Experimental Study On Fertilizer Nitrogen Utilization From Different Water And Nitrogen Regulation Models In Cold Region Paddy Rice Field

Rice is the main food crop in China,and the planting area is extensive.Rice production will not only consume a lot of water resources,but also need a lot of fertilizer nitrogen.Therefore,it is of great significance to improve the absorption rate of nitrogen in fertilizer by reasonable irrigation and fertilization,and to systematically analyze the recovery efficiency and loss of fertilizer nitrogen in rice-soil system,so as to reduce the negative impact on ecological environment in the process of rice production.This research combined field experiments with micro-area test.The traditional flooding irrigation was used as the control,set three N rates（85,110,135 kg/hm2）and three ¹⁵N-labelled fertilizer application treatments was conducted in rice with different fertilizer-N recovery efficiencies.The fertilizer-N recovery efficiencies of total fertilizer was measured,and the fertilizer-N recovery efficiencies of basal,tillering and panicle fertilizations were analyzed by applying ¹⁵N-labelled urea as basal,tillering or panicle fertilizer,and comparative study of the two kinds of irrigation fertilizer under different nitrogen utilization rate,and the residue of fertilizer nitrogen in paddy soil after rice harvest was studied,and the distribution of fertilizer nitrogen in 0⁶0 cm soil in paddy field was investigated.The results are as follows:（1）The model of rice control irrigation significantly increased the amount of dry matter accumulation,total nitrogen accumulation and yield of rice on the ground,and played the role of "water saving and high yield",and the proportion of fertilizer nitrogen in the total nitrogen accumulation of rice under different nitrogen application was about 11.20%²2.86%,and the difference between different irrigation modes was not significant.The total nitrogen utilization rate of fertilizer in rice treated by different nitrogen application levels was 29.89%³6.12%,base fertilizer nitrogen utilization rate was 10.91%¹5.36%,the nitrogen utilization rate of tiller fertilizer was 34.84%³6.90%,and the nitrogen utilization rate of spike fertilizer was 50.27%⁶3.54%,Correlation analysis showed that the total utilization rate of nitrogen in fertilizer was positively correlated with the utilization rate of tiller fertilizer and spike fertilizer nitrogen.（2）The residual rate of base fertilizer nitrogen in paddy soil was 36.0%³9.9% under different nitrogen application levels,the residue rate of tiller fertilizer nitrogen was 54.9%⁵7.3%,the residue rate of spike fertilizer nitrogen was 29.4%³5.4%,and the total residue rate of fertilizer nitrogen in soil was 35.4%³7.1%,Under the same nitrogen application,the residue rate of fertilizer nitrogen in soil was higher than that of conventional flooded irrigation,and the residue of fertilizer nitrogen in the same depth soil layer was significantly different under the same nitrogen application level,and the base fertilizer,tiller fertilizer applied in rice growth period under different nitrogen application The residues of spike fertilizer nitrogen in the surface soil（0²0 cm）of paddy field were higher than that in conventional flooded irrigation mode,while the residue in 20⁴0 cm and 40⁶0 cm soil layer was lower than that of conventional flooding irrigation.Correlation analysis showed that the total residue of fertilizer nitrogen in soil was positively correlated with the residual amount of fertilizer nitrogen in soil in each period,and there was a significant positive correlation with the residue of base fertilizer and spike fertilizer nitrogen in the surface soil.（3）The accumulation of soil inorganic nitrogen and fertilizer nitrogen residues in inorganic nitrogen morphology in soil profile increased with the increase of nitrogen application,and less with the increase of soil depth in rice controlled irrigation mode.The accumulation of inorganic nitrogen and fertilizer nitrogen residues from inorganic nitrogen in the surface soil（0²0 cm）of rice controlled irrigation mode under different nitrogen application levels was higher than that of conventional irrigation,and the total accumulation of inorganic nitrogen and NO₃^--¹⁵N in 20⁴0 cm and 40⁶0 cm soil layer was lower than that of conventional irrigation,and between different irrigation modes.There was no significant difference in the cumulative amount of NH₄⁺-¹⁵N in 60 cm soil layer（P<0.05）.The NO₃^--¹⁵N accumulation of 20⁴0 cm soil layer in conventional irrigation mode under the same nitrogen application was 10¹1 times higher than that of controlled irrigation mode,and the NO₃^--¹⁵N accumulation of 40⁶0 cm soil layer increased by nearly 3 times times compared with that of controlled irrigation mode.Under different nitrogen application,the nitrogen accumulation in rice ripening period was 77.77%⁸4.51% from soil nitrogen,which increased 12.91%²3.12% compared with conventional irrigation,and the effective "A" value of soil nitrogen in the control irrigation mode of rice under the same nitrogen application was 9.41 higher than that of conventional irrigation mode respectively 9.41%,5.65% and 3.69%.The results show that,in addition to the low utilization rate of base fertilizer nitrogen in rice controlled irrigation mode,the total nitrogen utilization rate of fertilizer,tiller fertilizer and the nitrogen utilization rate of spike fertilizer are better than that of traditional submerged irrigation,so that the nitrogen of fertilizer is used efficiently and the risk of environmental pollution caused by nitrogen residue of fertilizer is reduced.The model of rice control irrigation can improve the residue of fertilizer nitrogen in root soil（0²0 cm）,reduce the loss of nitrogen in fertilizer,and the residual fertilizer nitrogen can supplement the soil nitrogen bank in black soil area to a certain extent,which is beneficial to the protection of paddy soil and the improvement of fertility in black soil area.The model of rice control irrigation can effectively improve the effectiveness of nitrogen in paddy soil,increase the accumulation of inorganic nitrogen in surface soil,and reduce the leaching loss of nitrogen in fertilizer,and play the role of water saving and emission reduction.