Effect of tillage methods on directionality and intensity of microbiological processes in gray forest soil

I. M. Malynovska; S. A. Gavrilov

doi:10.15421/041405

I. M. Malynovska NRC “Institute of Agriculture of the NAAS”
S. A. Gavrilov NRC “Institute of Agriculture of the NAAS”

Keywords: soil tillage, ammonificators, Azotobacter, polysaccharide-synthesizing microorganisms, melanin-synthesizing microorganisms, organic matter development, humus mineralization, phytotoxicity

Abstract

The direction and intensity of microbiological processes in the gray forest soil with different ways of its primary tillage has been investigated. It has been established that the method and depth of primary tillage affects the abundance and physiological and biochemical activity of microorganisms of most studied ecological, trophic and functional groups. Soil after plowing characterized with the lowest number of microorganisms, and soil after surface cultivation – with the largest. The total number of microorganisms in the control variant with surface cultivation exceeds the number of bacteria in the control variant with plowing at 2,10 times, with bringing of by-products – at 2,03, with fertilization – at 1,31 times. Method of soil tillage affects the number of Azotobacter: fertilization with plowing and disking leads to a significant increase the number of microorganisms and the change of the dominant species of Azotobacter vinelandii on A. chrooccocum. Fertilization with using of surface cultivation leads to decrease the number of Azotobacter population at 3,3 times, while change in the dominant species does not occur. Adding by-products leads to an increase the number of Azotobacter, because the C/N ratio in the soil is increasing. Adding crop by-products which contain large amounts of polysaccharide molecules with the ability to accumulate a variety of pollutants promotes a decrease pressures on agroecosystem, resulting in a decrease the proportion melanin-synthesizing micromicetes in the total number of microscopic fungi. Adding crop by-products together with mineral fertilizer by-products which are composed of undesirable impurities again leads to an increase the proportion of melanin-synthesizing micromicetes. Tillage affects the activity of organic matter development: this process is more active with the use of plowing than process with the use of disking and surface cultivation. Adding by-products can significantly reduce the activity of organic matter expenditure: with plowing – by 146,6 %, with disking – 16,9, with surface cultivation – by 28,8 %. The combined use of by-products with chemical fertilizers can reduce this figure even greater extent due to better plant growth in these experimental variants and the allocation of root exudates that affect the course mineralization processes in soil. Tillage variants differ in their effects on mineralization activity of humic substances. Ploughing leads to the activation of this process: humus mineralization activity in the control variant is higher than in variants with disking and surface cultivation by 11,9 and 49,6 %, respectively. Maximum deceleration of humus mineralization is achieved with soil surface tillage. The toxicity of the soil is the smallest with the use of plowing, especially in the form of plant mineral nutrition optimization and adding of by-product precursor. A possible reason for this may be the oxidation of toxic substances with oxygen that has more access in comparison with the soil surface disking and cultivation.

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