Effect of organic residues on soil properties of loamy topsoil of haplic Luvisol in Northern Germany

The application of organic residues should ensure a sufficient air capacity (AC) and plant available water capacity (AWC) to improve the soil aeration and water supply for plant roots, whereas the air permeability (k_a) primarily depends on the number of functional and, therefore, connected pores. The objective of the study was to investigate the effect of digestates derived from maize (Zea mays L.), sugar beet (Beta vulgaris L.), and wheat (Triticum aestivum L.) in ratios of 100%, 80%, and 20%, respectively; compost of shrub debris; and sewage sludge on AC, AWC, and k_a values, including the pore continuity indices (c₂, c₃) of a loamy Ap horizon of a haplic Luvisol. The results indicate that AC values increase from 0.142 of up to 0.191 cm³ cm⁻³, but pore continuities and AWC values decrease from 0.143 down to 0.111 cm³ cm⁻³, except for wheat-containing digestate (20w80b), which shows an opposite trend. The application of organic residues can compensate low AC values but not the AWC values. The wheat-containing digestate should be preferred for improving the water-holding capacity and, therefore, the water supply for plant roots.