Changes in organic part of the soil and acid-base balance depending on green manure fertilization in podzolized chernozem

Abstract

Aim. To study the changes in the content and stock of organic substances as well as the reaction of the soil en- vironment depending on the impact of different types of fertilization of green-manured fallows. Methods. Field studies were conducted on podzolized heavy loamy chernozem, on loess, in conditions of Right-Bank Forest- Steppe of Ukraine. Experimental design included: sweet clover with the seeding rate of 20 kg/ha, white mustard – 20, oilseed radish – 20, spring vetch – 150, and buckwheat – 150 kg/ha with the following fertilization variants: no fertilizers – control; N 40 ; P 40 K 40 ; N 40 K 40 ; N 40 P 40 ; N 40 P 40 K 40 ; N 80 P 40 K 40 . The content of total carbon and nitrogen were defi ned using Anstett’s method, modifi ed by Ponomariova and Nikolaeva; the content of total humus in the soil prior to sowing winter wheat (the impact of green manure for a year) – according to DSTU 4289:2004, pH of the water extract – according to DSTU ISO 10390:2007. Results. Nitrogen-carbon ratio was in the range from 11.1 to 11.8 in the biomass of leguminous crops and from 18.8 to 20.7 – in root remains, and its highest value was observed in root remains of Brassicaceae crops – from 28.8 to 34.5 depending on doses and types of mineral fertilizers. Compared to bare fallow, green manure fertilization promotes humus preservation in the soil. The de- crease in the level of humus intension of the soil by 0.01–0.04 % was registered both in the surface and subsurface layers in conditions of bare fallow compared to green-manured fallow. 1.67 t/ha of humus is mineralized in the soil of bare fallow. The transformation of green manure biomass allows accumulating 1.15–2.05 t/ha of humus depending on doses and types of mineral fertilizers. When the Cruciferae family (white mustard and oilseed rad- ish) are used as green manure, the isohumus index is 1.52–1.55, 1.67–1.69 – for the Leguminosae (annual sweet clover and spring vetch), and 1.52–1.60 – for buckwheat, depending on fertilization. The humifi cation coeffi cient for vegetative biomass of oilseed radish is 0.023, for spring vetch – 0.027, for buckwheat – 0.033, for white mustard – 0.035, and for annual sweet clover – 0.036. The administration of different doses and types of mineral fertilizers conditions the decrease in the coeffi cient of green manure fertilization. Conclusions. The application of green manure both with and without fertilizers compared to bare fallow promotes the preservation of humus content in the soil. The transfer of calcium from lower layers to the arable soil layer, performed by the plant root system in green-manured fallow, decreases active acidity of the soil.