施肥和秸秆还田对红壤水稻土有机碳分布变异及其矿化特性的影响

摘要

利用始于1990年的湖南桃园红壤水稻土长期定位试验,研究了长期施肥和秸秆还田对红壤水稻土剖面有机碳含量和δ13C值分布,有机碳密度和变异幅度,以及有机碳矿化特性的影响.结果表明,长期施肥和秸秆还田使红壤稻田土壤表层有机碳含量显著升高,秸秆还田对有机质的累积作用明显优于仅施化肥处理.施肥或秸秆还田使0～25 cm和0～ 50 cm土层的有机碳密度均明显提高,且有机碳变异幅度也明显增大.0～10cm表层土壤δ13C值与对照的差异最大,而施化肥或秸秆还田处理之间的差异不大.各施肥处理土壤有机碳在培养初期的矿化速率较大,并在1～3周内迅速降低且逐渐达到稳定状态.秸秆还田使各处理有机碳矿化速率的提高较明显,各处理的平均矿化速率为CO247.75～31.16 ml/(kg.d),稳定矿化速率为CO240～60ml/(kg·d),12周培养期内累积矿化量大小为CK+C＞NP+C＞N+C＞NPK+C＞NP＞NPK＞N＞NK＞CK.长期施化肥和秸秆还田,均使土壤有机碳的累积矿化量提高,而秸秆还田作用更明显.因此,长期施肥和秸秆还田作为土壤有机碳累积的途径,有利于提高红壤水稻土的养分供应能力,并且能够维持稻田生态系统有机碳库的缓冲性和长期稳定性.%Based on a long-term fertilization experiment of paddy field setup in 1990 and located in Taoyuan County of Hunan Province, the effects of fertilization and straw returning on soil organic carbon (SOC) distribution over soil depth, density and variation, stable carbon isotope natural abundance (δ13C), and mineralization characteristics of organic carbon were studied. Results showed that long-term amendments of fertilizer and crop straw returning significantly increased SOC in the top soil, straw returning were better than chemical fertilizer in organic carbon accumulation; SOC density of chemical fertilizer and crop straw treatments in 0 - 25 cm and 0 - 50 cm were significantly increased, but variation range of SOC density was also increased with long-term amendments; Significant differences of the δI3C with CK were found in 0 -10 cm soil layer, but no significant differences among chemical fertilizer treatments and crop straw treatments; Organic carbon mineralization of different treatments reached the peak in the initial stage, and gradually leveled off and stable in I - 3 weeks followed; The average mineralization rates varied in the range of 47.75 - 31.16 CO2 ml/(kgd)and stable mineralization rates in the range of 40 - 60 CO2ml/(kg·d), cumulative mineralization amounts of different treatments in 12 weeks were in the decreasing order of CK+C>NP+C>N+C>NPK+C>NP>NPK>N>NK>CK; Amendments of fertilizer and crop straws increased SOC cumulative mineralization, but the effects of crop straws returning were more significant than chemical fertilizer; Therefore, as a way of SOC accumulation long-term amendments of chemical fertilizer and crop straws improved supplying capability of soil nutrient, and benefited for buffering and stabilizing organic carbon pool in paddy soil ecosystem.