Changes in the soil seed bank of four long-term crop/herbicide experiments.
Abstract
The numbers of viable weed seeds in the top 15 cm of the soil were determined over a 16-year period in 4 crops grown with or without herbicides and hoed or hand-weeded. The numbers of viable seeds of Aphanes arvensis, Raphanus raphanistrum, Chrysanthemum segetum, Arabidopsis thaliana, Papaver rhoeas, Viola arvensis and Trifolium repens declined progressively irrespective of treatment. Changes in other species reflected opportunities for seed production. After 16 years, the principal species in spring wheat and barley (with or without tri-allate or MCPA) were Polygonum aviculare, Stellaria media and Poa annua, in maize (with or without simazine) were Solanum nigrum and Urtica urens and in carrots (with or without linuron) were P. annua and Capsella bursa-pastoris. Herbicides had little qualitative effect on species composition but in maize and carrots the final populations where herbicides had been used were much lower than on untreated plots. See also WA 20, 1863.