Mulching effects on selected soil physical properties

The suitability of soil for sustaining plant growth and biological activity is a function of physical and chemical properties, many of which depend on the quantity and quality of soil organic matter. The equilibrium level of soil organic matter depends on the balance between input through plant residues and other biosolids and output through decomposition, erosion and leaching. However crop residues have numerous competing uses such as fodder, fuel and construction material. Similarly, costs are incurred in its application and these increase with mulch level. Therefore, it is necessary to establish optimum mulch application rates. Empirical data on soil organic matter in relation to input residue of residue are needed to understand management impact on soil quality. Long-term field plots were setup in 1989 to study the effects of mulching on soil physical properties of a Crosby silt loam (Aeric Ochraqualf or stagnic luvisol) soil in central Ohio. Treatments included mulch application at 0, 2, 4, 8 and 16 Mg ha−1 year−1 without crop cultivation. Soil samples from 0 to 10 cm depth were obtained in December 2000, 11 years after establishing the plots. The results demonstrated that mulch rates significantly increased available water capacity by 18–35%, total porosity by 35–46% and soil moisture retention at low suctions from 29 to 70%. At high suctions, no differences in soil moisture content were observed between mulch levels. Soil bulk density was not affected by mulch rate. High correlations were obtained between mulch rate and soil mean weight diameter (R2 = 0.87) and percent stable aggregates (R2 = 0.84). The study was able to determine optimum mulch rates of 4 Mg/ha for increased porosity and 8 Mg/ha for enhanced available water capacity, moisture retention and aggregate stability.