Response of Soil Macro and Micro-aggregates and Dispersion Ratio to Solid Cattle Manure in Cultivated and Non- cultivated Soils

Abstract

Manure application is important for maintaining and improving soil quality and aggregation.  Two field experiments were carried out on a silty clay loam soil during the two successive summer seasons of 2016 and 2017 to examine the influence of solid cattle manure (SCM) on soil macro and micro-aggregates (Large soil macro-aggregates ˃2 mm, small macro-aggregates 0.25- 2 mm and soil micro-aggregates < 0.053- 0.25 mm) and dispersion ratio in cultivated and non- cultivated soil. The first was designed to study the effect of SCM on soil aggregation (non- cultivated soil), and the second was to study the effect of SCM added to the grown potato on soil aggregation (cultivated soil).  Four rates of SCM were added to the soil before tilth: 0, 12, 24 and 36 Mg ha-1. The SCM application significantly (P < 0.05) affected soil physical properties after 2 years application. Soil porosity and saturated hydraulic conductivity increased, while bulk density decreased due to increasing aggregation in the non-cultivated soil compared to the cultivated one. The aggregates large soil macro-aggregates, small macro-aggregates and soil micro-aggregates significantly (P < 0.05) increased by the application of SCM. The application of SCM decreased significantly the dispersion ratio. The SCM increased significantly the structure coefficient in the non- cultivated compared to the cultivated soil. The SCM has a major direct effect on soil macro and micro-aggregates under potato production, particularly at high rates of SCM. The organic matter showed highly significant positive correlations with macro and micro-aggregates and highly negative one with dispersion ratio. The strong positive correlation was between the number of tubers and dispersion ratio, as well as between potato yield and soil aggregation, which indicated that the organic matter addition increased the potato yield and decreased the dispersion ratio. In conclusion, the SCM improved soil aggregation and dispersion ratio in cultivated and non- cultivated soils with increase potato yield.