Evaluating the Effects of Compost, Vermicompost, and Biochar on Physical Quality of Sandy-Loam Soils

Improving the physical quality of coarse-textured soils by organic amendments requires choosing the amendment and the dose. The effects of different doses of compost, vermicompost, and biochar on soil bulk density (BD) and water retention parameters (macroporosity, PMAC; aeration capacity, AC; plant available water capacity, PAWC; relative field capacity, RFC) were tested for two sandy-loam soils. Without any treatment, these soils had too high BD and AC values and too low PMAC, PAWC, and RFC values. No amendment satisfactorily improved the PMAC. Only the biochar yielded statistically significant relationships between the BD, AC, PAWC, and RFC, and the amendment rate, ar. With this amendment, aeration and water storage improved because soil water content at field capacity increased with an ar more than those at saturation and the permanent wilting point. A dose of biochar (50 t/ha in a 5-cm-thick layer) made the soil physical quality good with reference to all considered parameters was identified. A single application of a rather high amount of biochar can be expected to improve the physical quality of coarse-textured soils for a long time. The general validity of the optimal ranges of values for the considered parameters and the time dependence of amendment effects in the field require further check.