EMERGENCE AND LONGEVITY IN CULTIVATED SOIL OF SEEDS OF SOME ANNUAL WEEDS

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Abstract
Summary. Four replicated experiments were begun in successive years to study the behaviour of viable seeds of eleven species of annual weeds when mixed with a 3 in. layer of cultivated soil. The soil was confined in pots sunk in the ground outdoors, seedling emergence was recorded, and the numbers of viable seeds remaining at the end of the experiments were assessed. One experiment was continued for 3 years, the others for 5 lull calendar years after the freshly collected seeds had been sown.Initial emergence was greatest with Stellaria media, Senecio vulgaris and Poa annua, and least with Chenopodium album and Thlaspi arvense. Subsequently, the numbers of seedlings which emerged each year declined at a rate which was constant for each species. In the fifth year after sowing, the number of seedlings of Senecio vulgaris was only 0.3% of the initial number of viable seeds, while for Thlaspi arvense and Veronica hederifolia the figure was 3.2%.The proportions of viable seeds which produced seedlings ranged from 37 to 86%, while from 0 to 11% were still present in the dormant state after 5 years. Most species showed marked patterns in the seasonal distribution of emergence which were modified by variations in weather from year to year, but in any one year, the distribution of emergence was not influenced by the length of time the seeds had been in the soil.Germination et longévité dans des sots cultivés de semences de quelques mauvaises herbes annuelles