有机肥对酸性稻田土壤Cd赋存形态的影响途径和机制

以堆肥后的菜籽饼为有机肥,通过水稻田间试验,研究了有机肥对土壤有机质(OM)、pH、微生物量碳、氮(MBC、MBN)、3种酶活性(酸性磷酸酶,ACP、脲酶,UA、脱氢酶,DH)及土壤Cd的赋存形态的影响,利用通径分析研究了有机肥对土壤Cd赋存形态的影响途径和机制。结果表明:(1)施用有机肥能显著提高土壤OM含量和土壤pH,显著增加土壤中可还原态Cd(Red-Cd)和可氧化态Cd(Oxi-Cd)含量,降低土壤酸可提取态Cd(Aci-Cd)含量。(2)施用有机肥能不同程度增加土壤ACP、UA及DH活性,提高土壤MBC和MBN含量。(3)通径分析结果表明,施用有机肥降低土壤Aci-Cd含量主要是通过提高土壤OM含量、DH活性和MBC含量这3个途径完成。土壤OM含量、土壤DH活性和MBC含量的决策系数分别为0.846,0.257,-0.276,均达到显著水平,是有机肥施用下影响土壤Aci-Cd含量的主控因子。

Mechanisms and Influence Approaches of Organic Fertilizer on Occurrence Mode of Cd in Acid Paddy Soil

A field experimental were conducted in acid paddy soil to study the influence of the fermented rapeseed residue as an organic fertilizer on soil organic matter (OM), pH value, microbial biomass carbon and nitrogen (MBC and MBN), three enzymes (acid phosphatase, ACP, urease, UA, and dehydrogenase, DH), and occurrence mode of Cd in soil. Path analysis was used to study the influence approaches and mechanisms of organic fertilizer application on soil Cd occurrence mode. The results showed that:(1) The application of organic fertilizer could significantly increase the OM content, alleviate soil acidity, significantly increase the concentrations of reducible Cd (Red-Cd) and oxidizable-Cd, and decrease the concentrations of acid extractable-Cd (Aci-Cd) in soil. (2) ACP, UA and DH activities and MBC and MBN concentrations in soil were showed gradually raised after organic fertilizer application. (3) Path analysis results showed that the reduction of Aci-Cd concentrations in soil after organic fertilizer application was mainly achieved by increasing of OM content, DH activity, and MBC concentrations in soil. The decision coefficients of soil OM content, soil DH activity, and MBC content were 0.846, 0.257 and -0.276, respectively, which reached the significant levels and suggested they are the main controlling factors of soil Aci-Cd content under organic fertilizer application.