Natural features and rational use of water resources in rice irrigation systems of Kazakhstan

Abstract

Akdala rice irrigation system is located on a high above-floodplain terrace of the Ili river basin, the geological structure of the top layer of soil is represented by 50 varieties that affect the rate of water consumption and rice yield. The soils are alluvial-meadow and takyr, the lithological composition of the aeration zone soils is characterized by a wide variety, differing in mechanical composition, water-physical properties and the degree of salinity. Water filtration on sandy loam, light loam, loam with layers of sandy loam rice paddies during rice irrigation constitutes 12-17 mm/day, which provides water renewal in rice paddies and removal of salts from the root layer of the soil. Rice is grown without flow and discharge of water from rice paddies, the rice yield is 6,8 t/ha and higher. Water filtration on heavy loam, loam with layers of clay soils rice paddies during rice irrigation constitutes 5-3 mm/day. On these soils, due to the convective diffusion of salts from the soil and from ground water, the salinity of water on rice paddies increases and reaches the critical threshold of toxicity of 2,5 g/l. To reduce the salinity of water in the paddies, water is discharged, with subsequent flooding from the irrigation channel, the rice yield is 4,8 t/ha. The rice paddies water balance of the incoming and outgoing is stable. In the aeration zone during the irrigation period desalination occurs in salt balance; in autumn-winter period salts from the lower horizons are redistributed to the upper ones. Rice cultivation, taking into account the geological structure and lithological composition of soils in the aeration zone, provides a profit per hectare of 86,988 tg/ha, the profitability ratio is 25,5%.