Weed effects on the establishment and nutritive value of pastures with different annual/perennial ratio.

LAVARELLO HERBIN, AGUSTINA; GOLLUSCIO, R.; RODRIGUEZ, A

Agrosystems, Geosciences & Environment

Wiley

Lugar: Londres; Año: 2020 vol. 3

2639-6696

Livestock intensification is increasing weed invasion in pastures. We performed anexperiment near Buenos Aires, Argentina, to evaluate the impact of weeds on temperatecultivated pastures. We sowed 1,700 viable seeds m?2 in 24, 1.5-m2 plots.Each plot had seven sowed lines, three of legumes (red clover, Trifolium pratense L.;50% of seeds) alternating with four of grasses arranged in two sowing designs differingin the annual/perennial ratio: 70% prairie grass (Bromus willdenowii Kunth, Bw,annual species) + 30% of orchardgrass (Dactylis glomerata L., Dg, perennial species)(>Bw), or 30% of Bw + 70% of Dg (>Dg). In the inter-lines of each plot, we sowedtheweed brownmustard (Brassica juncea L.) at four growing densities.At 123 d aftersowing, we harvested aerial biomass of weeds and forage species (legume biomasswas almost negligible at this date). We quantified aboveground net primary production(ANPP) of weeds and grasses (separated into blades, sheaths, and blades +sheaths), tiller density (indicating potential persistence), blade crude protein (CP),and neutral detergent fiber (NDF) concentrations of grasses.We made regressions toanalyze the direct effect of weed biomass on each grass species, their indirect effectson the proportion of each species in the pasture, and their net effects on both speciestaken together.Weeds had negative direct and net effects. However, they did not haveany indirect effect on species proportion. Pastures with lower annual/perennial ratiowere more productive and potentially more persistent. Weeds also directly increasedblade CP of the annual species.