Preharvest glyphosate in alfalfa for seed production: Effect on alfalfa seed yield and quality

Abstract

. 2003. Preharvest glyphosate in alfalfa for seed production. Effect on alfalfa seed yield and quality. Can J. Plant Sci. 83: [189][190][191][192][193][194][195][196][197]. Preharvest applications of glyphosate have been shown to be effective in controlling Canada thistle in annual crops, but may reduce alfalfa seed yield depending on time and rate of application. The objective of this study was to determine the effect of preharvest applications of glyphosate on subsequent alfalfa seed yield and quality. The effects of timing, 1, 26, 51 and 76% alfalfa seed pod maturity, and rate, 0, 440, 880, 1320, and 1760 g a.i. ha -1 , of a preharvest application of glyphosate on alfalfa seed yield and quality in the year of application, and regrowth and seed yield in the following year were determined. The rate of glyphosate applied did not affect seed yield in the application year; however, in the following year, growth and seed yield were reduced as rates increased. Delaying the application of glyphosate increased seed yields in the application year, but decreased alfalfa regrowth and flowering the following year. Germination and seedling emergence were not affected by the rate or timing of the glyphosate. A preharvest application of glyphosate at 1760 g a.i. ha -1 at 76% pod maturity is a viable option in the last year of seed production. [189][190][191][192][193][194][195][196][197]. L'application de glyphosate avant la récolte semble donner de bons résultats dans la lutte contre le chardon des champs pour les cultures annuelles, mais cette méthode pourrait réduire le rendement grainier de la luzerne, selon le taux d'application et le moment du traitement. L'étude devait établir l'incidence de l'application de glyphosate avant la récolte sur le rendement grainier et la qualité des semences de la luzerne. Les auteurs ont déterminé les effets du moment du traitement (à 1, 26, 51 et 76 % de maturité des gousses) et du taux d'application (0, 440, 880, 1 320 et 1 760 g de matière active par hectare) sur le rendement grainier et la qualité des semences de la luzerne l'année du traitement ainsi que leurs effets sur la repousse et le rendement grainier l'année suivante. Le taux d'application n'agit pas sur le rendement grainier l'année du traitement, mais l'année suivante, la croissance et le rendement grainier diminuent avec la hausse du taux d'application. Quand on retarde l'application du glyphosate, le rendement grainier augmente l'année du traitement, mais la repousse et la floraison sont plus faibles l'année suivante. La germination et le taux de levée ne sont pas affectés par le taux d'application ni par le moment du traitement. L'application de 1 760 g de glyphosate par hectare avant la récolte, lorsque 76 % des gousses sont parvenues à maturité, est une solution envisageable la dernière année de récolte des graines.

Preharvest glyphosate in alfalfa for seed production: Control of Canada thistle

“…At all test locations, the alfalfa seed yield in the year of application was not reduced by glyphosate application, regardless of the rate. These results agree with those of Packer and Krall (1989) and May et al (2003). Dawson (1992) reported a yield decrease in the year of application; however, the percentage of pod maturity when the glyphosate was applied was not reported.…”

“…However, seedling emergence was not affected by the glyphosate. Similar results were obtained in a parallel study conducted at the Melfort Research Station where germination and emergence were not affected by the rate of glyphosate applied to the alfalfa (May et al 2003).…”

Desiccation, postharvest maturity and seed aging of tall oat-grass

“…Similar results on desiccation effects at different stages of maturation on wheat seed germination were reported by Yenish & Young (2000). However, desiccation applied in various maturity stages of alfalfa seeds did not show a significant effect on germination (May et al, 2003). According to the Pearson's coefficient of correlation, the dependence between seed yield and the 1,000-seed weight was positive and significant, but rather low (r = 0.327; p≤0.05), while the association between yield and final germination was also positive but not significant (r = 0.151).…”

Perennial Grain Legume Domestication Phase I: Criteria for Candidate Species Selection

“…Ideally, selection candidates that undergo a programmed senescence corresponding to seed maturation could be identified or easily selected; however, that may be unlikely and other strategies should be identified. Seed production of many perennial forage legumes requires precutting or plant desiccants to aid in "drying down" the plant prior to mechanical harvest [63,64], but the extra field pass and the use of chemical inputs should be avoided if possible. Candidate species with terminal racemes which extend above the leaf canopy, as opposed to axillary racemes, could allow for mechanical harvest by avoiding contact between the cutting machinery and the higher moisture plant material lower in the canopy.…”