Comparison of hydraulic properties of soils mulched by different garden wastes

Abstract

【Background and Objective】 Organic mulch involves covering the soil surface with organic materials. While it has been recognized as an environmentally friendly method for reusing organic waste, improper mulching with organic wastes might degrade soil structure, hinder vegetation growth, and lead to environmental pollution. This paper is to investigate the alterations in soil hydraulic properties resulting from various garden waste mulches. 【Method】 The study is based on incubation. Garden wastes including grass clippings, tree leaves, tree branches, and branch-leaf mixtures are used to mulch the soil surface at a thickness ranging from 3 to 9 cm. The incubation lasts 21 months, after which we measure soil moisture content, bulk soil density, soil porosity, soil aeration, water holding capacity, and soil hydraulic conductivity. Their variations with the garden waste types and the mulching depth are analyzed. 【Result】 ① Mulching with all garden waste types increases soil hydraulic properties, albeit the improvement depends on the waste types and mulching thickness. ② Compared to without mulch, mulching reduces soil bulk density significantly by 5.6%-13.6%, increases the maximum soil water holding capacity by 31.9%-108.2%, capillary water holding capacity by 36.7%-114.2%, field water holding capacity by 64.1%-149.8%, and drainage capacity by 38.2%-67.1%. ③ Comprehensive evaluation reveals that those that were effective for improving hydraulic properties of soil are: 9 cm tree leaves, 9 cm grass clippings, 9 cm branch leaves, 6 cm grass clippings, mixture of 6 cm branch leaves and 9 cm tree branches. 【Conclusion】 Mulching soil with garden wastes can increase soil porosity and drainage capacity, thereby improving water-holding capacity of the soil. However, care needs to be taken in selecting waste types and mulching thicknesses in practical application in order to optimize mulching benefits.

Keywords

• waste
• mulches
• soil hydro-physical properties
• factor-analysis