Publication Date
1989
Description
Self-regenerating annual legumes, including subterranean clover and medics (Medicago spp.) are important pasture species in the cereal-livestock production zone of southern Australia and other Mediterranean climatic zones of the world. The pattern of germination in the genus Medicago, in which only a small percentage of seed germinates at one time because of hard-seededness has many ecological advantages particularly for the successful dissemination and colonization of medics. When medic pastures are incorporated into rotation systems with field crops the hard-seededness trait enables the medic seed population in the soil to survive periods of one, two or possibly three or more years of cropping without seed reserves being replenished. Cereal straw residues have been shown to cause substantial reductions in the density of self-regenerating annual medics (Quigley and Carter, 1985). Vegetative ground cover over summer is known to influence the breakdown of hardseededness in annual legumes (Quinlivan and Millington, 1962; Burton, 1964) thus affecting the density of seedlings which regenerate in autumn. However, this relationship has not been researched in detail and quantitative data on the effects of shading by stubble on germination of seed is limited. The location of seed within the soil profile would affect diurnal temperature variation which controls the rate of change of seedcoat permeability. Effects of depth of burial of seed in soil have been examined by Burton (1964) and by Taylor (1984, 1985) with subterranean clover. In view of the marked differences in the patterns of seed softening for medics and subterranean clover the deficiency in our knowledge of distribution of medic seed in soil profiles and the relevance of this to breackdown of hard-seededness is most serious : however, some data has recently been obtained by Quigley et al. (1987). This paper presents detailed information on the harmful effects of thermal insulation, either by straw residues or cover by soil, on levels of hard-seededness in barrel medic (Medicago truncatula).
Citation
Quigley, P E. and Carter, E D., "Effects of Straw Cover and Seed Burial on Changes in Hard Seededness of Annual Medics" (2025). IGC Proceedings (1989-2023). 28.
https://uknowledge.uky.edu/igc/1989/session13b/28
Included in
Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Effects of Straw Cover and Seed Burial on Changes in Hard Seededness of Annual Medics
Self-regenerating annual legumes, including subterranean clover and medics (Medicago spp.) are important pasture species in the cereal-livestock production zone of southern Australia and other Mediterranean climatic zones of the world. The pattern of germination in the genus Medicago, in which only a small percentage of seed germinates at one time because of hard-seededness has many ecological advantages particularly for the successful dissemination and colonization of medics. When medic pastures are incorporated into rotation systems with field crops the hard-seededness trait enables the medic seed population in the soil to survive periods of one, two or possibly three or more years of cropping without seed reserves being replenished. Cereal straw residues have been shown to cause substantial reductions in the density of self-regenerating annual medics (Quigley and Carter, 1985). Vegetative ground cover over summer is known to influence the breakdown of hardseededness in annual legumes (Quinlivan and Millington, 1962; Burton, 1964) thus affecting the density of seedlings which regenerate in autumn. However, this relationship has not been researched in detail and quantitative data on the effects of shading by stubble on germination of seed is limited. The location of seed within the soil profile would affect diurnal temperature variation which controls the rate of change of seedcoat permeability. Effects of depth of burial of seed in soil have been examined by Burton (1964) and by Taylor (1984, 1985) with subterranean clover. In view of the marked differences in the patterns of seed softening for medics and subterranean clover the deficiency in our knowledge of distribution of medic seed in soil profiles and the relevance of this to breackdown of hard-seededness is most serious : however, some data has recently been obtained by Quigley et al. (1987). This paper presents detailed information on the harmful effects of thermal insulation, either by straw residues or cover by soil, on levels of hard-seededness in barrel medic (Medicago truncatula).
