HUMIC CONDITION OF BARABA SOLONETZ SOILS AFTER 27-YEAR ACTION OF SINGLE APPLICATION OF GYPSUM

Abstract

Under long-term effect of single application of gypsum (11, 23, 36, 45 and 56 tons per ha) was studied humic condition of multi-sodium solonetz soils: total carbon and humus contents, changes in group and fraction structure as influenced by soil improvers. When solonetz soils are involved in agricultural turnover, the humus content in the 0-20 cm layer has been found to reduce because of intensified microbiological processes and mineralization of humic substances. The humus content in reclaimed solonetz soils, being in long-term (20 years) fallow condition, increased up to 5 percent as compared with 3.6 percent in the control. The type of humus in the control and virgin solonetz soil is fulvate. The Cgk : Cfk ratio is approximately 0.3. In reclaimed solonetz soils, group structure of humus in the 0-20 cm layer is fulvate-humate (Cgk : Cfk > 1), and approaches the type of zonal meadow-chernozem soil. In the 20-40 cm layer, it changed to humate-fulvate. In the control, humic acids composition had fraction 2 (10 percent of total carbon in soil) prevalent. In long-term reclaimed solonetz soils, the percentage of this fraction almost doubled (18-28 percent of total carbon). As a dose of gypsum increased, the fraction 2 content bound with calcium increased as well. In the variant with the gypsum dose of 11 tons per ha, fulvic acids prevailed in the humus content, and in the variants with high doses, they considerably decreased, which was indicative of reduced mobility of humic substances.