WATER-SOLUBLE HUMUS CARBON DYNAMICS IN COMMON CHERNOZEM OF KRASNOYARSK FOREST STEPPE IN THE PURE AND BINARY MELILOT CROPS

Abstract

The humus state of common chernozem in the pure and binary melilot crops was studied. The field experiment was carried out in 2013–2015 in the Krasnoyarsk forest steppe area. The effects of the pure and binary melilot crops on the humus state of soil were studied in the following crop rotations: barley – fallow + winter rye – winter rye; barley + melilot – melilot + winter rye – winter rye; melilot – melilot + winter rye – winter rye. The agroecosystems of crop-fallow and crop-grass rotation links functioning on the soil with high humus content determine varied replenishment of humus reserves. The binary crops of melilot and barley determine the increase in total carbon reserves by 4 per cent (111 t/ha) as compared with the pure melilot crops. The multidirectional character of water-soluble humus carbon dynamics is determined by the structure of a crop rotation, the amount of plant residues and hydrothermal conditions. Increased moisture reserves in common chernozem contribute to the enhancement of humus mineralization and decrease in its amount in soil. The seasonal dynamics of water-soluble humus in the arable layer of chernozem under the pure and binary melilot crops by 52–46 per cent is connected with the soil moisture dynamics. The melilot lifetime termination determines a relative increase in the water-soluble humus carbon content by 17–31 per cent. The pure melilot crops of the second year of lifetime form a pool of C_H2O reaching 0.51–0.59 tonnes of carbon per ha in the 0–40 cm layer of chernozem.