| Nitrogen plays an important role in crop growth and increased yield,but the excessive amount of nitrogen fertilizer in rice production in my country will increase nitrogen loss and cause environmental hazards.The Northeast single-cropping rice area is a high-quality rice producing area in my country.Although the soil fertility is high and the regional nitrogen application rate is low,due to the poor early-stage fertilization capacity of the soil under cold conditions in cold areas,the release of fertilizer nutrients is slow,and there are also low fertilizer utilization efficiency.problem.Using appropriate methods to reduce the application of nitrogen fertilizer is of great significance for improving the efficiency of rice production in the single-cropping rice area in Northeast China,reducing environmental risks,and achieving sustainable rice production and regional green development.This study clarified the characteristics of nitrogen fertilizer application in the northeast single-cropping rice area through farmer surveys,cultivation experiments and field experiments,studied the potential and ways of reducing nitrogen fertilizer application between regions,and formed a nitrogen fertilizer reduction and efficiency increase and precise application technology in the northeast single-cropping rice area.The main findings are as follows:（1）Results of survey regarding on the N fertilization input and rice production are summarized as follows.From south to north,the proportion of basal fertilizer gradually decreased and the timing of basal fertilizer application gradually advanced.Moreover,the N application rate showed a decreasing trend from south to north.The average N application rate is 243.7 kg·hm-2,162.8 kg·hm-2 and 142.8 kg·hm-2 in the rice area of Liaoning,Jilin and Heilongjiang province.The grain yield in Liaoning,Jilin and Heilongjiang province was 9485.7 kg·hm-2,8185.7 kg·hm-2 and 7629.4 kg·hm-2,respectively.The average crop N requirement in Liaoning,Jilin and Heilongjiang province was 193.3 kg·hm-2,156.4kg·hm-2 and 133.2 kg·hm-2,respectively.The theoretical optimal N application rate in Liaoning,Jilin and Heilongjiang province was 183.6-203.0 kg·hm-2,148.6-164.2 kg·hm-2 and 126.5-139.9 kg·hm-2,respectively.Therefore,there was a high theoretical N application reduction potential in Liaoning province.The current average N application rate in Jilin province was very close to the theoretical N application rate.Heilongjiang province had some N fertilization reduction potential.（2）The surface soil of 12 typical rice growing areas in Northeast China was collected,through soil organic nitrogen mineralization culture and soil microbiology analysis,so as to clarify the contribution of soil background to the differences of nitrogen application among regions.The results showed that after56 days of N mineralization culture,the rate of soil mineralization at each point in the single cropping rice area in Northeast China showed a trend from fast to slow.The total amount of soil mineralized N at each point at the end of the experiment was between 10.1 and 14.2 mg·kg-1,which was much lower than the initial amount of mineralized N.Redundancy analysis showed that soil alkali-hydrolyzed nitrogen and C/N were significantly correlated with nitrogen mineralization capacity.AOA is the dominant bacteria in the process of soil ammonia oxidation in Northeast single-cropping rice region,and there is an inhibitory relationship between AOA and AOB.nir K is the dominant gene that reduces NO2-to NO in single cropping rice region of Northeast China.There were no significant differences in soil mineralization amount and mineralization potential,and there was no obvious spatial heterogeneity in soil microbial community structure.（3）Potential of nitrogen fertilizer reduction in rice in southern Northeast China.Based on the statistical analysis of the survey data of the typical rice production area in Liaoning province,the Liaohe River Delta rice area,and combined with the field experiment,the effects of replacing chemical fertilizer with slow-release fertilizer on nitrogen reduction on yield,nitrogen absorption and utilization and loss risk were studied.The results showed that the average nitrogen application rate was 294.5 kg·hm-2 in the Liaohe River Delta rice region.The theoretical suitable nitrogen application rate was 182～202 kg·hm-2,and there was 30.5%～38.3%room for theoretical nitrogen reduction.Compared with the regional average N application rate,each slow-release fertilizer reduced N by 28.7%～38.9%,which could maintain the rice yield and crop N absorption,ensure the crop N supply,and improve the N fertilizer use efficiency.Moreover,reducing N within the target yield would not lose soil fertility.It can effectively reduce the nitrogen content of surface water in the early stage of fertilization and the average nitrogen concentration of surface water in the whole growth period,reduce The Times of fertilization and reduce labor cost,increase the income of 541.4～5816.6 yuan per hectare and realize cost saving and efficiency increase.（4）Potential of nitrogen fertilizer reduction in the northern rice region of Northeast China.Field experiment was conducted to study the effect of slow-release fertilization and side deep fertilization under a low N application rate on the economic and environmental benefits in cold cultivated rice areas.Results showed that the N application rates in the cold areas were relatively low,and there was a small N application reduction potential.Applying a reduced N application rate in a conventional way would harm the sustainability of rice production.With a 15%reduction in N application rate,compared with the traditional chemical fertilization treatments（NPK）,managed N fertilization treatments（DT）（80%N provided by slow‐release N fertilizer with deep placement was applied as basal fertilizer and 20%N provide by urea as tillering fertilizer）sustained the rice yield and rice N uptake,guaranteed the nutrient supply in the middle and late stages of rice growth,and promoted the rice height,improve N use efficiency.The value and the lasting time of N peak in field water were decreased.NH3 emissions in rice season was reduced by 4.63%-21.25%.Fertilizer N loss as NH3volatilization was decreased by 0.9%-5.92%.TN and Olsen-P in soil were increased.4.63%～21.25%NH3 emission and 0.9%～5.92%ammonia volatilization nitrogen loss rate in rice growth period,improve soil fertility,maintain reasonable nitrogen surplus,increase the income of 497.20～1235.58 yuan per hectare,realize cost saving and efficiency increase.In conclusion,the application of reasonable fertilizer types,fertilization methods and nitrogen fertilizer operation mode can achieve high yield and high efficiency under the theoretical optimum nitrogen application amount. |
