Influence of Long-Term Application of Fertilizer Systems on Fertility of Ordinary Carbonate Chernozem in the Conditions of the Central Ciscaucasia
The paper studies the influence of systematic application recommended and estimated mineral (N69P63K45 and N141P68K60) and organomineral (manure 8 t/ha + N44P42K24and manure 15 t/ha + N87P36K7) fertilizer systems within grain-grass-hoe crop rotation on density, porosity, structural condition of soil, water stability of structural units, water permeability, change of humus content and basic nutrition elements in rainfed conditions and at irrigation in comparison with their initial content and with indicators in control option – without fertilizers and irrigation throughout long-term field experiment on ordinary carbonate chernozem in a steppe zone of the Central Ciscaucasia. It is defined that over 68 years of experiments the content of total nitrogen, phosphorus, potassium and reaction of soil solution did not change. The maximum losses of humus and available forms of nutritious elements occurred in options without fertilizers in rainfed and irrigated conditions, bulk density of soil increased, porosity and water permeability decreased. The use of fertilizers improved agrophysical and water properties of soil: its density decreased, porosity, structure index, water stability, water permeability and hygroscopicity increased. The introduction of estimated organomineral fertilizer system to the scheme of experiment since 1986 restored the humus content in soil to the reference value and ensured its positive balance (+2.6 t/ha).
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