Mechanical Composition of Hydromorphic Soils, its Significance in Soil Fertility and Accumulation of Humus Substances

Abstract

The article provides information on the accumulation of humus in various types, subtypes of hydromorphic soils common in the Tashkent oasis, depending on the mechanical composition. In the studied soils, a direct relationship was determined between the humus content and the clay fraction, as well as the physical clay of the soil. Thus, the dependence of the amount of humus of the silty fraction and physical clay is expressed by the correlation r=0.687-0.756 and r=0.527-0.734, respectively, where the relationship is medium and strong. The correlation coefficients between soil types and the content of the clay fraction are expressed in the following descending series: tugai alluvial > meadow bog> bog-meadow > meadow alluvial, with an increase towards old-irrigated meadow alluvial soils, and this situation can be explained by the fact that with the duration of irrigation and with the expiration of time, accumulation of a clay fraction in the genetic soil horizons and an increase in humic acids in its composition. Between the silt fraction of the soil and the 3rd fraction of humic acid are in irrigated bog-meadow soils r=0.750-0.820, in old-irrigated meadow-alluvial soils r=0.845- 0.925 and the relationship is considered strong. On the basis of regression and correlation statistical analysis, the changes in these indicators between types and subtypes of soils, as well as the relationship between humic acids in the fractional composition of humus with clay minerals and the 3rd fraction strongly bound by sesquioxides and the clay fraction of the soil, were proved.