EFFETS DES TEMPERATURES DU SOL, DES DATES DE SEMIS ET DES MAUVAISES HERBES SUR LES COMPOSANTES DU RENDEMENT DE L’AVOINE

Abstract

On a St-André sandy loam and on a Kamouraska clay, the effect of soil temperature on oats (Avena sativa L.) was measured in the greenhouse using a system described by Deschênes et al. in 1974 and in the field, using two dates of seeding. The effect of weeds was measured by using un weeded and hand-weeded treatments. In the greenhouse, cool soil temperatures have delayed maturity and decreased straw and grain yields as well as total phytomass of oats on the two soil types. The dry weight of weeds in un weeded pots increased slightly. The effect of hand-weeding on oats was especially noticeable on the St-André sandy loam where three times as many weeds were observed. The straw yield and the total phytomass of oats were higher in the field experiment following an early seeding of oats on both soil types. On the other hand, grain yield was lower on plots seeded early and located on St-André sandy loam while the opposite was true on Kamouraska clay. The dry weight of weeds was lower on unweeded plots seeded early. The weeds reduced straw and grain yields on the St-André sandy loam but had no effect on Kamouraska clay because of the low weed infestation on the latter. The greenhouse and field experiments suggest that soil temperature is not the main factor in explaining the increase in grain yield observed with early-seeded cereals.