Grass–Legume Mixtures Suppress Weeds during Establishment Better than Monocultures

Abstract

Maintaining a diversity of plant species in pastures may reduce weed invasion. Knowledge of how the proportion of species in a mixture (i.e., species evenness) aff ects weed invasion would be useful in formulating seed mixtures. We hypothesized that forage mixtures with greater species evenness would reduce weed invasion at establishment better than mixtures dominated by a few species (low species evenness) or monocultures. Fift een mixtures and monocultures of orchardgrass (Dactylis glomerata L.), quackgrass (Elytrigia repens L.), alfalfa (Medicago sativa L.), and white clover (Trifolium repens L.) were sown in autumn 2008 at four locations in Pennsylvania and Wisconsin. Th ere were four monocultures, four mixtures dominated by one species (evenness = 0.64), six mixtures dominated by pairs of species (evenness = 0.88), and one equal mixture (evenness = 1). We measured the amount of naturally occurring weeds in harvested herbage at each location in 2009. At two locations, we added seed of plumeless thistle (Carduus acanthoides L.) and canola (Brassica napus L.; a surrogate weed) to each treatment during autumn of 2008 and measured their establishment and dry mass during 2009. Grass-legume mixtures resisted weed invasion better than monocultures. Within mixtures, however, species evenness did not infl uence weed invasion. Species evenness did not aff ect resource use (light interception or soil inorganic N levels). Individual forage species had a strong eff ect because weed proportions decreased curvilinearly as orchardgrass proportion of the seed mixture increased. Selecting appropriate species to use in mixtures is more important than the evenness of the species in the mixture.

Effect of applied cultivation technology and environmental conditions on lucerne farm yield in the Central Europe

“…From all management methods, only lucernegrass mixture significantly increased forage yield in accordance with the positive effect of mixture to dry matter yield (Bélanger et al 2014). Grass legume mixtures also resist weed invasion better than monocultures (Sanderson et al 2012), however some changes in forage nutritive value could be also observed (Bélanger et al 2014). In the Czech Republic, this technology is more applied in more humid regions (CR 5: 7.5°C, 600 mm; CR 7: 6.5°C, 700 mm) which are more favourable for grass components.…”

Diversification and ecosystem services for conservation agriculture: Outcomes from pastures and integrated crop–livestock systems

“…Weed abundance was inversely related to the evenness (evenness is a measure of the relative distribution or proportion of plant species in a community) of forage species in clipped plots and on-farm surveys of plant species diversity in pastures 16,43 . In research designed to control for species evenness, however, there was no evidence that evenness of grass-legume mixtures affected weed invasion 44 . Species composition of the mixtures, however, had a strong effect on invasion, indicating that selecting the appropriate species in mixtures to achieve a specific function is more important than evenness of the species in the mixture.…”

Promising options for improving performance and proanthocyanidins of the forage legume sainfoin (Onobrychis viciifolia Scop.)

“…While weed control through herbicides is cost-intensive and may have undesired 164 environmental effects, grass-legume mixtures offer the possibility to significantly decrease the 165 6 invasion of unsown species in mixed stands (Connolly et al 2017; Sanderson et al 2012). However, 166 in sainfoin some partner species were found not only to considerably suppress weed infestations, but 167 also lead to a drastically reduced sainfoin yield when compared to monoculture (Häring et al 2008).…”