肥料减施条件下水稻土壤有机碳组分对紫云英—稻草协同利用的响应

研究紫云英与稻草不同利用模式在化肥减量条件下稻田表层土壤有机碳及其活性组分的差异,为合理利用有机物料调控土壤肥力提供参考。采用湖南省南县连续5年(2011—2015年)大田定位试验的方法,研究了减量施肥下洞庭湖地区紫潮泥双季稻田0-20cm表层土壤总有机碳(TOC)、微生物量碳(MBC)、可溶性有机碳(DOC)、易氧化有机碳(EOC)和轻组有机碳(LFOC)对紫云英与稻草不同利用模式的响应。结果表明:与不施肥(CK)相比,单施化肥(F100)TOC、MBC、DOC、EOC和LFOC的含量均有显著上升,增幅分别为12.2%,19.5%,18.6%,11.3%和100.9%。化肥减量20%条件下紫云英与稻草利用模式更有助于有机碳组分的积累,其中晚稻留高桩还田冬种紫云英(F80+HR+A)处理效果最为突出,与CK相比,增幅分别为18.3%,47.2%,24.1%,20.0%和204.0%。减量施肥下紫云英单独利用相比稻草单独还田更益于MBC、DOC与EOC的积累,增幅分别为9.8%,4.0%和0.6%,土壤LFOC则相反,下降了34.8%。敏感指数分析表明土壤有机碳及其活性组分中LFOC对土壤质量变化最为敏感,其次是MBC,二者可作为衡量土壤质量状况的良好指标。F80+HR+A各有机碳组分敏感性均显著高于F100处理。相关性分析表明水稻产量、土壤有机碳及其组分之间均呈极显著相关(p0.01)。综上所述,化肥减量条件下不同紫云英与稻草利用模式对紫潮泥稻田土壤有机碳及其活性组分含量的影响存在明显差异,稻草还田能够显著提高土壤总有机碳和轻组有机碳的含量,紫云英的利用则有利于土壤微生物量碳、可溶性有机碳和易氧化有机碳的积累,而紫云英与稻草协同利用模式,尤其是晚稻留高桩还田冬种紫云英更有助于土壤有机碳及其活性组分的积累。

Responses of Contents of Soil Organic Carbon Fractions to Chinese Milkvetch-rice straw Synergistic Dispatching under the Condition of Reducing Fertilizer Application

Effects of different utilization models of Chinese milk vetch and rice straw on characteristics of paddy soil organic carbon fractions under chemical fertilizer reduction were studied in order to provide a reference for rational utilization of organic materials for soil fertility control.A field experiment for five consecutive years (during 2011-2015) was designed to study the responses of the contents of purple soil total organic carbon (TOC),microbial biomass carbon (MBC),dissolved organic carbon (DOC),easily-oxidized organic carbon (EOC) and light fraction organic carbon (LFOC) to different utilization models of Chinese milk vetch and rice straw in double-rice cropping field of the Dongting Lake region in Nan Country of Hunan Province.The results indicated that F100 significantly increased the contents of soil TOC,MBC,DOC,EOC and LFOC,which was 12.2％,19.5％,18.6％,11.3％ and 100.9％ greater than that of the unfertilized control,respectively.Compared with F100,different utilization models of Chinese milk vetch and rice straw could be more suitable for the accumulation of TOC,MBC,DOC,EOC and LFOC under chemical fertilizer reduction.Wherein the optimal was F80+HR+A,which was 18.3％,47.2％,24.1％,20.0％ and 204.0％ greater than that of the unfertilized control,respectively.Applying Chinese milk vetch alone under chemical fertilizer reduction favored the buildup of MBC,DOC and EOC,which was 9.8％,4.0％ and 0.6％ greater than that of rice straw alone,respectively,but the LFOC was the opposite,being 34.8％ lower.Sensitive index showed that the LFOC and MBC had high activity,LFOC was more labile than MBC,and they could be used to evaluate soil quality.The sensitive indices of all organic carbon fractions in F80+ HR+A were significantly higher than those of F100.Correlation analysis showed that there was a significant relationship among rice yield,TOC and its labile organic carbon fractions (p ＜ 0.01).In conclusion,there were significant differences in TOC,labile organic carbon fractions among treatments amended with Chinese milk vetch and rice straw under chemical fertilizer reduction in purple soil.Returning rice straw could be prone to increase TOC and LFOC pool,and application of Chinese milk vetch was favorable to promote MBC,DOC and EOC.The pattern of Chinese milk vetch-rice straw synergistic dispatching,especially returning high pile of straw and winter planting Chinese milk vetch,could be prone to increase TOC and labile organic carbon fractions.