Effects of co-composted maize, sewage sludge, and biochar mixtures on hydrological and physical qualities of sandy soil

The agronomic utilization of compost has some benefits to soil. Compost increase soil nutrients, and soil organic matter content; thus, it has a positive effect on biological, physical, and chemical properties of the soil. During the composting process, different feedstocks such as plant wastes, sewage sludge, and biochar are used. Biochar has great potential to improve the quality of compost. This paper reports the effects of different compost rates and feedstock types of biochar on water retention characteristics of sandy soil in a standard natural turfgrass root zone.Using soil with the texture of loamy sand, a pot experiment was established. The following mixtures of feedstocks were used in this study: compost of maize straw (MS), compost with sewage sludge (MS+SS), and compost of mixture of maize straw, sewage sludge, and biochar (MS+SS+BC). Mixtures of compost additives and soil were prepared at 0.5% (R05), 1% (R1), 2% (R2), and 4% (R4).Compared to untreated soil, the physical properties of the sandy soil were significantly improved with the application of compost. The basic physical parameters of the soil, such as bulk density and total porosity, depended mainly on the rate of the biochar additive. The differential porosity of the soil was affected by both compost rate and feedstock type. For compost with sewage sludge, the highest content of large pores with diameters above 500μm was observed, and this was achieved with biochar addition. Addition of the compost also significantly increased the volume of pores with diameters below 50μm compared to the untreated control soil. The water retention properties of the soil were improved with the compost application and were dependent on the rate of compost and the type of feedstock. The lowest value of available water content (AWC) was obtained for soil with maize straw compost. The addition of sewage sludge or biochar during the composting process resulted in an increase in AWC in the soil. The best combination of compost rates and feedstock types is maize compost with both sewage sludge and biochar at a rate of 4%.