of nitrate N and ammonium N in silage maize season increased with the increase of N application rate,and decreased with the increase of N application rate.The content of soil nitrate N and ammonium N decreased with the growth period.2)From the perspective of spatial distribution,the soil nitrate N content in the spring wheat season gradually decreases with the deepening of the soil layer,mainly concentrated in the 0-20 cm soil layer.Under the N treatment,the soil nitrate N content advances with the growth period.The trend of gradual migration to the deep layer,the ammonium N content does not change much within the soil layer.The nitrate N content in the silage maize season decreased with the deepening of the soil layer,and the ammonium N content did not change significantly with the deepening of the soil layer.The soil N_w2T_w3 treatment（450 kg/hm²,3 times）had the highest content of nitrate and ammonium in the soil,and the mature period was 74.50 kg/hm²,21.29 kg/hm²,and the silage maize N_c2 T_c3 treatment（225kg/hm²,2 times）the soil nitrate N and ammonium N content were the highest and the maturity period was52.33 kg/hm² and 4.16 kg/hm².（2）N aspect of plants:1)From the perspective of N application rate,the N accumulation of spring wheat and silage maize plants increased with the increase of N application rate,N application significantly increased the nitrogen accumulation of the plants,and the difference in the treatment of each N application was significant.2)From the frequency of N application,the N accumulation rate of spring wheat increased significantly after flowering stage,and the N accumulation of plants with 4 times(T_w2)was the largest.With the increase of N application rate,the N content of silage maize plants increased first and then decreased.The N content of the plants was the highest when N application(T_c2)was applied.3)From the N accumulation of the annual plant,with the increase of N application rate,the N accumulation of the crops in the early growth stage（jointing stage）increased gradually,and the N content of crop plants had no obvious effect on the late growth stage.（3）Law of gaseous N loss:The ammonia volatility rate,the proportion of N application rate and the annual ammonia volatility accumulation of the spring wheat and the post-salted silage corn increased with the increase of N application rate,and the frequency of nitrogen N application decreased with the increase of N application rate.1)Soil ammonia volatile law:The peak ammonia volatility rate,ammonia volatility accumulation,N application rate and annual ammonia volatility accumulation in spring wheat season were 3.89 kg/hm²,16.92-26.28 kg/hm²,6.32%-8.76%and 6.90%-10.71%.The peak rate of ammonia volatility rate,the accumulation of ammonia volatility,the proportion of N application and the cumulative amount of annual ammonia volatility in silage maize season were 3.99 kg/hm²,9.12-24.65 kg/hm²,8.70%-12.50%and3.72%-10.05%.The peak period of soil ammonia volatility rate under different N application rates and N application frequency appeared in the first 2-3 days after fertilization and irrigation.N application significantly promoted soil ammonia volatility.The peak ammonia volatility of spring wheat under different N application rates and N application rates appeared in the filling stage and maturity stage,and the re-seeding silage corn season appeared in the jointing stage and harvest stage.3)The average N₂O emission flux,emission accumulation and annual N₂O accumulation in the spring wheat season were 26.52-106.55μg·m^-2·h^-1,5.57-21.31g/hm²,3.18%-12.16%.The average N₂O emission flux,emission accumulation and annual N₂O accumulation in the spring wheat season were 26.52-106.55μg·m^-2·h^-1,5.57-21.31 g/hm²,3.18%-12.16%.The average N₂O emission flux,emission accumulation and annual N₂O accumulation in silage maize season were 23.76-91.60μg·m^-2·h^-1,5.06-18.32g/hm²,2.89%-10.46%.The N₂O emission flux,cumulative emissions and annual emission ratio of the early spring wheat and silage corn increased with the increase of N application rate in the first 3 days,increased with the decrease of N application frequency,and oxidation after 3 days.N emissions are rapidly decreasing.The N₂O emission flux peaks and the N application frequency were all observed in the jointing stage and the mature stage.The silage corn appeared in the jointing stage and harvest stage.The annual ammonia volatility accumulation in the spring wheat season was 11.4%higher than that in the silage corn season,and the cumulative N₂O emission in the spring wheat season was 5.7%more than the silage maize season.The ammonia volatility change and the N₂O emission flux of the different N application frequency were synchronized with the N application rate in the N application period.（4）Yield and NUE:When N application was applied at 300 kg/hm² for 4 times,the N application rate and N application frequency were the highest in spring wheat season.When N application was applied at150 kg/hm² for 3 times,the N application rate and N application rate were the highest in silage maize season.The reason is suitable that the application of N in the spring wheat was 300 kg/hm² for 4 times and the silage corn was 150 kg/hm² for 3 times.【Conclusions】N application significantly increased plant total N content,soil available N content and gaseous N volatility.The appropriate N application rate under the same N application rate could reduce soil N and gaseous N loss.The suitable N application scheme for the mid-seasonal repetitive system in this experiment is 4 times of 300 kg/hm² for the first sputum and 3 times for the 225 kg/hm² after the sputum.