The paper studies the influence of sowing time on the main indicators of photosynthesis of soy corps in conditions of Fore-Caucasus. The highest biological yield of dry biomass was accumulated by the breeds after the first sowing period (6.92 t/ha for Zernogradskaya 2, 7.55 t/ha for Selekta 201 and 8.16 t/ha for Renta). The breeds have the highest net photosynthesis productivity was noted for the first two sowing periods. The third sowing period falls behind for this indicator by 5–6 %. Renta breed in terms of the quantity of dry biomass generated during one day calculated for the area of leaves of one square meter had a significant advantage. The highest crop productivity of studied breed was noted after the first sowing period. The productivity of the seeds was as follows: 1.93 t/ha for Zernogradskaya 2, 2.14 t/ha for Selekta 201 and 2.39 t/ha for Renta. In terms of the coefficient of the business efficacy of soy, the first sowing period is the best one.