The potential of digestate as a biofertilizer in eroded soils of Lithuania

The objective of this work was to determine the potential of using of solid and liquid digestate, as biofertilizer and soil amendment, and to address adverse unfertile soil erosion problems after analysing areas of potential use. We found a high concentration of organic carbon in a solid fraction of the digestate, which indicates a significant potential for returning carbon to the soil. The influence of digestate fertilization on soil fertility as a function of the amount of available phosphorus (P₂O₅) and potassium (K₂O) in the 0-40 cm layer was found to be very important. The soil fertility category was changed from "high" (200-300 mg kg^-1) to "very high" (>300 mg kg^-1) according P₂O₅, using only 170 kg ha^-1 of nitrogen in solid and liquid digestate rate. Fertilization with all phases and rates of digestate tend to increase the amount of K₂O. The solid digestate fertilization using the 170 kg ha^-1 N rate showed a significant increase (5 times) of mineral nitrogen content in the 0-40 cm soil layer. The advantage of solid digestate as a soil improver has been highlighted because it has a positive effect on soil fertility, quality, sustainability and durability. The amount of mobile humic acids (MHA) in eroded loamy Retisol increased 1.6 times in soil 0-40 cm layer with a fertilization rate of 170 kg ha^-1 and 1.5 times - of 85 kg ha^-1 of solid digestate compared to the untreated. Similar trends of MHA but in lower amount were identified when liquid digestate was applied.