长期施肥对水稻根系有机酸分泌和土壤有机碳组分的影响

本研究以江西省红壤研究所水稻土长期定位试验田(始于1981年)为对象,分析了不施肥(CK)、单施化肥(NPK)、有机无机配施(NPKM)3种施肥措施对水稻根系有机酸分泌速率及土壤有机碳组分的影响。结果表明:NPK和NPKM处理水稻根系分泌有机酸总量均显著高于CK处理(P0.05,下同),其中NPKM处理最高,提高了54.78%;相对于CK处理,NPK处理水稻根系酒石酸分泌速率显著增加,提高了82.63%,NPKM处理的草酸与苹果酸分泌速率显著增加,分别增加了69.93%、110.98%,而NPK和NPKM处理的柠檬酸分泌速率分别降低了36.57%与40.57%。与CK处理相比,NPKM处理土壤有机碳、颗粒有机碳、微生物生物量碳与可溶性有机碳均显著增加,而NPK处理却无显著变化;可溶性有机碳结构的进一步分析表明,NPKM处理促进了可溶性有机碳中类胡敏酸和类富里酸物质的累积,在可溶性有机碳中所占比例分别为31%、44%,NPK处理可溶性有机碳结构无明显变化;CK和NPK处理中可溶性有机碳的有机物来源主要是植物与微生物的混合源,而NPKM处理主要是微生物代谢所分泌的产物。

Effects of Long-term Fertilization on Organic Acids in Root Exudates and SOC Components of Red Paddy Soils

Based on the long-term fertilization experiment conducted since 1981 in red paddy soil in the Red Soil Institute of Jiangxi Province, China, the effects of different fertilization treatments, including no fertilizer (CK), chemical fertilizer only (NPK), chemical fertilizer plus organic manures (NPKM) were studied on the secreting rates of organic acids in rice root exudates and on SOC components. Results showed that NPK and NPKM treatments increased total organic acid contents in the root exudates compared with CK treatment (P<0.05, the below is same). Compared with treatment of CK, NPK treatment significantly increased the secreting rate of tartaric acid by 82.63%, NPKM treatment significantly increased oxalic acid and malic acid by 69.93% and 110.98%, respectively; however, NPK and NPKM treatments significantly decreased citric acid secreting rates by 36.57% and 40.57%, respectively. Compared with CK, NPKM treatment significantly increased the contents of soil organic carbon (SOC), particulate organic carbon (POC), microbial biomass organic carbon (MBC) and dissolved organic carbon (DOC), while NPK treatments influenced these components insignificantly. NPKM treatment also promoted the accumulation of humic acid-like and fulvic acid-like materials, which constituted 31% and 44% of DOC, respectively; whereas NPK treatment changed DOC components little. The organic matters of DOC were botanically and microbially derived in CK and NPK treatments, while they were resulted from the processes such as extracellular release and microorganism excretion in NPKM treatment.