Effect of Windrow Composting on Weed Seed Germination and Viability

Feedlot manure, containing seeds of twelve weed species, was composted in a windrow to determine whether composting would kill the weed seeds. The twelve species of weeds included: Thlapsi arvense, Polygonum convolvulus, Avena fatua, Chenopodium album, Setaria viridis, Galeopsis tetrahit, Polygonum persicaria, Amaranthus retroflexus, Kochia scoparia, Galium aparine, Malva rotundifolia, and Matricaria perforata. The windrow was managed to maintain core temperatures between 55°C and 65°C for as long as possible.After two weeks of composting, seeds of Galium aparine, Setaria viridis, Kochia scoparia, Matricaria perforata, Thlapsi arvense and Polygonum convolvulus had 0 percent viability in a tetrazolium test. Seeds of Amaranthus retroflexus had a viability of 3.5 percent, the highest of the twelve species studied. After four weeks of composting, the viability for all twelve species was 0 percent. Therefore, seed viability was extremely low after even two weeks of windrow composting and four weeks of composting was enough to kill all seeds of the twelve species studied.