Productivity of soybean varieties under different irrigation regimes

Abstract. World soybean acreage increases by 3 million hectares annually with average yield of 2.7 t/ha. Significant growth of soybean production in Russia is constrained by increased climate aridization and a declining yield of up to 1.5 t/ha. An important factor in intensification of soybean production is to expand its crops under irrigation. Introduction of adapted and high-yielding varieties of regional selection, followed by improvement of crop water supply, increases yields up to 3…4 t/ha. Soybean varieties selected by Russian Research Institute of Irrigated Agriculture and admitted to production in the Lower Volga region: VNIIOZ 86 (since 2002), VNIIOZ 31 (since 2011), Volgogradka 2 (since 2020) were studied. The experiments were conducted at Russian Research Institute of Irrigated Agriculture in 2013-2015. The experiment included two factors: factor A - varieties, factor B - irrigation regime (70-80-70 % of FMC, 80-80-70 % of FMC and control - 80-80-80 % of FMC). Plots of the 1st (600 m2) and 2nd (200 m2) order were sown in 4-fold replication by a wide-row method (0.7 m) in mid-May with a planned yield of 2.5…3.5 t/ha (N90P90K60 a. i./ha). Soybean varieties differed in peculiarities of crop structure formation. Differentiated irrigation regime resulted in more cost-efficient water consumption followed by yield increase compared to the control. The highest yields were formed by Volgogradka 2 variety (2.87…3.23 t/ha) and VNIIOZ 31 (2.82…3.19 t/ha), which was significantly higher than in VNIIOZ 86 variety (2.17…2.51 t/ha). The variable irrigation regime led to yield increase in all soybean varieties, especially in Volgogradka 2 - by 0.31…0.36 t/ha (10.8…12.5 %) as compared to the control. It was due to grain increase to 30.9…36.2 % in the total biomass compared to the control values - 26.6…27.5 %. The highest amount of post-harvest plant residues (stems, leaves and roots) remained after harvesting Volgogradka 2 (6.39…7.63 t/ha) and VNIIOZ 31(6.73…7.9 t/ha), which improved soil fertility well, and the smallest amount was after VNIIOZ 86 variety (4.41…5.66 t/ha). Differentiated irrigation regime led to decrease in vegetative mass in soil - 4.41…7.42 t/ha compared to the control (5.66…7.9 t/ha). Thus, Volgogradka 2 and VNIIOZ 31 can be recommended for irrigated agriculture in the Lower Volga region, as they provide high yields under differentiated (relatively cost-efficient) irrigation regime and improve soil fertility due to large biomass remained in soil after harvesting.