Physiological Responses of Cucumber Plants to Application of Sodium Lignosulfonate on Sandy Loam Soil

The issue of using lignosulfonates (LSs) to improve soil fertility is currently under discussion. The effect of the sodium LS application on the accumulation of biomass, photosynthesis, respiration, and their ratio in cucumber plants was studied. The application of LS at 10–25 g/kg did not have any significant effect on the studied parameters of the physiological state of plants. However, the growth rate and activity of the photosynthetic apparatus decreased at a high content of LS in the soil (50–100 g/kg) and the rate of respiration increased resulting in an increased ratio of respiration to photosynthesis. High concentrations of LS in the soil negatively affected the physiological state of the cucumber and its resistance to cold, which is explained presumably by sodium salinization of the soil.