不同施肥处理对黄泥田团聚体有机碳固持及其组分的影响

Long-term fertilization effects on soil aggregates organic carbon sequestration and distribution in a yellow-mud paddy soil

  • 摘要: 本文旨在研究长期不同施肥处理对南方黄泥田团聚体有机碳固持及其组分分配的影响, 为合理培肥及土壤碳库管理提供依据。基于始于1983年的在黄泥田进行的长期定位试验, 选择不施肥(CK)、单施化肥(NPK)、化肥+牛粪(NPKM)与化肥+全量稻秸还田(NPKS) 4个处理, 采集第36年各处理耕层土壤样品并分析各粒级团聚体有机碳固持及其组分变化。结果表明, 黄泥田耕层土壤以大团聚体(>2 mm)和中间团聚体(0.25~2 mm)为主, NPKM与NPKS处理的土壤大团聚体质量比重分别比CK显著增加22.0和15.5个百分点(P<0.05)。与CK相比, NPKM与NPKS处理中大团聚体对有机碳固持贡献率分别提高25.0和19.3个百分点(P<0.05)。施肥处理的大团聚体内轻组有机碳(LF-C)含量较CK显著增加, 其中NPKS处理后大团聚体中LF-C含量较CK增加32.3% (P<0.05)。大团聚体有机碳含量以及该团聚体内的LF-C含量与水稻产量和有机碳投入量都呈极显著正相关(P<0.01)。以上结果表明, 配施牛粪或秸秆还田有利于增加黄泥田大团聚体比例及其有机碳含量, 进而提高有机碳固持贡献率, 尤其是配施牛粪, 而且有机无机肥配施有利于提高大团聚体内轻组有机碳含量与固持贡献, 秸秆还田更为明显, 可为南方黄泥田施肥管理提供依据。

     

    Abstract: Agricultural management practices affect carbon sequestration in agricultural soils. This study was performed in southern China to investigate the effects of different fertilizations on soil aggregate organic carbon sequestration and distribution over time in yellow-mud paddy. There were four treatments: no fertilizer (CK), application of chemical fertilizer (NPK), combined application of chemical fertilizer and cattle manure (NPKM), and combined application of chemical fertilizer and straw (NPKS). After 36 years of the experiments (1983 to 2020), the soil samples were collected after rice harvest to analyze soil aggregate, organic carbon sequestration, and distribution. The results showed that macro-aggregates (>2 mm) and medium aggregates (0.25−2 mm) were major components of the bulk soil. Compared to CK, NPKM and NPKS significantly increased the proportions of macro-aggregates by 22.0% and 15.5%, respectively, but greatly decreased the proportions of medium aggregates (0.25−2 mm) by 14.3% and 10.2%, respectively (P<0.05). Application of fertilizer resulted in a significant increase in the organic carbon content of the bulk soil, ranging from 16.9% to 43.9%, compared with the CK treatment. The average organic carbon content of the macro-aggregates was 1.3–1.6 times that of the other aggregates. The organic carbon content of macro-aggregates (>2 mm), medium aggregates (0.25−2 mm), and silt and clay (<0.053 mm) was higher under NPKM than under CK. Furthermore, NPKS increased the organic carbon content of macro-aggregates (>2 mm) compared to CK. The macro-aggregate organic carbon content accounted for 44.5%−63.8% of the total soil organic carbon. Compared with CK, NPKM and NPKS treatments significantly enhanced macro-aggregate organic carbon sequestration by 25.0% and 19.3%, respectively; but decreased the organic carbon sequestration of medium aggregates (0.25−2 mm), micro-aggregates (0.053–0.25 mm), and silt and clay (<0.053 mm). For the macro-aggregates, the light fraction of organic carbon (LF-C) and mineral-associated organic matter (mSOC) were the major parts, and the proportions of mSOC accounted for 50.7%−57.7% of the macro-aggregates. Compared with CK, the content of LF-C increased by 20.7%−32.3% in the fertilization treatments, respectively, and the contribution of LF-C to total soil organic carbon was most significantly increased by 8.9% and 9.4% under the NPKM and NPKS treatments (P<0.05), respectively. For the medium aggregates, the organic carbon content of the fine fraction organic carbon was significantly higher under NPKM treatment than under other treatments (P<0.05); other sub-fractions was not affected by the application of fertilizer. The coarse fraction of organic carbon (CF-C) and mSOC were the major components of the organic carbon in medium aggregates. NPKM and NPKS significantly decreased the sequestration of LF-C, CF-C, and mSOC in medium aggregates compared with the NPK and CK treatments (P<0.05). The organic carbon content of the bulk soil was found to be significantly correlated with rice yield and organic input (P<0.01). Both macro-aggregate organic carbon content and LF-C content showed a significant positive correlation with rice yield (P<0.01). They were also significantly positively correlated with the organic carbon input (P<0.01). Overall, the combined application of chemical fertilizer with cattle mature or straw could increase the proportions and content of organic carbon of macro-aggregates, thus promoting the contribution of total soil organic carbon, especially with the application of cattle manure. Additionally, the combined application of chemical fertilizer and straw was beneficial in promoting macro-aggregate LF-C content and the contribution of total soil organic carbon. The organic carbon content and fractions of active carbon in macro-aggregates are closely related to the productivity of yellow-mud paddy soil. The results provide methods for fertilization management of yellow-mud paddy soil in southern China.