Study On Balance And Residual Efficiency Of Fertilizer Nitrogen In Brown Soil Under Long-term Fertilization And Rotation

The application of chemical fertilizer,especially nitrogen fertilizer,plays a crucial role in promoting the development of modern agriculture.Nitrogen is a necessary nutrient element in the process of crop growth and development.In agricultural production,the rational application of nitrogen fertilizer plays an important role in increasing crop yield and improves crop quality.However,at present,there is an unreasonable fertilization period and fertilization method in China.Fertilization and severe loss of nitrogen fertilizer after fertilization,the application of nitrogen fertilizer has serious irrationality.It has important guiding significance for the development of a reasonable fertilization scheme for the corn-soybean rotation system in the brown soil region of Northeast China,which provides a scientific basis for sustainable management of farmland nitrogen and sustainable agricultural development.This study is based on a long-term field trial of typical brown soil fertilizer for 39 years in Northeast China,the 12 treatments are:N,NP,NPK,M₁N,M₁NP,M₁NPK,M₂N,M₂NP,M₂NPK,to clear the effects of different fertilization methods on nitrogen utilization in soybean and corn seasons.At the same time,the micro-plot experiment was set up in the field,and the ¹⁵N isotope tracer method was used to label the fertilizer N,the 6 treatments are:N,NP,NPK,M₁N,M₁NP,M₁NPK.The nitrogen of the different crop rotation systems was quantified under different fertilization conditions,and the effects of different fertilization methods on the nitrogen transfer law of fertilizer were determined.The main conclusions are as follows:?1?Long-term rotation fertilization field trial found that under the treatment of high and low organic fertilizers combined with chemical fertilizers,the biomass,yield,N uptake of soybean were significantly higher than those of single chemical fertilizer and no fertilization treatments,and M₁NPK treatment was highest.Corn has the highest total N uptake.Under different fertilization treatments,the N uptake of various organs of soybean was grain>pod>stem,and the N uptake of various organs of corn was grain>stem.The nitrate content of soybean in the fertilizer season and the low organic fertilizer area did not change much compared with that before sowing,while the nitrate content of 0-100 cm in the high organic fertilizer area decreased compared with that before sowing.The M₁NPK treated soybeans had the highest residual nitrate N content in the 0-100 cm soil,and the highest M₂NPK treatment in the corn harvest period.The soil nitrate N content in the organic fertilizer area was higher than that in the soybean harvest period.The content of ammonium N in soil was less.The content of ammonium N in M₁NP treatment was the highest in the soybean harvest period,and M₂NP treatment was the highest in the corn harvest period.At the harvest stage of soybean and corn,the soil microbial biomass nitrogen content in the 20-40cm soil layer was lower than that in the 0-20 cm soil layer.The soil microbial biomass nitrogen content of M₂NPK was the highest in the 0-20 cm soil layer,the M₂treatment wasthe highest in the 20-40 cm soil layer.And during corn harvest period,the M₁NPK treatment was the highest in the 0-20 cm soil layer,and M₂NP was the highest in the 20-40 cm soil layer.It can be seen that under the corn-soybean rotation system,the organic fertilizer combined with chemical fertilizer treatment can not only increase the yield and N absorption of soybean and corn,but also fertilize the soil and reduce losses.?2?The ¹⁵N-labeled micro-plot experiment in the field showed that organic fertilizer combined with chemical fertilizer can increase the biomass,yield and N uptake of soybean,corn.The average N use efficiency of soybean fertilizer application and organic fertilizer combined with chemical fertilizer treatment are 22.1%and 44.2%,respectively,and in the corn season,it was 38.8%and 45.7%,of which M₁NPK treatment was the highest,which was significantly higher than other treatments.During the soybean harvest period,the residual amount of ¹⁵N in soil fertilizer of 0-40 cm was 13.3?20.0 kg N ha^-1,and the residual rate was44.3%?64.8%.The residual amount of fertilizer N in fertilizer treatment was significantly higher than that in organic fertilizer.During the corn harvest period,the residual amount of¹⁵N soil fertilizer was 50.1?70.9 kg N ha^-1,and the residual rate of fertilizer N was41.8%?59.1%.The N use efficiency of soybean season and corn season was 20.0%?51.7%and 33.4%?51.1%,respectively.The utilization rate of M₁NPK treatment was the highest,which was significantly higher than other treatments.The loss rate of fertilizer ¹⁵N in soybean season and corn season was 3.98%?16.31%and 4.25%?12.97%,respectively,and M₁NPK treatment was the lowest.It can be seen that the proper amount of organic fertilizer combined with NPK fertilizer can increase the yield of soybean and corn and reduce the N residue and loss of fertilizer.?3?The total soil residual rate of fertilizer N in the corn season that residual in the soybean season was 48.4%?83.8%.Compared with the soybean season,the decrease rate of soil residue in organic fertilizer area?19.4%?34.8%?was significantly lower than that in the chemical fertilizer area?63.1%?106.8%?.The residual fertilizer N utilization is6.86%?13.55%,and the loss rate is 5.67%?44.69%.The loss rate of organic fertilizer area is lower than that of chemical fertilizer area.It can be seen that the application of proper amount of organic fertilizer can reduce the loss of residual fertilizer N and reduce the residual fertilizer N downward migration.In summary,in the corn-corn-soybean rotation system in the brown soil region of Northeast China,application of organic combined with chemical fertilizers?NPK?in the corn season,especially with the appropriate amount of organic fertilizer(13.5 t ha^-1),and NPK fertilizer alone in the soybean season can not only increase soybean and corn yield,N uptake,but also fertilize the soil,reduce the nitrate leaching and fertilizer N loss.It is a better fertilization method.