Water needs of interplanted crops on rice irrigation systems

Abstract

Relevance of research. Recent studies of weather and climatic conditions of the rice-growing zone of Ukraine indicate a steady tendency to increase the aridity of the climate in the region. Further increase in air temperature and decrease in natural water availability of these territories will lead to the increase in total evaporation and water needs for irrigation of the crops of rice crop rotation. Under such conditions a significant exacerbation of the existing problem of water deficit is expected in the region. The availability of water resources directly affects the efficiency of agricultural production on the irrigated lands of rice systems. In this regard, there is an objective need to adapt agricultural production on the irrigated lands of rice systems to the existed and predicted climate change, which, first of all, requires the assessment of water needs for irrigation both the leading crop of flooded rice and the interplanted crops of rice crop rotation.
 Aim of the study is to estimate the changes in water needs for irrigation of the interplanted crops of rice crop rotation in the variable natural-agro-reclamation conditions of rice system functioning. To achieve this goal, the authors implemented a large-scale computer experiment, based on a complex of predictive-simulation models, which basing on a long-term forecast, allow to estimate weather and climatic conditions, water regime, water regulation technologies and the productivity of reclaimed lands. During the experiment the conditions of total evaporation formation were investigated, the water needs of different types of interplanted crops of rice crop rotation were determined for the technology and regime of water regulation on the irrigated lands of rice systems for the typical groups of vegetation periods of target years in view of general heat and moisture provision. It was evaluated technological efficiency of irrigation of the interplanted crops of rice crop rotation in the variable natural-agro-reclamation conditions of rice system functioning and obtained results with the actual production data were compared. 
 Research methods. The research methods were based on the application of system theory along with the systematic approach, system analysis and modeling oriented on widespread use of computers and related software in the developing of modern approaches to substantiate of technical and technological solutions for water regulation on the drained lands in the conditions of climate change. The object of the study is the Danube rice irrigation systems in Odessa region, design, natural and reclamation conditions of which are typical for the most of rice systems in Ukraine. 
 Results of the study and the main conclusions. During the computer experiment the conditions of total evaporation formation were investigated, the water needs of different types of interplanted crops of rice crop rotation were determined for the technology and regime of water regulation on the irrigated lands of rice systems for the typical groups of vegetation periods of target years in view of general heat and moisture provision. Technological efficiency of irrigation of the interplanted crops of rice crop rotation in the variable natural-agro-reclamation conditions of rice system functioning was evaluated and the obtained results with the actual production data were compared. This approach makes it possible to evaluate and predict water needs for irrigation of the interplanted crops of rice crop rotation in the variable natural-agro-reclamation conditions of rice system functioning. 
 Prospects. The obtained results can be effectively used for justification of regime and technological decisions in the projects of reconstruction and modernization of existing rice systems and developing adaptive measures to the predicted climate change in the region.