长期施肥对西南黄壤有机碳平衡的影响

Effects of Long-term Fertilization on Soil Organic Carbon Balance in a Yellow Soil of South Western China

为阐明长期施肥对西南地区黄壤有机碳变化特征的影响,探讨土壤可持续利用培肥模式,从1995年起采用10种施肥模式(CK、1/4 M+3/4 NPK、1/2 M+1/2 NPK、M、NPKM、NPK、NK、N、NP、PK)对贵阳市小河区玉米地黄壤进行处理,分析了各施肥模式下土壤有机碳的变化特征及其与作物产量之间的动态变化关系。结果表明,随着施有机肥年限延长,土壤有机碳总体呈增加趋势,而施化肥表现出下降趋势,无机肥配施对提高土壤有机碳含量作用明显。不同施肥模式有机碳平衡变化很大,施有机肥,土壤有机碳平衡量均为正值,有机肥施用量的增加也会导致土壤有机碳含量提高;不施肥和施用化肥处理的有机碳平衡量均为负值,各施氮处理(NPK、NK、N、NP)间有机碳平衡量差异不显著(p值为0.08),但与不施氮处理(PK)的有机碳平衡量存在差异显著(p<0.01)。黄壤有机碳平衡量与系统总碳投入之间呈现显著的正相关关系(R2=0.9995),维持黄壤有机碳平衡所需的最低碳投入量为每年2.57 t hm-2。施有机肥处理中,玉米产量与有机碳含量表现出较好的正相关关系(R2均大于0.6);而不施肥或施用化肥处理中,二者的相关性较差(R2均小于0.3)。以上结果说明,研究区黄壤中有机碳还没饱和,仍具一定的固碳潜力,施有机肥,尤其是有机肥与化肥配施可以提高土壤有机碳含量。

To estimate the effect of long-term fertilization on variation of soil organic carbon and discuss fertility maintaining mode for sustainable land use, the yellow soil with 10 fertilization treatments(CK, 1/4M + 3/4NPK, 1/2M + 1/2NPK, M, NPKM, NPK, NK, N, NP, PK) from 1994 to 2011were collected to determine soil organic carbon contents. Results showed that the soil organic carbon first decreased then increased in the study years except for the overall decreased trend in the treatments of chemical fertilizer. In the MNPK treatment, the soil organic carbon content increased continuously. Soil organic content varied among different treatments, in which positive values were observed in the treatments of 1/4M + 3/4NPK, 1/2M + 1/2NPK, M and MNPK, while negative value was observed in other treatments. Significant difference was observed between nitrogen treatments(NPK, NK, N, NP) and without nitrogen(PK) treatment. Positive linear correlation was observed between soil organic carbon at steady state and carbon input. The lowest amount of carbon input on maintaining the yellow soil organic carbon balance was 2.57 t hm-2a-1. There was a positive linear correlation between maize yield and soil organic carbon in manure treatments. No correlation between maize yield and soil organic carbon however, was observed in chemical treatments. The results suggested that organic carbon in yellow soil was not in saturated state which had the potential to sequester more carbon. Manure fertilizer application especially the combination of manure and chemical fertilizer could increase soil organic carbon.