Weed seed contaminants in cereal seed

The incidence of weed seeds in samples of certified cereal seed tested at the Official Seed Testing Station for Scotland over the last decade is discussed and compared with data from previous surveys and those from tests of precertification seed in 1996/7. Contamination of certified seed is now at very low levels (0.38 seeds per kilogram of certified barley in 1996/7). Legislation and seed cleaning have had a major influence on the overall size of weed seed populations in cereal seed and on the component species of these populations. Significant numbers of weed seeds are however present in pre-certified seed, and the use of uncleaned farm-saved seed could be an important agency for the spread of weeds.