Incidence of weed seed in cow (Bos sp.) manure and its importance as a weed source for cropland.
Manure samples were collected from 26 New York dairy farms during May-Aug. 1989, and 2 additional farms were sampled over a period of 3 years. A total of 60 samples were collected. Seeds were separated from the manure in a 4-stage process and identified. In 36 manure samples from 20 farms, apparently viable seeds from 13 grasses and 35 broadleaved plants were found. Common lambsquarter (Chenopodium album) was found in manure from more than half of the farms, and yellow foxtail (Setaria glauca), common chickweed (Stellaria media), dandelion (Taraxacum officinale), wild mustard (Brassica kaber [Sinapis arvensis]), redroot pigweed (Amaranthus retroflexus) and barnyard grass (Echinochloa crus-galli) were discovered in manure from 35, 30, 30, 25, 25 and 25%, resp., of the farms sampled. Only 4 farms had manure which contained no seeds at all; the remainder averaged 75 100 per 1000 kg manure. It was concluded that, when compared to soil seedbank numbers, manure is not an important seed source for New York dairy farms. However, problems may arise if imported feeds heavily infested with weed seeds or containing even small numbers of noxious weeds are used.