Organic substances replenishment and high humus content of soil in the apple orchads under different fertilization

Abstract

The balance of humus in a meter layer of dark gray, podzolized soil and podzolized chernozem of the experimental apple orchads and the study of their long-term fertilization was investigated (from the planting to 50-year old trees) with the use of organic (40 t/ha of cattle manure) and mineral fertilizers (N120P120K120), which were applied once in two years in autumn under the plowing in the row spacings at a depth of 18 20 cm. In the 20-year period (from 30- to 50-year-old experimental gardens) in a meter layer of dark gray podzolized soil on the non-fertilized control plots the amount of humus increased by 27 t/ha, and on the plots fertilized with manure – by 7 t/ha more and on the plots with mineral fertilizers – by 6 t/ha less and in podzolized chernozem – 37 t/ha and 3 t/ha more and 10 t/ha less respectively. Such changes in humus storage were caused by different replenishment of organic substances, and, to a greater extent, an increase in the biological activity of the fertilized soil, in particular the intensity of mineralization processes of organic matter, and in particular the humus compounds. Also, the replanishment of such soils in the gardens by the organic mass of fallen leaves and thin (d≤1mm) small roots, which systematically grows and dies, providing root nutrition of fruit plants, was investigated. These sources supplemented with organic substances the layer of soil of 0 20 cm – with all the mass of leaves and 38,5 43,3% of the total roots, and the increase in humus content was in all roots of the layer of 0 60 cm: in non-fertilized areas of 11 t/ha in dark gray soil and 18 tons per hectare in chernozem, under organic fertilizers, by 14 and 19 t/ha, and under mineral fertilizers – by 3 and 9 t/ha respectively. The greatest quantity of humus was added in the layer 60 100 cm: 16 and 19 t/ha, 20 and 21 t/ha and 18 t/ha. Such results were conditioned by the intensification of biological activity, in particular mineralization processes, in the upper layers of fertilized soils at higher humus content, as well as the migration of soluble humus substances deep into the meter profile.