Fate of weed seeds in spent mushroom compost following commercial mushroom production

Abstract

Abstract Commercial mushroom producers grow several varieties of mushrooms on compost. Upon completion of the growing cycle, the spent mushroom compost is often sold as a soil amendment for both agricultural and homeowner use. Mushroom compost ingredients often come from fields infested with weeds, and in turn compost may spread unwanted weed seed. We conducted studies to assess the viability of weed seed following specific stages of the commercial mushroom production process. Weed seed was more likely to survive if the entire production process was not completed. However, no viable hairy vetch, Italian ryegrass, ivyleaf morningglory, Palmer amaranth, or velvetleaf remained at the end of the study. Although the seeds of most species were eliminated earlier in the composting process, ivyleaf morningglory required the complete process to eliminate 100% of the seed. These results indicate that spent mushroom compost is free of many weed species upon removal from mushroom houses and is unlikely to spread weed seed. Nomenclature: Hairy vetch, Vicia villosa Roth; Italian ryegrass, Lolium multiflorum Lam.; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq.; Palmer amaranth, Amaranthus palmeri S. Wats.; velvetleaf, Abutilon theophrasti Medik.; mushroom, Agaricus bisporus