Long-term effects of fertilisation systems on soil nutrient status, soil organic carbon content and crop productivity in a typical Chernozem under different crop rotations

The aim of this study was to evaluate the long-term effects of fertilisation systems and crop rotation structure on soil nutrient status, organic carbon (OC) content and stocks, and crop productivity in a typical Chernozem. The study was conducted during 2019-2024 as part of a long-term field experiment established in 1976 at the Bila Tserkva Experimental Breeding Station in the Right-Bank Forest-Steppe of Ukraine. Four fertilisation treatments were compared in cereal-fodder-row (CFR) and cereal-row-crop (CRC) rotations: unfertilised since 1976, mineral fertilisation with straw incorporation, mineral + cattle manure fertilisation, and organic fertilisation. Soil mineral N, plant-available P, exchangeable K, OC content, and OC stocks were determined in the 0-30 cm soil layer. Crop yields were assessed for winter wheat, sugar beet and spring barley. The mineral + cattle manure treatment generally maintained favourable soil nutrient conditions and resulted in the highest OC content and stocks in both crop rotations, reaching 1.98% and 70.8 t C/ha in the CFR rotation and 1.77% and 63.2 t C/ha in the CRC rotation. However, the higher nutrient inputs under this treatment did not result in proportionally higher residual availability of all nutrients. Under sugar beet, its clearest post-harvest advantage was observed for soil mineral N, whereas exchangeable K was not consistently higher than under the other fertilised treatments, and plant-available P in the CFR rotation did not differ significantly between the mineral + straw and mineral + cattle manure treatments. The highest mean yields of winter wheat, sugar beet and spring barley were generally obtained under the mineral + cattle manure treatment. Sugar beet root yield reached 46.9 t/ha in the CFR crop rotation and 42.2 t/ha in the CRC rotation, compared with 18.8 and 17.1 t/ha, respectively, in the unfertilised treatments. The results demonstrate that combining organic and mineral nutrient sources with crop residue return and an appropriate crop rotation structure is an effective strategy for maintaining typical Chernozem fertility and sustaining crop productivity under unstable moisture conditions.