Using herbicides for sod suppression during pasture renovation by legume sod-seeding often results in the loss of potentially usable forage, weed encroachment, and inadequate legume:grass ratios. Physical sod suppression methods could alleviate some of the problems associated with suppression via herbicide. A study was conducted in Québec, Canada, to investigate, as an alternative to herbicide, sod suppression by sheep grazing or mowing before and after spring no-till seeding of red clover (Trifolium pratense L.) or white clover (T. repens L.). Sod-suppression treatments included six physical suppression methods: mowing or sheep grazing, to 5 or 10 cm, at seeding and when the grass sward reached 30 cm during the first 2 mo of clover establishment, or similarly managed mowing or sheep grazing to 5 cm with an additional defoliation the previous fall. Additional treatments included suppression by herbicide (glyphosate [N-(Phosphonomethyl) glycine] at 2.6 kg a.i. ha–1) and two controls: sod-seeding with no sod suppression and no seeding. Among the physical suppression treatments, grazing and mowing to 5 cm resulted in highest clover densities, similar to those achieved via herbicide suppression. Red and white clover had similar plant densities. Yield components and total forage yields varied with sites. Clover yields tended to be higher with herbicide than under physical suppression treatments. However, increasing the severity of physical suppression increased clover yields. Weed encroachment was observed only with herbicide sod suppression. Unlike suppression with herbicide, physical suppression did not decrease total forage yields in the renovation and post-renovation years when compared with controls. Forage quality was increased in the renovation year by both physical suppression methods and herbicide when compared with unrenovated controls; but the increase was greater with herbicide suppression. Only the most severe of the physical suppression methods sustained increased forage quality in the year after renovation. Timely mowing or grazing as methods for suppression of grass sod during renovation with legumes appear to have potential, but cannot yet be recommended as alternatives to herbicide. Key words: Clover, forage, grazing, pasture renovation, sod-seeding
Evaluation of red clover (Trifolium pratense L.) resistance to Sclerotinia crown and root rot (Sclerotinia trifoliorum) in the laboratory and field conditions
