Photosynthetic activity of soybean crops in response to different sowing times under the environmental conditions of the Russian Far East

Abstract

The aim of this study was to determine the optimal sowing time for photosynthetic activity in the soybean varieties «Batya» and «Khabarovskiy Yubilyar» in the Russian Far East. We studied the influence of several parameters that induce photosynthetic activity on the productive qualities of soybean seeds from these varieties at different sowing dates. Studies have shown that the factor which most significantly determines biological productivity is leaf area. Here, leaf area accounted for 92.3% of the total productivity, with 77.3% depending on the photosynthetic potential of the soybean plants. Optimal conditions for the growth of soybean leaves and the duration of their function were created during the May sowing dates. The leaf area of «Batya» and «Khabarovskiy Yubilyar» varieties decreased by 6–36% and 11–27%, respectively, at later sowing dates. The lowest net photosynthetic productivity in «Batya» was 2.0 g/m2/day during the late sowing period, and the maximum value recorded was 4.2 g/m2/day when sowing was at the end of May. The lowest photosynthetic productivity for the variety «Khabarovskiy Yubilyar» (3.4 g/m2/day) was also recorded in plants from the late sowing period.