JUSTIFICATION OF WATER REGIME AND IRRIGATION REGULATIONS FOR AEROBIC RICE

Abstract

Taking into account that rice belongs to the plants that form the fibrous root system the article defines the need to selection of varieties growing on unsaturated with water soil. Such a so-called aerobic rice variety has been obtained in the All-Russian Research Institute of Irrigated Agriculture. The results of the substantiation of an effective water regime on this variety sowings and the irrigation regulations are presented. Sowing was conducted by seeder under the soil warming up to 140С in 2013 and 2014 – April, 28 and 2015 – May, 8. For watering was used a drip irrigation system. The drip lines were laid every 0.6 m, the distance between the droppers was 0.33 m, the water supply through the dropper was 2.2 l / h. The soil of the experimental site is light chestnut, the humus content is 1.6 - 1.8%, the density of natural composition for the calculated layers of 0.4 and 0.6 m is 1.27 and 1.29 t / m3 respectively, the lowest moisture capacity is 24.9 and 23.8% of dry soil mass. Porosity indices for layers varied from 46.64 to 51.59%, solid phase density - from 2.52 to 2.72 t / m3. According to the provision of precipitation for the growing season 2013 is characterized as wet (306.9 mm), 2014 – medium dry (104.9) and 2015 – medium moisture (235.4 mm). The scheme of the two-factor experiment included three options for the water regime of the soil: A1 (control) – reducing the moisture content of the active layer (0.6 m) of the soil to 80% of minimum water capacity; A2 – according to option A1 until the end of the rice tillering phase in 0.4 m layer with following an increasing in the layer to 0.6 m; A3 – water regime according to the A2 option until the beginning of the grain wax ripeness with a decrease in the pre-irrigation moisture content to 70% of minimum water capacity. The second factor included the doses of fertilizers: B1 – to obtain a grain yield of 5 t / ha (N109P62K75); B2 - 6 t / ha (N131P74K90) and B3 – 7 t / ha (N151P90 K108). The supply of irrigation water in the amount of irrigation rates was controlled by the duration of irrigation, determined by the water flow through the droppers, as well as by the reads of the water meter installed on the experimental site. The timing of irrigation was determined by reducing the impact to the pre-irrigation level. With short duration of irrigation intervals (2-4 days) with bioclimatic and at least twice a month, as well as when sowing and ripening grain with thermostatic-weight. Operational control over soil dynamics was also provided by a calibrated moisture meter AQVATERR T - 350. The irrigation water consumption with a rice yield of 5-7 t / ha of grain according to three-year studies in the drip irrigation system varied from 4920 to 5357 m³ / ha, this is 4 - 6 less compared to existing flood irrigation technology. The research was carried out in 2013-2015 at the All-Russian Research Institute of Irrigated Agriculture.