Two urgent problems of land reclamation under conditions of the Black Sea coast in Ukraine are clearly defined: the development of cultivation technologies of major crops of irrigated crop rotations aimed at rational use of irrigation water, and the utilization of drainage waste waters of rice system to prevent their dumping into recreational ponds – the recreation area of the Black and Azov Seas. The purpose of research is the study of the quality of drainage discharges and the possibility of their mixing with the Dnieper water (good quality), rice and corn response to the quality of irrigation water. While studying the quality of the Dnieper, mixed water (Dnieper – 75 % + of drainage discharges – 25 %) and drainage discharges it was found out that mineralization (dry solid) of drainage discharges and mixed water is higher as compared with the Dnieper water by 83.3 % and 23.2 %, respectively. The mixed irrigation water is less aggressive than that of drainage discharges. Sulphates are by 14.6 % more than in the Dnieper water ,chlorides – 9,8 %, Ca – 6.8 %, Mg – 20,8 %, K + Na – 9.1 %. Drainage discharges are more aggressive than mixed water: they contain 1.5 times more SO4, 1.3 times more Cl, 1.7 times more Mg and 1.2 times more K + Na. The results of field experiments confirmed the possibility of diluting the Dnieper water with drainage discharges in the ratio of 3 : 1. The reduction of the early maturing rice yield by mixed water irrigation was not significant as compared to the use of Dnieper water irrigation and was 0.45 t/ha, or 4.9 %; middle-riping varieties – 0.49 t/ha, or 5.1 %. The irrigation water requirement in both cases was the same, and did not depend on the quality of irrigation water. The results of pot experiments, in which the mixed water is represented by further dilution of the Dnieper water with drainage discharges (1 : 1; 1 : 3), confirm the need to study the feasibility and rationality of larger dilution of drainage discharges when watering rice and related crops of rice crop rotation, that will contribute to environmental protection.
Keywords: drainage waste discharges, rice system, water salinity, nutrients, harmful substances, rice yield, consumptive water use.
