HUMUS BALANCE MANAGEMENT IN SHORT-ROTATION CROP SYSTEMS OF SMALL FARMING ENTERPRISES IN THE WESTERN FOREST-STEPPE OF UKRAINE

Abstract

The article investigates humus balance dynamics in a three-field shortrotation crop sequence (soybean – winter wheat – potato) practiced on small private farms in the Western Forest-Steppe of Ukraine. The study was conducted on dark-grey podzolized soils with an initial humus content of 3.6% (approximately 140 t/ha in the 0–30 cm arable layer at a bulk density of 1.3 g/cm³). Humus balance was calculated using the methodology of Baliuk et al. (2011), applying humification coefficients of 0.16 for legume post-harvest residues, 0.20 for cereal straw, and 0.06 for semi-liquid manure. Mineralization intensity was assessed at 1.2% of total humus stock per year under conventional plowing and 1.0% under minimum tillage. Climate warming of approximately 1.74° C in the Forest-Steppe zone has notably extended the growing season and created practical agronomic conditions for soybean cultivation in areas where it was previously considered marginally suitable, making short soybean–wheat rotations increasingly common among private farms in the region. The results demonstrate that under conventional tillage, the annual humus balance is negative (–0.33 t/ha per year), even with full straw incorporation, incorporation of root and post-harvest residues, and modest manure application. The transition to minimum tillage reduces the deficit to –0.24 t/ha per year but does not independently achieve humus equilibrium. The introduction of a high-biomass legume-cereal green manure mixture as an intercrop, combined with minimum tillage, provides approximately 1.0 t/ha of additional humus input and generates a positive overall balance of +0.09 t/ha per year, confirming the feasibility of gradual soil organic matter restoration within a short rotation. It is recommended that small farming enterprises in the Western Forest-Steppe adopt minimum tillage combined with systematic use of legume-cereal green manure mixtures as the core strategy for humus balance management in shortrotation cropping systems.