Effect of different organic materials on specific surface areaand charge property of black soil colloid

Soil colloidal particles have high specific surface area and numerous reaction sites, which modify soil aggregate structures, contribute to soil-water erosion and are crucial for soil integrity. The principal scope of the wide use of organic amendments of various origins and natures in modern agriculture was to increase and/or restore organic matter contents in organically poor or depleted soils. This is needed to maintain and/or increase crop production and reduce soil exposure to degradation, erosion, desertification and pollution. Such amended soils could, however, be affected in different ways and at various degrees depending on the nature, origin and rate of amendments. Thus in this paper, a pot experiment was conducted to determine the effects of different organic materials on the colloidal properties and cation exchange capacity (CEC) of black soils. The results showed that colloidal properties and CEC of black soils varied with different organic materials. Compared with control treatment (CK), animal excrement decreased soil colloidal specific surface area (SSA) by 7.33%. The treatments of animal remnants, woody residues and herb residues increased soil colloidal SSA by 59.58%, 57.46% and 100.18%, respectively. At pH<6, similar surface negative charge load (Qv)-pH curves were noted in all the treatments. Application of organic materials resulted in higher contents of sample Qv (Qvs) than in CK at pH>6. Furthermore, Qv-pH curve of animal excrement treatment was similar to that of woody residues treatment. Also Qv contents of animal excrement and woody residues treatments were higher than that of CK and animal remnant, while animal remnant treatment Qv-pH curve was similar to that of CK. At pH 8~10, the order of Qvs content was animal excrement > woody residues > animal remnant > herb residues > CK. Whereas animal remnant and excrement reference fluid Qv (Qvr)-pH curves were similar, their Qvr contents were higher than that of CK and herb residues, Qvr-pH curve of CK was similar to that of herb residues treatment. The effects of different organic materials on CEC of black soils were also different. Animal excrement, animal remnant and woody residues significantly increased black soil CEC, while herb residues showed less effects.