有机肥替代下华南地区粮蔬轮作模式N2O排放特征

Characteristics of nitrous oxide emissions in crop and vegetable rotation pattern in South China Region under organic fertilizer substitution

  • 摘要: 为探索有机肥替代措施在华南地区气候湿热多雨、土壤酸化和复种指数极高情况下的土壤N2O排放特征及其关键影响因素, 本研究利用静态暗箱-气相色谱法, 以“菜心(P1)-生菜(P2)-甜玉米(P3)-菜心(P4)”轮作农田土壤为研究对象, 进行周年原位观测(2022年12月3日—2023年12月1日)。试验设置5个处理, 即不施氮肥处理(CK)、化肥施用处理(R)、商品有机肥替代15%化肥氮处理(M15%)、商品有机肥替代30%化肥氮处理(M30%)和尾菜堆肥替代15%化肥氮处理(S15%)。结果表明: 各有机肥替代处理作物产量与R处理间无显著差异。各处理N2O排放通量为6.52~2 441.42 μg(N2O)∙m−2 h−1, 施氮处理N2O排放峰值一般在施肥伴随灌溉后2~5 d内出现。R处理N2O周年排放总量为2.66 kg(N)∙hm−2, M15%处理与R处理间无显著差异, M30%和S15%处理N2O周年排放总量比R处理分别显著增加52.25%和38.72% (P<0.05)。N2O排放主要来自作物生长季, R处理P1、P2、P3、P4和休闲期N2O排放总量分别占周年排放总量的8.30%、11.32%、46.79%、13.21%和20.38%, 有机肥替代化肥氮对N2O排放总量的影响在不同作物生长季有所差异。结构方程模型表明, 环境因素中, N2O排放通量受土壤温度影响最大(P<0.001), 土壤孔隙含水量、土壤NH4+-N含量和NO3-N含量对N2O排放通量影响不显著; 干湿交替过程促进了甜玉米季N2O排放。根据1年试验结果, 华南地区粮蔬轮作种植模式下, 建议在蔬菜季采用有机肥替代化肥措施; 从产量和N2O周年排放总量角度来看, 推荐商品有机肥替代15%化肥氮措施。

     

    Abstract: The aim of this study was to explore nitrous oxide (N2O) emissions and key impact factors under alternative organic fertilizer substitution management in South China in the context of the regional conditions (hot and rainy climate, acidic soils) and high multiple cropping index cultivation. We conducted one-year in situ observations (from December 3 in 2022 to December 1 in 2023) using the static opaque chamber method. Chinese flowering cabbage season (P1), lettuce season (P2), sweet corn season (P3), and Chinese flowering cabbage season (P4) were cultivated in turn in this study. Five treatments were implemented: no nitrogen fertilizer application (CK), chemical fertilizer application (R), substitution 15% and 30% chemical fertilizer nitrogen with commercial organic fertilizer (M15% and M30%), and substitution 15% of chemical fertilizer nitrogen with composted vegetable residue (S15%). Compared to R treatment, there was no significant difference in crop yield under the organic fertilizer replacement treatments. During the whole observation period, the N2O emission fluxes of each treatment ranged from 6.52 to 2 441.42 μg(N2O)∙m−2∙h−1, and the N2O peaks of each nitrogen application treatment generally occurred within 2−5 d following the fertilization and irrigation events. The annual N2O emission under R treatment was 2.66 kg(N)∙hm−2, there was no significant difference between M15% and R treatment. However, compared to R treatment, the annual N2O emission under M30% and S15% treatment increased by 52.25% and 38.72% (P<0.05), respectively. Under the R treatment, the N2O emissions of P1, P2, P3, P4, and the leisure period accounted for 8.30%, 11.32%, 46.79%, 13.21%, and 20.38% of the annual emissions, respectively. The effects of substituting chemical fertilizer with organic fertilizer on N2O emissions varied among the different crop seasons. The structural equation model revealed that soil temperature showed the greatest contribution to N2O emissions (P<0.001), while the effects of water filled pore space (WFPS), soil NO3-N content and NH4+-N content on N2O emissions were not significant. Based on one-year observations, we recommend organic fertilizer substitution management applied during vegetable growing seasons under crop and vegetable rotation pattern in South China. Considering both crop yield and annual N2O emissions, we suggest substituting 15% of chemical fertilizer nitrogen with commercial organic fertilizer.

     

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