No abstract

No abstract

This paper describes soil chronosequence studies relating to fertility evolution of meadow-chernozemic (Gleyic Chernozem) soil of the Kuban region. The research has been conducted in the rice irrigation system of Krasnoarmeysky district, Krasnodar Krai. Over the course of 80 years with 12-year intervals, soil was sampled from pits from the plots/checks with permanent rice cultivation, or with crop rotation as well as from fallow land. Changes of morphological, physical and physico-chemical soil characteristics were studied. Rice paddy cultivation results in removal from the plow layer organic substances, carbonates, mineral elements, and silt particles, i.e. of the components responsible for stable soil development in the irrigation system. This illustrates the expression of dehumification, lessivage, and degradation soil processes with rice cultivation permanently as a monoculture or in a crop rotation during the chronosequence study. Deterioration of the soil physical condition is one of ever-increasing factors.

The study investigates an anthropogenous influence on the humus content in meadow and meadow-bog soils under rice cultivation in Adygea (Gleyic Phaeozems and Calcic Chernic Gleysol). A field experiment focused on the use of mineral fertilizers N0P0K0 (control); N90P60K45; N120P80K60; N150P100K75 and N180P120K90 is carried out on rice paddies. Soil samples are taken from the plow layer before seeding and after harvesting of rice; a total humus content and fraction-group composition are studied. An increase in fulvic acids is detected in soils as a consequence of dominant reduction and oxidative degradation of humic acids. Heightened amounts of fertilizers make humus more fulvic. A labile fraction in the total humus content is determined to be 7.97-11.02 % in meadow soil and 5.38-8.33 % in meadow-bog soil. In labile humus of meadow soils fulvic acids prevail over humic acids (HA-1: FA (1a+1) = 0.71-0.89). A share of fulvuc compounds is higher in meadow-bog soils (HA-1: FA (1a+1) = 0.38-0.55). Mineral fertilizers taken in ratios of N150P100K75 and N180P120K90 raise a percentage of newly formed humus substances.