Study On The Optimal Nitrogen Application Rate With N₂O Emission Reducing And Yield Increasing Under Mulching In Potato Field Based On DNDC Model

To explore the optimal nitrogen application rate of both N₂O emission reduction and yield increasing in potato field under no-mulching and mulching treatments at seedling stage,the applicability of De Nitrification-De Composition?DNDC?model to N₂O emission and yield in potato field was verified,and to explore the multifactor effect on N₂O emission and the yield of potato field.In this study,the potato field under natural precipitation in Shenyang was selected as the research object,and four fertilization levels?no nitrogen fertilizer,0 kg?hm-2;low nitrogen fertilizer,75 kg?hm-2;medium nitrogen fertilizer,150 kg?hm-2 and high nitrogen fertilizer,225 kg?hm-2?were designed,with each level under both no-mulching and mulching treatments during the seedling stage.In situ N₂O emission was measured by using static chamber-gas chromatograph technique,and DNDC model was used to further explore the optimal nitrogen application rate of N₂O emission reduction and yield increase in potato field.It is of positive significance to sustainably develop dryland agriculture with coordination of greenhouse gas emission reduction and yield increase in potato field.The results are as follow:?1?The DNDC model can simulate the N₂O emission under different nitrogen levels with no-mulching treatment.Model efficiency EF was 0.45⁰.76 in 2017,and it was 0.41⁰.73 in 2018.Under the condition of mulching treatment at the seedling stage,model efficiency EF was-3.46⁰.57 in 2017,model efficiency EF was-22.52⁰.41 in 2018.The model cannot simulate the N₂O emission in the seedling stage accurately.The DNDC model can both simulate the yield under conditions of no-mulching and mulching treatments.?2?The most significant influence on accumulated N₂O emission are precipitation,soil organic carbon,soil volume-weight and p H,and the most significant influence on yield are precipitation,temperature,CO2 mass concentration and nitrogen application levels during the growth period of potato.?3?Sowing date of potatoes can be set earlier under the normal water supply.Sowing potatoes exceeds 10 ? within 5 days after the 5-day sliding average temperature in this area can ensure the temperature demand of normal growth of potatoes and achieve the purpose of maintaining and increasing yield.?4?It further showed that the nitrogen application rate in the potato field under no-mulching treatment was 90¹05 kg?hm-2 with yield increase as the primary purpose and emission reduction as the secondary purpose,whereas that was 75⁹0 kg?hm-2 with the reverse order of priorities.Because the simulation effect of DNDC on N₂O emission in the potato field under mulching was not good,preliminary results from field data analysis showed that mulching treatment during seedling stage could effectively increase yield and reduce N₂O emission per unit yield.Based on the comprehensive consideration of potato yield and soil N₂O emission reduction,the nitrogen application rate could be increased from 75 kg?hm-2 but less than 150 kg?hm-2.