To develop an evaluation index system for soil environment of paddy fields with combined application of organic fertilizers, the present study employed meta-analysis to selected sensitive factors of the soil environment. The identified factors were used to construct an index system for soil environment of combined application of organic fertilizers in paddy fields through coupling of the variation analysis, correlation analysis, principal component analysis, and random forest. Of 43 soil environment factors, meta-analysis identified 26 sensitive factors: soil bulk density(BD), non-capillary porosity, aggregates(>5, 2~5, 1~2, 0.5~1, and 0.25~0.5 mm), < 0.25 mm microaggregates, pH, electrical conductivity(EC), exchangeable potassium ions, organic carbon(SOC), total nitrogen(TN), total phosphorus(TP), total potassium(TK), available nitrogen(AN), available phosphorus(AP), available potassium(AK), soil microbial biomass carbon(MBC), soil microbial biomass nitrogen(MBN), soil urease(SUE)activity, soil invertase(SSC)activity, soil dehydrogenase(SDH)activity, zinc(Zn), copper(Cu), and cadmium(Cd). The environmental sensitive factors with a cumulative contribution rate greater than 85% were selected by variation analysis. The integrated analysis of the results of the correlation analysis, principal component analysis, and random forest of the selected sensitive factors was utilized to construct the index system for soil environmental effects of combined application of organic fertilizers in paddy fields. The system was based on BD, pH, EC, SOC, TN, AK, AP, MBC, Cd, and Cu. The results of the present study provide a basis for the evaluation of soil environmental effects of combined organic fertilizer application in paddy fields, and offer a new concept for the construction of a soil environmental assessment index system. |