EVALUATION OF AGRO-AMELIORATIVE CONDITION OF THE MAIN TYPES OF SOILS OF RICE CROP ROTATION
Authors: Ushkarenko V. O. , Dudchenko K. V. 
Published: November 2019

Relevance of research. The most common irrigation regime for rise in the world is constant flooding.

Soils of rice crop rotation undergo significant changes during the construction of rice irrigation systems, and during their operation. This leads to the formation of so-called "rice soils" that is the result of the transformation of full-profile soils, which were partially or completely disturbed when planning and building rice checks. Keeping the water layer in the field for 4-5 months leads to irreversible changes in the morphological, physical and chemical soil properties. Therefore, it is relevant to determine the indicators of the soil cover, taking into account the features of the soils of rice crop rotations, in order to prevent the development of degradation processes and increase the productivity of rice crop rotation.

The purpose of the study is to determine the main indicators of soil cover of rice crop rotation and their testing on a rice irrigation system with an area of ​​190 hectares.

Methods and methods of research. During the study the following methods were used: field method - to study the basic soil properties; laboratory one - to study of physical and chemical, ameliorative, agrochemical soil properties and chemical composition of irrigation, subsoil, drainage and waste water; mathematical and statistical, comparative and retrospective - to evaluate the study results of the basic soil fertility indices.

The research was carried out in the area of a rice irrigation system with 8-field crop rotation, where the proportion of rice does not exceed 50%. Rice was grown in accordance with the technology of rice growing, taking into account environmental protection requirements. For the companion crops, commonly used cultivation technologies were used. The system has been operated in a project mode for 50 years. The soil cover of the investigated system is represented by dark chestnut alkalized (72.9 hectares), meadow solonetz(18.9 hectares) and meadow chestnut alkalized (75.8 hectare) soil types.

Research results. On the basis of analysis of retrospective data of monitoring study of  the main indicators of agro-amelioration status of soils under rice crop rotation, the indicators of soil condition for the main soil types of rice irrigation systems were determined: groundwater level, groundwater mineralization, content of light-soluble salts in arable layer, chlorine ions content in soil-water extract, toxic salt content, soil salt balance, humus content, the content of easily hydrolyzed nitrogen compounds, the density of upper humus layer, the content of air-dry aggregates, content of water-stable aggregates.

Conclusions. The approbation of the developed soil condition indicators on the rice irrigation system of the Rice Institute of the National Academy of Agrarian Sciences was carried out, which enabled to identify the main problems and specify the ways to overcome them. In the areas with meadow chestnut alkalized and meadow solonetzsoil types, it is necessary to increase their drainage capacity, namely to repair drainage networks. In the whole area of the investigated rice irrigation system, it is necessary to increase the proportion of perennial legumes and fallow land in the crop rotation, to do soil slitting or other types of mechanical soil treatments to improve its structural and aggregate composition, in particular, the content of air-dry soil aggregates in size of 0.25-10,00 mm and water-stable soil aggregates larger than 25 mm.