Mitigating nitrous oxide emissions from a maize-cropping black soil in northeast China by a combination of reducing chemical N fertilizer application and applying manure in autumn(Fertilizers and soil amendments)

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Nitrous oxide (N_2O) emissions from agricultural soils, mainly caused by chemical nitrogen (N) fertilizer inputs, are major sources of N_2O in Chinese terrestrial ecosystems. Thus, attempts to reduce N_2O emissions from agricultural soils by optimizing N applications are receiving increasing attention. Further, organic fertilizers are being increasingly used in China to improve crop production/quality and prevent or reduce soil degradation. However, organic and chemical fertilizers are often both applied in spring in northeast China, which promotes N_2O emissions and may be sub-optimal. Therefore, we hypothesized that reducing applications of chemical fertilizer N and applying manure in autumn could be an effective strategy for mitigating N_2O emissions from cropped soils in the region. To test this hypothesis, we established a field trial to investigate the effects of different combinations of chemical N fertilizer applications and animal manure in autumn on both N_2O emissions and maize (Lea mays L.) grain yields in northeast China. The treatments, expressed as NxMy (where Nx and My denote the total amounts of chemical fertilizer nitrogen (N) and manure (M) applied in kg N ha^<-1> and m^3 M ha^<-1>, respectively), were N_0M_0, N_<230>M_0, N_<270>M_<12>, N_<230>M_<15> N_<320>M_<18> in 2010 and N_0M_0, N_<230>M_0, N_<200>M_<12>, N_<200>M_<15>, N_<280>M_<18> in 2011. Measurements of the resulting N_2O emissions showed that pulse fluxes occurred after each chemical N fertilizer application, but not after manure inputs in autumn or during soil-thawing periods in the following spring. Emission factors for the chemical fertilizer N were on average 1.07% (1.00〜1.10%) and 1.14% (0.49〜1.83%) in 2010 and 2011, respectively. Furthermore, by comparing the nine pairs of fertilization treatments, the relative increase in cumulative nitrous oxide-nitrogen (N_2O-N) emissions was found to be proportional to the relative increase in urea application, but independent of the amount of autumn-applied manure. These findings imply that N_2O emissions from fertilized agricultural soils in northeast China could be mitigated by supplying manure in the autumn and reducing the total amount of chemical N fertilizer applied in the following year. Although no significant difference in maize grain yield was found among the fertilization treatments, the grain yield-scaled N_2O emissions for the treatments with a lower chemical N application (e.g., N_<230>M_<15> and N_<200>M_<15> treatments) were significantly lower than those with a higher chemical N application (e.g., N_<320>M_<18> and N_<280>M_<18> treatments). Meanwhile, under the condition of the same application amount of chemical fertilizer N, the grain yield-scaled N_2O emission decreased with the increase of manure application rate. Thus, the results support the hypothesis that combining reductions in chemical N fertilizer and applying manure in autumn could be an effective strategy for mitigating N_2O emissions from N-fertilized soils in northeast China.
一般社団法人日本土壌肥料学会の論文

Mitigating nitrous oxide emissions from a maize-cropping black soil in northeast China by a combination of reducing chemical N fertilizer application and applying manure in autumn(Fertilizers and soil amendments)

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