Carbon turnover and state of humus in typical chornozem for long-term use of fertilizers in 4-field crop rotations

Abstract

Goal. To determine the volumes of carbon intake and the content of humus in the typical weakly saline chornozem at long-term use of organic and mineral fertilizers in 4-field crop rotations. Methods. Field (determination of the influence of fertilizer systems and crop rotation structure on the content of humus in the typical chornozem), analytical (determination of the content of humus in the soil using the Tiurin method), and analysis of variance using the Statistica-2010 computer program. Results. The study was conducted in a stationary field experiment at the Veselopodilskyi Experimental Breeding Station (VPEBS) of the Institute of Bioenergy Crops and Sugar Beets of the NAAS in 2022 – 2024. The influence of organic and mineral fertilizers in 4-field crop rotations on the content of humus in typical chornozem was established. It was found that organic and mineral fertilizer systems formed a higher content of humus in the fruit rotation than in the row-crop and grain rotation. It was found that fertilizer systems enriched with organic matter increased the accumulation of humus in the soil of all crop rotations. Conclusions. The use of by-products as fertilizer in 4-field grain-beet crop rotations contributed to a significant replenishment of the soil with organic matter. For the introduction of by-products + N46,4P33,6K33,6 per 1 ha of crop rotation, the volumes of carbon intake into the soil in the fruit-changing crop rotation amounted to 1.81 tons/ha, the grain-row-crop production — 1.82, the row-crop production — 1.81 tons/ha of crop rotation area, which was 1.5–1.8 times more than for the introduction of 6.3 tons/ha of manure + N33,6P33,6K33,6 per 1 ha of crop rotation. The long-term use of by-products + N46,4P33,6K33,6 ensured the preservation and reproduction of humus in the soil at a level with traditional organo-mineral fertilization. With alternative fertilization, the content of humus in the soil of fruit-changing crop rotation was 4.72%, grain-row-crop — 4.46, row-crop — 4.53%, with traditional based on cattle manure — 4.70%, 4.46, and 4.51%. In fruit rotation for 46 years of use of 6.3 tons/ha of manure + by-products + N33,6P33,6K33,6 per 1 ha of crop rotation, the most favorable conditions were created for the preservation and reproduction of humus in typical weakly salted chornozem. Its content was 4.78%, which exceeded the control without fertilization by 0.97%.