Stimulation of symbiotic activity and forage productivity in leguminous agrocenoses

Abstract

To develop approaches aimed at improving the sowing and quality characters of legume grass seeds, enhancing their symbiotic activity, and increasing forage production, the studies were conducted to assess the stimulation effect of super-high-frequency electromagnetic field (SHF EMF). Air-dry seeds were exposed to SHF irradiation at a power of 800 W with different exposure duration: 10, 20, 30, 40, 50, 60, and 70 s. The experiments used the varieties of red clover (Trifolium pratense L.) and Hungarian sainfoin (Onobrychis arenaria (Kit.) DC.) adapted to the foothill zones of the North Caucasus. The SHF effect was evaluated by changes in symbiotic activity and forage production compared to untreated control. The highest symbiotic activity and forage production in the investigated legume grasses were achieved with pre-sowing seed activation by SHF EMF at 800 W for 40 s. Under these conditions, symbiotic activity of clover and sainfoin increased due to a rise in the number and weight of active nodules by 12.5–16.9%; herbage weight increased by 60.0–63.7%, and dry matter content - by 10.7–24.3%. The nutritional value of the biomass also improved: the yield of fodder units increased by 1.24–1.27 t/ha, digestible protein - by 0.24–0.27 t ha, and metabolizable energy - by 9.5–10.2 GJ ha. Extending the treatment to 70 s resulted in reduced production which was due to slowed plant development caused by a rapid increase of seed internal temperature; when the threshold values of approximately 50–60°C were exceeded, heat shock might occur.