Possibilities of Soil Management in Improving Soil Fertility, Biological Activity, and Soil Health

Increasing organic matter content enhances soil structure, water-holding capacity, nutrient mineralization, biological activity, and the infiltration of water and air. However, the long-term functional roles of organic inputs after entering the soil remain poorly understood. These processes were investigated within a long-term litter manipulation experiment (DIRT) established 25 years ago in the Síkfőkút deciduous forest, Hungary. The main objective of the project is to assess how long-term quantitative and qualitative changes in plant litter inputs influence soil organic matter accumulation and transformation. The applied treatments were Control, No Litter, No Input, No Roots, Double Litter, and Double Wood. Our aim was to compare the long-term effects of sustained organic matter removal or doubling on soil biological activity, permanganate-oxidizable carbon (POX-C), and mycorrhizal colonization. The decrease in POX-C between the 0–5 cm and 5–15 cm soil layers was greatest in the four treatments receiving surface litter, with an average reduction of 28%, while litter-free treatments showed a much smaller average decrease of 11%. This highlights the importance of surface litter in maintaining labile soil carbon. Similar long-term trends were observed in soil biological activity. In the 0–5 cm layer, easily extractable glomalin (EE-GRSP) differed significantly between the Control and organic matter removal treatments without surface litter, and between the Double Wood treatment and all others. In the 5–15 cm layer, the Double Wood treatment differed from the removal treatments. Overall, long-term litter removal had a significantly stronger impact on soil biological activity than increased organic matter inputs.