3rd TAGRA

Biomass ash (BA) represents a promising secondary resource for the restoration of degraded soils, provided that its application rate is optimized and its nutrient limitations are addressed. This study evaluated the potential of BA to improve soil properties and plant performance by first conducting controlled pot experiments and subsequently validating selected treatments under field conditions. In the pot experiments, BA was applied as a sole amendment at rates of 1, 2.5, 5, and 7.5% (w/w) to assess its effects on soil chemical and biological properties and plant growth. Biomass ash increased soil pH, electrical conductivity, and the availability of P, K, Ca, and Zn. Low application rates (1% and 2.5%) improved soil properties and enhanced plant biomass, whereas higher rates adversely affected both soil conditions and plant growth. Nitrogen deficiency was identified as a major limitation of BA applied alone. Based on these findings, a field experiment was established on a brownfield soil using lower BA rates (1% and 2.5%), applied alone or in combination with digestate, with Miscanthus × giganteus (M×g) as the test crop. During the first year of the field experiment, some of soil parameters, particularly pH, did not differ significantly among treatments, which is consistent with the limited short-term response often observed under field conditions. However, nutrient concentrations, especially K and P, increased in the amended treatments. At the brown harvest, the BA 2.5%, Digestate, BA 1% + Digestate, and BA 2.5% + Digestate treatments all produced significantly higher biomass than BA 1%, with the highest mean recorded for BA 2.5% + Digestate. These results suggest that low-dose BA, particularly when combined with other organic amednments, has potential for improving soil nutrient status and supporting M×g performance; however, longer-term field monitoring is needed to determine the persistence and practical significance of these effects under field conditions.