长期施肥处理下不同类型水稻土有机碳矿化的动态差异

Dynamic Differences of Organic Carbon Mineralization in Different Types of Paddy Soil Under Long-Term Located Fertilization

【目的】研究田间长期定位施肥处理下不同类型水稻土有机碳矿化的动态差异及其影响因素,为揭示不同类型水稻土有机碳的循环特征及制定合理的养分管理措施等提供依据。【方法】以江苏常熟(乌栅土)、江西余江(低肥力红壤)、湖南望城(高肥力红壤)和重庆(紫色土)4个地点长期定位施肥试验的水稻土为研究对象,选择不施肥(CK)、单施化肥(NPK)和化肥配合秸秆还田(NPKS)3个处理,通过室内27 d的有机碳矿化培养试验,采用室内恒温培养、碱液吸收法测定土壤有机碳的矿化量;选择Jones一级动力学方程拟合土壤有机碳累积矿化量的动态变化,比较土壤类型和长期不同施肥处理对有机碳矿化动态的影响。【结果】长期施肥处理可以提高土壤全量养分(全氮、全磷、全钾)和有机碳含量,但会降低土壤p H。长期施肥可以显著提高土壤有机碳累积矿化量(C)(常熟试验点除外),不同施肥处理下增加幅度为11.7%—86.1%,而对于矿化动力学方程拟合所得土壤潜在可矿化有机碳量(C0)、易矿化有机碳量(C1),只有同为红壤的余江和望城两地的施肥处理可以显著提高。相同施肥处理下C、C0和C1均表现为常熟、望城试验点的较大,重庆、余江试验点的较小,而潜在可矿化有机碳量与土壤有机碳的比值(C0/SOC)则是余江试验点较大;相关性分析发现有机碳、总氮、碱解氮、全磷与C、C0和C1呈极显著正相关(P<0.01),p H和全钾与C呈极显著负相关,而C0/SOC与有机碳、p H和各养分指标均呈显著或极显著负相关。对于矿化速率常数(k),施肥处理对其影响并不显著,但不同土壤类型可以显著影响k。相关性分析表明k与p H、C/N和全钾呈极显著负相关(P<0.01),与速效钾呈显著负相关(P<0.05)。通过聚合推进树(ABT)方法分析了不同因子的相对影响,结果表明碱解氮和有机碳含量对C和C0影响较大,相对贡献率分别为23.8%、20.2%(对于C)和29.5%、23.7%(对于C0);有机碳含量和p H对C1和C0/SOC影响最大,相对贡献率分别为26.7%、15.9%(对于C1)和34.4%、23.0%(对于C0/SOC);p H和全钾对k的影响最大,相对贡献率分别为34.2%和22.1%。【结论】土壤类型对有机碳矿化动态的影响要大于长期施肥措施产生的影响,不同地点长期定位施肥处理下土壤母质、p H、有机碳含量和养分含量等土壤性质的不同,造成了土壤有机碳矿化的动态差异。

【Objective】The objective of this study is to explore dynamic differences and influence factors of organic carbon mineralization in different types of paddy soil under long-term located fertilization. The results could help us to illuminate the characteristics of organic carbon mineralization in different types of paddy soil and provide guidance for formulating reasonable nutrient management measures.【Method】In this study, the paddy soils in four different places were used, including Changshu（gleyed soils） in Jiangsu province, Yujiang（reddish soil of low fertility） in Jiangxi province, Wangcheng（reddish soil of high fertility） in Hunan province, and Chongqing（purple soil）. The soils were collected in long-term fertilization location including three different treatments, as control（no fertilizer, CK）, N, P and K fertilizer（NPK）, N, P and K fertilizer plus rice straw（NPKS）. The organic carbon mineralization laboratory incubation experiment was conducted in 27 days. The cumulative carbon mineralization was measured through alkali absorption method in constant incubator. The Jones first-order kinetic model was used to express the dynamics of cumulative carbon mineralization with respect to incubation time and was fitted to compare the influence of soil type and different applications of long-term fertilization on the dynamics of carbon mineralization.【Result】Long-term fertilization could improve the content of soil total N, P, K and organic carbon but decreased the soil p H. Long-term fertilization could significantly improve the cumulative carbon mineralization（C） except Changshu soil and different fertilizations caused the increase of 11.7%-86.1%. Two parameters in mineralization kinetic equation, potential mineralization of organic carbon（C0） and easy mineralization of organic carbon（C1）, could be significantly improved by fertilization in the reddish paddy soil of Yujiang and Wangcheng. In the same fertilization treatment, C, C0 and C1 were bigger in Changshu and Wangcheng while smaller in Chongqing and Yujiang; Ratio of C0 to soil organic carbon（C0/SOC） was bigger in Yujiang. Correlation analysis indicated that soil organic carbon, total nitrogen, available nitrogen and total phosphorus showed a very significant positive correlation with C, C0 and C1（P〈0.01）; p H and total potassium showed a very significant negative correlation with C; C0/SOC showed a significant negative correlation with SOC, p H and all nutrient indexes. The fertilization treatments had no significant effect on mineralization rate constant（k） while the soil type affected k significantly. The k displayed a very significant negative correlation with p H, C/N, total K（P〈0.01） and a significant negative correlation with available K（P〈0.05）. The relative influence of different parameters was obtained through aggregated boosted trees and the result showed that available nitrogen and soil organic carbon had a bigger impact on C and C0 with relative influence at 23.8%, 20.2%（for C） and 29.5%, 23.7%（for C0）; soil organic carbon and p H had a bigger impact on C1 and C0/SOC with relative influence at 26.7%, 15.9%（for C1） and 34.4%, 23.0% for（C0/SOC）; p H and total potassium had a bigger impact on mineralization rate constant（k） with relative influence at 34.2% and 22.1%, respectively.【Conclusion】The type of soil exerted a bigger impact on soil organic carbon mineralization dynamic than long-term located fertilization. The difference of parent material, p H, organic carbon and nutrient content of soil in different long-term fertilization locations account for the dynamic difference of organic carbon mineralization.