长期不同施肥下红壤活性有机质与碳库管理指数变化

LABILE ORGANIC MATTER AND CARBON MANAGEMENT INDEX IN RED SOIL UNDER LONG-TERM FERTILIZATION

对长期不同施肥5 a和10 a后红壤活性有机质进行了测定,结果表明,耕作10 a不施肥或仅施化肥(CK、N、NP、NK、PK、NPK)的土壤活性有机质(LOM)及碳库管理指数(CMI)都明显下降,最大下降(CK)分别为40.5%和48.1;而有机肥或有机肥化肥配合施用(M、MNPK、1.5MNPK),LOM和CMI则显著升高,最大升高(1.5MNPK)分别为183%和195;秸秆还田(SNPK)处理LOM和CMI先下降后增加,5 a分别下降25.2%和31,10 a又分别上升17.9%和13。说明化肥主要提高非活性有机质,有机肥则显著改善土壤有机质质量,秸秆还田对提高红壤有机质质量比有机肥慢。用33 mmol L-1、167 mmol L-13、33 mmol L-1KMnO4测定的三种活性有机质(本文分别称其为高活性有机质HLOM、中活性有机质MLOM和活性有机质LOM)的含量依次增加,分别占总有机质的5.6%、9.6%和14.5%。三种活性有机质之间呈显著或极显著相关,HLOM与MLOM相关系数为0.478*,HLOM与LOM为0.592**,MLOM与LOM为0.716**。作物产量只与MLOM和LOM极显著相关,相关系数分别为0.821**和0.602**,而和总有机质没有显著的相关性。同时,LOM及CMI与土壤阳离子交换量、交换性钾、交换性钙、盐基总量、微量元素等呈显著或极显著正相关,但总有机质与上述土壤化学指标相关性差。这些结果暗示LOM和CMI比总有机质更能客观反映土壤肥力和土壤质量的变化情况,应该成为描述土壤质量和评价土壤管理的良好指标。

Labile organic matter （LOM） in red soil under long-term fertilization was measured using the KMnO4 oxidation method. The results show that LOM and carbon management index （CMI） decreased apparently in red soils in Treatment Zerofertilizer （CK） or treatments applied chemical fertilizer （CK, N, NP, NK, PK, and NPK） after 10 years of cultivation, with the maximum drop （CK） by 40.5 % in LOM and 48.1 in CMI; but increased significantly in the treatments applied with manure or with both manure and chemical fertilizers （M, MNPK, and 1.SMNPK）, with the maximum rise （1.SMNPK） by 183 % in LOM and 195 in CMI. LOM and CMI in Treatment SNPK decreased after 5 years by 25.2% and 31, respectively; but increased after 10 years by 17.9% and 13, respectively. These suggest that chemical fertilizers mainly increase non-labile organic matter content, while manure mainly improves quality of soil organic matter, and straws are slower in the effect than manure. The contents of three fractions of labile organic matter named as highly labile organic matter （ HLOM）, mid-labile organic matter （MLOM） and labile organic matter （LOM）, respectively, were determined using 33 mmol L^-1, 167 mmol L^-1 and 333 mmol L^- 1KMnO4, respectively. Averagely, HLOM, MLOM and LOM accounted for 5.6%, 9.6% and 14.5 % of total organic matter, respectively. Significant correlations were found among the three with the coefficient between HLOM and MLOM being 0.478 ^＊, between HLOM and LOM being 0.592^＊＊, and between MLOM and LOM being 0.716^＊＊. Crop yield was also found closely related to MLOM and LOM, with the correlation coefficient being 0.821^＊＊ and 0.602^＊＊ , respectively, but the correlation between crop yield and total organic matter was insignificant. At the same time, LOM and CMI showed significant positive correlations with cation exchange capacity （CEC）, exchangeable potassium, exchangeable calcium, total base and microelement, etc.. However, total organic matter was insignificantly related to those chemical indexes. So, LOM and CMI could more than total organic matter objectively reflect changes in soil fertility and soil quality, and should be used as indices to describe soil quality and assess soil management.