The influence of organic–mineral fertilization system and the structure of crop rotation on the humus condition of leached chernozem

Abstract

Purpose. To study the influence of organic-mineral fertilization systems and the structure of crop rotation on the transformation of organic matter and the state of humus in leached chernozem.
 Меthods. Long-term field and analytical.
 Results. Research data on the amount of organic matter entering the soil, its humification, and the effect on the humus content in leached chernozem, depending on fertilization systems and the structure of crop rotation, are given. It was established that under the mineral fertilization system, the humus content in the soil was the lowest and demonstrated a negative seasonal dynamic. The stability of the humus content in the soil was ensured by traditional and alternative organic-mineral fertilization systems.
 Conclusions. The content of humus in leached chernozem mainly depended on the fertilization system and slightly depended on the crop rotation structure. Application of N90Ρ90Κ90 + straw + green manure or N48.8Ρ45Κ55 + by-products + green manure per 1 ha of crop rotation under sugar beet during 20 years provided the highest humus content in the soil. The content of humus was 4.04–4.07% in the 0–30 cm soil layer and 3.79–3.81% in the 30–50 cm layer, which was higher compared to mineral fertilizations by 0.18–0.20% and 0.06–0.08%, respectively. The alternative organic-mineral fertilization system stabilized the humus content in the soil at the level of the conventional manure-based fertilization system. In the mineral fertilization system, the humus content in the soil of the crop rotations decreased at the end of the vegetation season compared to the initial indicator by 0.02–0.03%, while in the organic-mineral fertilization system it increased by 0.02–0.04%. The humus content remained stable in the 30–50 cm soil layer. The alternative fertilization system with the application of mineral fertilizers, straw and green manure had the highest stabilization effect on the state of soil humus. The application of N90Ρ90Κ90 + straw + green manure provided the highest amounts of organic matter entering the soil in crop rotations − 3.55–3.57 t/ha accompanied by high humification coefficients: 22 % in a crop rotation with two fields of soybean, 41 % with barley and pea mix as preceding crops, and 44 % with pea, vetch and oat mix as preceding crops. The influence of the structure of crop rotation on the state of humus in leached chernozem was found insignificant.