OPTIMIZATION OF NITROGEN FERTILIZATION FOR AGRICULTURAL CROPS UPON ADDITIONAL APPLICATION OF FRESH ORGANIC MATTER TO THE SOIL

Abstract

Objective. Using biological testing, determine the environmental appropriate rates of mineralnitrogen, applied in the background of effect and aftereffect of straw and biomass of intermediatelupine green manure, in the fertilization system of potatoes and spring barley. Methods. Field experiment (growing crops in crop rotation in the conditions of a long-term (since 2009) stationaryexperiment on leached chornozem); gas chromatographic (to determine the potential nitrogenfixing (nitrogenase) and potential denitrifying activities in the rhizosphere soil of plants dependingon the fertilizer); statistical. Results. With the systematic application of fresh organic matter to thesoil in the form of 5.0 t/ha of straw and 5.3 t/ha of dry biomass of intermediate lupine green manure, the excess of nitrogen mineral compounds is metabolically bound (immobilized) by microorganisms, the process of nitrogen fixation is restored, the emission of N2O decreases, and the ratesof mineral fertilizers not exceeding N80P80K80 become environmentally appropriate when growingpotatoes. At the same time, the introduction of straw does not require additional provision of mineral nitrogen to optimize the C/N ratio. The highest rate of mineral fertilizers N120P120K120 in theexperiment, even when combined with organic matter for a long time is environmentally inappropriate — only at the end of the growing season, the studied indicators demonstrate its acceptability.When growing spring barley on leached chornozem, the optimization of the processes of biologicaltransformation of nitrogen compounds is achieved if mineral fertilizers are applied on the background of aftereffect of organic matter in a rate not exceeding N60P60K60. Systemic application ofN90P90K90 suppresses the activity of nitrogen fixation and ensures significant losses of nitrous oxide.This rate of fertilizers should be applied only on the condition that it is applied against the background of the aftereffect of straw and green manure mass, which contributes to the mitigation ofenvironmental consequences. Conclusion. The use of mineral fertilizers against the backgroundof systematic application of winter wheat straw and intermediate lupine green manure biomass tothe soil contributes to the optimization of the biological state of the leached chornozem. The improvement of environmental indicators contributes to the growth of the yield of agricultural crops.