Nitrogen-carbon circulation in agrocenoses with different fertilization systems

Aim. To compare nitrogen-carbon circulation in organic and intense fertilization system in agrocenosis of a short crop rotation with grain and intertilled crops on podzolic highly-regraded low-humus chernozem in the Central Forest-Steppe of Ukraine. Methods. Summarization of the study results in the permanent fi eld experiment, statistical method, dispersion method, correlation analysis of performance parameters, structures of phytomass, quality and quantity items of carbon and nitrogen balance. Results. In the organic system of fertilization, the removal of N increased to 0.25 units per capacity unit of nitrogen balance, which is 1.47 times higher, and the total loss of N increased 1.1 times (0.31 units per capacity unit of nitrogen balance) regarding the intense system of fertilization, but with lower values of balance items for nitrogen in the agrocenosis. Direct and strong correlation relationships were revealed between the yield of fodder units and the content of organic carbon in the structural components of the total phytomass: with organic carbon in the main products and root mass – R = 0.86–0.88 ± 0.02; R^2 = 0.74–0.77, and with the content of organic carbon in by-products and non- commodity total phytomass the relation to the yield of fodder units was on the level of direct mean correlation: R = 0.58–0.65 ± 0.02; R^2 = 0.34–0.43. The increase in the yield of fodder units is accompanied with the 1.32- fold decrease in the nitrogen balance capacity regarding the intense system of fertilization. Conclusions. It was established that in case of organic system of fertilization the ratio of organic carbon and N in the agrocenosis of a short crop rotation is the most optimal and approximates 30:1, which is the most profi table for humifi cation of by-products and decrease in the intensity of humus mineralization. Balance capacity is a restrictive factor in the circulation of organic carbon and N at the organic fertilization system, as it may considerably concede the balance capacity of organic carbon and N at the intense fertilization system, which had a negative impact on the performance of crop rotation.