The digestate is a prospective biofertilizer and potential source of income for many biogas plants worldwide. However, its actual impact on the soil properties and biomass yield is still unexploited. The different digestates from eight agricultural biogas plants were researched in terms of their chemical composition and the fertilizing potential. The results obtained from digestate chemical analysis indicate that the digestate biomass had large amount of nitrogen (up to 73 g kg⁻¹ fresh mass) and potassium (up to 25 g kg⁻¹ fresh mass). The value of the digestate was estimated in the range of 2.88–7.89 EUR Mg⁻¹ for liquid digestate and 7.62–13.61 EUR Mg⁻¹ for solid digestate based on the commercial fertilizer market price of nitrogen, potassium phosphorus, organic carbon, Cu, Zn, Fe and Mg. The digestate produced at the 1 MW biogas plant is worth EUR 941–2095 per day in addition to energy sales income. The application of digestate on low-fertility land in areas close to the biogas plant allows the production of up to three-fold more biomass suitable for biogas production. The digestate’s application on semi-natural grass biomass production in the low-fertility soils near the biogas plants could be an alternative strategy for the biogas plant feedstock portfolio diversification.

Climate change, new varieties, better technological abilities, and increased demand for local resources provide significant reasons to introduce soybeans in northern regions, above the typical soybean distribution area in Europe. This research examined the effects of two delayed sowing times, wide 25 cm and 50 cm row spacings, seed inoculation with Bradyrhizobium japonicum, and the interaction of all these factors on soybean development and productivity in an organic farming system. Length of soybean vegetation varied from 142 to 161 days at latitude 55° N. Yield varied from 673 to 3154 kg ha⁻¹ in response to management factors. In the dry 2015 year, the combination of later sowing dates and wide 50-cm row spacing significantly (p < 0.01) increased the number of pods per plant by 28%, aboveground dry biomass by two times, and seed yield by 36% plant⁻¹. In the wet 2016, yield components reached their highest values of 16.8 g dry biomass, 19.9 pods plant⁻¹ and 7.9 g seeds plant⁻¹ when inoculated soybeans were sown earlier, with 50-cm row spacings. Protein content significantly varied from 27.4 to 35.3%, and fat content 17.4–21.5%. This study suggests that regular soybean development could be maintained in organically managed locations above the present northern soybean distributional region, but its development, productivity, and production quality significantly depends on management practices.

Microbial-based biostimulants that increase plant performance and ensure sustainable restoration of degraded soils are of great importance. The aim of the present study was to evaluate the growth promotion ability of indigenous Trichoderma ghanense, T. tomentosum and their complex on early rye seedlings in sustained grassland and arable soil. The impact of soil chemical properties on the ability of selected Trichoderma strains and their complex to promote plant growth was determined by the evaluation of the rye (Secale cereale L.) early seedling growth—measuring the length of shoots and roots as well as their dry weight. Trichoderma species were tested for their ability to produce extracellular degradative enzymes on solid media. Furthermore, the soil properties and CM-cellulase activity of soil were estimated. The indigenous Trichoderma strains possess the capacity to produce enzymes such as peroxidase, laccase, tyrosinase, and endoglucanase. The results indicated a significant (p < 0.05) increase in plant growth and the improvement of some soil chemical properties (total N, mobile humic and fulvic acids, exchangeable K₂O, soil CM-cellulase activity) in inoculated soils when compared to the control. The growth of the roots of rye seedlings in sustained grassland was enhanced when T. tomentosum was applied (p = 0.005). There was an increase in total weight and shoot weight of rye seedlings when T. ghanense was used in the arable soil (p = 0.014 and p = 0.024). The expected beneficial effect of Trichoderma spp. complex on rye growth promotion was not observed in any tested soil. The results could find application in the development of new and efficient biostimulants, since not only do physiological characteristics of fungi play an important role but also the quality of the soil has an impact.