Weed infestation of switchgrass (Panicum virgatum L.) crops

Abstract

Purpose. Determination of the species composition of weeds in switchgrass crops and their influence on the formation of biomass productivity. Methods. Field, laboratory, quantitative-weighing, calculation-comparative, mathematical-statistical. Results. The results of studies on weed infestation of switchgrass crops and methods of their control are highlighted. A mixed type of weediness was observed in the crops, consisting of 19 species from 8 families, with a predominance of annual dicotyledonous species (75.0-87.2%). While in the third (91.7-95.1%) and fifth (61.0-91.7%) years of vegetation, perennial dicot species such as Erigeron canadensis, Lactuc aserriola L., Artemisia annua L., thistles ones, annual dicotyledons were not present. When analyzing the quantitative composition of weeds in the first year of vegetation on the weedy control, high level of weed infestation was observed, which amounted to 176 pcs./m2, in the second and third years 103-105 pcs./m2, in the fourth – 74 pcs./m2 and in the fifth – 39 pcs./m2 . In the variants where weed control was used in the third and subsequent years a decrease in the number of weeds by 83.5-88.4% was noted compared to the control. The use of herbicides on crops ensured efficiency in the first year of vegetation at the level of 72.3-76.9%, while in the fifth year it was 95.3-96.2%. Weed control allowed increasing the biomass yield to 10.7-10.8 t/ha, while the weeded control yielded 8.8 t/ha. Conclusions. The use of herbicides (Dialen super 464 SL, Caliber 50) led to a decrease in the number of weed plants from 28.6% in the first year of vegetation to 88.3% in the fifth year, providing a 72.3-97.6% efficiency depending on the year of vegetation of the crop. Weed controll in the fifth year of crop vegetation made it possible to obtain 11.0 t/ha of dry biomass, 11.9 t/ha of solid fuel, 220 GJ/ha energy from fuel.