Abstract
Aim. To investigate the focus of the mineralization–synthesis processes in leached chernozem while cultivating potatoes in different fertilization systems, ensuring different supplies of raw organic matter into the soil. Methods. Field experiment, gas chromatography. Results. The study of emissions of nitrous oxide and carbon dioxide from the soil followed by the calculations of the specifi c losses of N-N2O (g/kg C-CO2), depending on fertilization system and in comparison with the indicators of the “reference” soil, provide an opportunity for rapid determination of the focus of the mineralization-synthesis processes in the organic matter in agrocenoses. The use of exclusively mineral fertilization systems results in the highest specifi c losses of N2O as the increase of the applied fertilizer doses initiates the mineralization processes in the soil. The combination of mineral fertilizers with raw organic products (5 t/ha straw and 13 t/ha of lupine cover crop) signifi cantly improves the situation. At the same time, in experiment with the lowest (N40P40K40 kg/ha) and medium (N80Р80К80 kg/ha) doses of mineral fertilizers the balance of mineralization-synthesis processes of organic matter was observed. The highest rate of mineral fertilizer dose in the experiment (N120P120K120 kg/ha), even in combination with the raw organic material, activates mineralization processes. With the use of manure, as well as upon its combination with the lupine cover crop and low doses of mineral fertilizers, the optimization of nitrous oxide and carbon dioxide emissions is observed. Conclusions. The use of solely mineral fertilizers in the technology of potato cultivation is inappropriate in terms of environmental reasons. The combination of mineral fertilizers (not exceeding N80Р80К80 kg/ha dose) with straw and lupine cover crop ensures optimization of the processes of mineralization-synthesis of organic matter. Moreover, the optimization of biological processes in the soil was observed in experiments with the use of manure, its combination with lupine cover crop and low doses of mineral fertilizers. The calculations of the indices of mineralization-synthesis of organic matter, considering the emission factors of N2O and CO2, obtained with the use of modern high-sensitivity gas chromatographic methods, allow to determine the focus of biological processes in the soil, depending on fertilization system, and to estimate ecologic sustainability of types and doses of fertilizers.
Highlights
The determination of gas emission from soil under potatoes during the emergence phase demonstrated the highest losses of N2O in variants with the introduction of manure into soil, its combination with green manure mass, organo-mineral fertilization, and the highest dose of mineral fertilizers in the experiment (Table 1)
As there is no sufficient amount of fresh organic matter in soil, it may indicate the mineralization of conservative organic substances
The discussion point about the conclusions of some researchers (Doran J.W. et al, 1996; Margdoff F. et al, 1997; Purtova L.N. et al, 2016) regarding the destructive impact of mineral fertilization systems for agricultural crops on the humus state of soils is confirmed with the data of gas chromatography determination of the emission of N2O and CO and subsequent calculations of the specific losses of N-N2O and indices of mineralization–-synthesis of organic matter
Summary
Taking the abovementioned into consideration, the aim of our present research was to study the focus of mineralization-synthesis processes in leached chernozem while cultivating potatoes using the abovementioned methodological approaches (Volkogon et al, 2019)
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