The Effect of Digestate from Biogas Plants Alone and with the Addition of Biochar and Zeolite on Soil Properties and Sorghum Yield

Abstract

This article examines the effect of digestate from biogas plants, as well as its combinations with biochar and zeolite, on soil properties, sorghum yield, and heavy metal accumulation. The experiment was carried out in an experimental field in Czeslawice (Poland). The results showed that the incorporation of digestate increased the organic matter content, improved the availability of nutrients (nitrogen, phosphorus, potassium), and improved the soil pH. The addition of biochar was demonstrated to support the stabilization of nutrients and limit the bioavailability of heavy metals. In contrast, zeolite has been observed to enhance the mineral content of the soil, although it has also been noted that this can result in an increase in sodium and heavy metal content. The highest sorghum biomass production was obtained in soils with digestate from biogas plants and biochar, while the addition of zeolite reduced the yield. Therefore, the study confirmed that natural additives have different effects on the soil. The utilization of waste material in agriculture requires monitoring of soil quality and the judicious selection of organic waste additives. The results indicate the potential of these additives to promote sustainable agriculture and the circular economy.