洞庭湖区典型稻田玉米水稻轮作下土壤—作物系统对施氮措施的响应OA北大核心CSTPCD

[Objective]Crop yield increases and soil organic matter decreases when double rice cropping system shifted to wet and dry rotation cropping system,but little information is known that the effects of chemical fertilizer nitrogen combined with different organic materials on crop yield,nitrogen use efficiencies and organic matter content under the wet and dry cropping system.[Method]The maize and rice rotation was regarded as object,five treatments were set up,including no nitrogen fertilizer applied(CK),only chemical fertilizer applied(NPK),NPK plus straw return(NPKS),NPK plus manure(NPKM)and NPK plus biochar(NPKB)in purple clayey soil and reddish clayey soil in Dongting lake plain from 2015 to 2021.The changes of yield,nutrient use efficiency,soil carbon and nitrogen content as well as carbon and nitrogen balance under different fertilization treatments were explored.[Result]The average maize yield,rice yield and total annual yield in the six-year in purple clayey soil and reddish clayey soil were 5.7,7.3 and 12.9 t·hm-2,respectively.Moreover,the three yields above in purple clayey soil were slightly higher than that reddish clayey soil,though the differences in both soils were not significant.Compared with the NPK treatment,NPKM treatment significantly(P＜0.05)increased the average yields in maize season or rice season in the two soils(P＜0.05)by 10.6%and 4.20%,respectively.Among all the treatments,NPKM treatment had the maximum yield in the maize season,and the value was 6.0 t·hm-2;and NPKB treatment had the maximum yield in the rice season,and the value was 7.5 t·hm-2.The six-year average annual total yield under NPKM and NPKB treatments was significantly higher(P＜0.05)than that under other treatments,respectively,but the difference between NPKM and NPKB treatments was not significant.Compared with the other treatments,NPKM treatment significantly(P＜0.05)improved the chemical fertilizer nitrogen recovery efficiency,agronomic efficiency and partial productivity in maize,rice,the six-year average values of maize season were 66.3%,39.5 kg·kg-1 and 56.0 kg·kg-1,respectively,and the six-year average of rice season was 53.8%,21.9 kg·kg-1 and 68.6 kg·kg-1,respectively.NPKB treatment had significant higher chemical fertilizer N agronomy efficiency and partial productivity than the NPKS and NPK treatments in maize and rice seasons,and compared with NPK treatment,the nitrogen recovery rate of maize was also significantly improved.Soil organic carbon and total nitrogen content decreased significantly from the fourth years(the year of 2019).Compared with the soil organic carbon and nitrogen content between the beginning of the experiment(2015)and 2021,the annual average soil organic carbon in all the N applied treatments in purple clayey soil and reddish clayey soil decreased by 1.8 and 0.7 g·kg-1,and total nitrogen content decreased by 0.4 and 0.1 g·kg-1;the NPKM treatment in both the soils had the lowest decrease of soil organic carbon and total nitrogen,and the NPKB treatment was the second.The loss of soil organic carbon and total nitrogen in the NPKM treatments were the lowest,which were 0.48 t C·hm-2·a-1 and 94.7 kg N·hm-2·a-1,respectively.[Conclusion]After the double rice cropping system shifted to wet and dry rotation cropping system,the chemical fertilizer nitrogen combined with manure and biochar could increase crop yield and hold back the decrease of soil organic matter,NPKM treatment had the maximum average maize yield and NPKB treatment had the maximum average rice yield during the experimental period.