Effects of composted swine manure on weed seedbank

Giant foxtail, common lambsquarters, common waterhemp, and Pennsylvania smartweed comprised 99.5 and 80.7% of seeds detected in the seedbank and compost, respectively. Between 1 ± 1 and 169 ± 48 weed seeds m−2 of soil surface (mean ± S.E.M.) were incorporated through compost amendments, the mean number of viable seeds in the compost being less than 8 seeds m−2. Weed seed density in the seedbank ranged from 0 ± 0 to 26,662 ± 8683 seeds m−2 to a depth of 10 cm. Compost did not modify seed abundance, but there was a species-specific response to year of study and crop sequence. Weed seed longevity and seedling emergence were not affected by compost, but more seeds were recovered with a higher viability in 2000 than in 2001. These results indicate that use of composted swine manure represents a small risk to directly increase weed seed abundance in the seedbank.