Potential of industrial hemp (Cannabis sativa L.) genotypes to suppress weeds

Abstract

Field experiments designed to explore weediness of hemp crops of industrial varieties were carried out at the Upytė Experimental Station of the Lithuanian Research Centre for Agriculture and Forestry in 2010-2012. Eight monoecious industrial hemp varieties from France (5), Poland (2) and Ukraine (1) were grown in a conventional crop rotation after winter wheat. Hemp was sown at a seed rate of 50 kg ha -1 with 10 cm interrows at the beginning of May and harvested when the first matured seeds appeared. No mechanical or chemical weed control was applied during hemp growth period. Density of weeds at full hemp emergence was relatively high, with the highest average value of 202 plants m -2 in 2011, the year with relatively high air temperatures at the end of May -beginning of June and adequate rainfall. At hemp harvesting, the highest weed density and above-ground biomass was found in 2010, the year characterised by high temperatures in July and August, in the plots of the USO 31, the variety with the shortest growth period and the lowest plant height. A total of 31 weed species were identified in hemp experiments -26 species of broad-leaf and grass weeds and 5 species of perennial weeds. At full hemp emergence, weeds typical of spring crops of the region were most abundant: Chenopodium album L. dominated in 2010, Veronica arvensis L. in 2011, while in 2012 the domination was shared by the four weed species Lamium purpureum L., Thlaspi arvense L., V. arvensis and Poa annua L. At harvest, in total 8 weed species were found; however, only C. album and partly Polygonum aviculare L. were relatively abundant in all years.

Investigation of hemp (Cannabis sativa L.) crop weediness

“…Hemp crop weediness at harvesting time was much lower than that at the beginning of vegetation (Tables 5 and 4), but still abundant (12-23 plants m -2 ). Similar amount was found at harvest in previous our investigations [20]. Perhaps, rainy period was favourable not only for hemp growing, but for weeds as well.…”

Effect of Fertilization and Weed Management on Weed Flora of Hemp Crop

“…Comparable results were reported byCampiglia et al (2017),Papastylianou et al, (2017) andTang et al, (2016) who found that high N fertilization had a positive impact on hemp biomass. In addition, as reported by other studies, cultivars 'Futura 75' and 'Fedora 17' showed higher biomass yield and weed competitiveness compared to the early cultivar 'Uso 31' under contrasting environments and management practices(Sausserde et al, 2013;Jankauskiené et al, 2014;Tang et al, 2016).…”

“…As a result, the opinion that weed control in hemp is usually unnecessary, specially under high crop densities, has been expressed by a number of researchers (Struik et al, 2000;Campiglia et al, 2017). However, other studies suggest that weed control is essential for high crop yields when hemp is grown for seed or at low plant densities (Jankauskiené et al, 2014;Flessner et al, 2019). Although these latter studies provide indication that weed infestation in early crop growth can cause severe yield losses in hemp, information on crop interaction with weed communities of local agro-ecosystems under different types of cultural management is very scarce (Sandler and Gibson, 2019).…”

A call for weed research in industrial hemp (Cannabis sativa L)

“…Jankauskien≐ et al . () evaluated the potential suppression of weeds by eight monoecious hemp cultivars in Lithuania and reported relatively high weed densities (133–202 plants m −2 depending on year) that the authors hypothesised stemmed, in part, from environmental conditions. At hemp harvest, greatest weed densities existed in plots with cultivars USO 31, the variety with the shortest growth period and plant height, and Beniko, a variety considered to mature early, and the authors suggested that early flowering could potentially limit canopy development and, therefore, the ability of the crop to suppress weeds (Jankauskien≐ et al ., ).…”