The Impact of Anthropogenically-Controlled Factors on the Formation of Root Mass and Rice Yield under Drip Irrigation in the Lower Volga Region

The results of 3-year studies on the influence of water and nutrient regimes of the soil on the formation of the root system of aerobic rice cultivated with a drip irrigation system are presented. It was shown that, when maintaining the water regime of the soil at not lower than 80% HB in the 0.6-m layer, the root mass is 4.96 in the 0.4-m layer and 5.64 t/ha in the 0.6-m layer. In variant two, where soil moisture was maintained at 80% HB until the end of the tillering phase in the 0.4-m layer and from the booting phase to grain ripening in the 0.6-m layer, the plants were characterized by maximum foliage and habitus, which contributed to an increase in their root mass in the 0.4-m layer to 5.40 t/ha and to 6.14 t/ha in the 0.6-m layer. In variant three, where the water regime of the soil was maintained at 80% HB in the 0.4-m layer from sowing to the end of the tillering phase, then in the 0.6-m layer, and from wax to full ripeness of grain at 70% HB, the root mass was less than in variant two by 0.18 t/ha in the 0.4-m layer and by 0.20 t/ha in the 0.6-m layer but greater than in variant one (80% HB during the entire life cycle) by 0.26 in the 0.4-m layer and by 0.30 t/ha in the 0.6-m layer. Fertilizer doses also had a great effect on the root system of plants. Thus, the root mass was minimal (5.46 t/g) when N 95 P 62 K 75 (5 t/ha) was introduced, while it increased in the N 114 P 74 K 90 variant (6 t/ha) by 0.48 t/ha compared to the value at a dose of N 95 P 62 K 75 (5 t/ha) and was less than when introducing N 137 P 90 K 108 (7 t/ha) by 0.60 t/ha. The maximum grain yield (6.95 t/ha) was obtained at the soil water regime of 80% HB in the 0.4-m and 0.6-m layers when introducing N 137 P 90 K 108 (7 t/ha), and the minimal grain yield (4.88 t/ha) was obtained at the soil water regime of 80% HB in the 0.6-m layer when introducing N 95 P 62 K 75 (5 t/ha).