LONGEVITY OF CROP AND WEED SEEDS: SURVIVAL AFTER 20 YEARS IN SOIL

Summary. Results are presented of a 20‐year investigation into survival of crop and weed seeds in undisturbed soil. Indications are that seeds reveal their survival potential during the first 4 years; only rarely did species which persisted for this initial period lose all viability in the subsequent 16 years. Deterioration occurred more rapidly in acid peat than in loam soil, and the species which persisted in peat also remained viable in loam soil. The Gramineae were short‐lived in the soil, with the exception of Phleum spp., some seeds of which persisted for 20 years. Most leguminous species persisted for the whole period but not to the same extent as some of the weed species. Of the weeds, the species with the highest percentage seed survival were Ranunculus repens (53%), Chenopodium album (23%) and Rumex crispus (18%). Longévité des semences de plantes cultivées et de mauvaises herbes: survivance après 20 années dans le sol