Weed infestation of switchgrass crops as affected by the plant density

Abstract

Purpose. To study the competitive relationship between the plants of switchgrass (Раnісum virgatum L.) and weeds as affected by the plant density under the conditions of the Right Bank Forest-Steppe of Ukraine.Methods. Field, laboratory.Results. The following species of weeds were found in switchgrass crops: Chenopodium album, Galinsoga parviflora, Persicaria lapathifola, Amaranthus retroflexus, Xanthium strumarium, Melandrium album, Thlaspi arvense, Sinapis arvensis, Echinichloa crus-galli and Setaria glauca. At the time of accounting, the highest weed density (plant/m2) was found in the variants with plant density (plants/m2) of 50 and 100. In particular, the number of annual cereal weeds in these variants was 57.9 and 35.8, Thlaspi arvense 23.6 and 10.4, Amaranthus retroflexus 22.4 and 10.7, Galinsoga parviflora 21.7 and 9.1, Sinapis arvensis 21.4 and 9.9, Chenopodium album 18.5 and 9.9, Persicaria lapathifola 9.8 and 5.3, respectively. The total number of weeds in the variant with a density of 50 was 188.2, which is 34% more compared to the variant where switchgrass density was 200. Under conditions of joint vegetation with weeds, switchgrass fomed rather insignificant vegetative mass. In particular, for the switchgrass density of 50, only 23.0 g of crop mass per m2 was recorded, whereas the weeds generally formed the maximum experimental values of 2288.8 g/m2. For the cultivation of switchgrass at a density of 100, its green mass was 34.0 g/m2, while that weeds was 1088.7 g/m2, which is 2.1 times less compared to the previous variant. For the density of 150, switchgrass green mass was 58.0 g/m2, and the maximum density (200) 73.0 g/m2. In these variants, biomass of weeds decreased to 780.1 and 569.8 g/m2, respectively.Conclusions. The intensity of weed dry mass accumulation in switchgrass stands drastically decreased with increasing the density of switchgrass in the experiment from 50 to 100 plants per m2. At the same time, full dominance of switchgrass in the stands in the first year of vegetation, even at the plant densities of 150 and 200 plants per m2, was not observed. In particular, the maximum weed density generally formed a dry mass of 254.8 g/m2, while the plants of switchgrass formed only 35.6 g/m2.