PROPERTIES OF MEADOW-CHERNOZEM SOILS AFTER CROP ROTATION WITH VARIOUS WATER LOADS AT CYCLIC IRRIGATION OF RICE FIELDS

Abstract

Purpose: to study the effect of crop rotations with different water loads during cyclic irrigation on soil fertility in rice irrigation systems. Materials and methods. The object of the research is the meadow-chernozem soils of Bagaevsky district Rostov region, which are developed in five crop rotations with different rice saturations from 60 to 25 % and, therefore, different water loads. A fallow that has not been developed for more than 10 years has been taken as control. Analysis and evaluation of the results of the study of soil and water samples were carried out according to generally accepted methods. Results and discussion. The studied properties of meadow chernozem soils after rice crop rotations with different water loads indicate an increase in the negative processes in variants with rice saturation of more than 50 %. So, in the variant with an annual irrigation rate of 14000 cubic meters per hectare, due to 65 % rice saturation in a six-field crop rotation, the water tables were located at a depth of 135 cm, the total salt content in the layer 0–40 cm compared to the control (fallow) increased by 63 %, and in the meter deep layer by 91 %. In the soil absorption complex (SAC) of this soil, the amount of exchangeable sodium reached 14 % with a decrease in calcium content to 55 % of the amount of SAC. In the control these indicators amounted to 4 and 71 % of the SAC sum, respectively. The soil has become very compacted, has lost water resistance and microostructure of aggregates. The decrease in the total humus content compared to the control was 43 %. Conclusions. To preserve soil fertility in rice irrigation systems, crop rotations with rice saturation less than 50 % should be introduced, and the frequency of irrigation during cyclic irrigation should be two to three years.

Keywords

• soil properties
• crop rotation
• cyclic irrigation
• rice irrigation systems
• fertility