Effect of Windrow Composting on Weed Seed Germination and Viability

Abstract

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: Thfnpsi arvensc, Polygonum comolzwliis, Aiienn fntua, Chenopodium album, Setarin viridis, Galeopsrs tetrahit, Poly,yoiruiri pcrsicorio, Ainnrnnflius retrojlexus, Kochin scopnrin, Gnlium npnrine, Malm rotundrfolm, and Mntrrcnrrn pevfornta. 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 Gnlriirii npnrriie, Sctnrm zvrrdis, Kocliin scoparin, Mntricarin pevforatn, Thlapsi amense and Poly~yoniiin cotivolvulirs had 0 percent viability in a tetrazolium test. Seedsof Amnrnnflius retrt$cwis 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. IntrodtictionThe disposal of cattle manure is a problem for many feedlot operators. Feedlot manure is typically land spread, but this may lead to increased weed problems. For example, Blackshaw and Rode (1991) found that many weed species (including Sctaria viridis, Kochia scoparia, Antaranthus refroflexus, Ckenopodiirnr albtini, Pol!jgonu ttt convolvulus, and Mdva rotzrndifolin) were able to survive rumen digestion. The proportion of the population that was able to survive varied with species.There is a common perception that composting kills weed seeds. However, there has been little documentation of this. A study done in Florida by Shiralipour and McConnell, 1991, reported that certain weed species were killed when placed in a pile of composting yard waste. This only held true when the seeds were exposed to high temperatures within the pile.Egley, 1990, reported that killing temperatures vary inversely with the moisture content of the seed. Consequently, moist seeds within a compost pile should be killed at a lower temperature than dry seeds of the same species. Materials and MethodsTwelve commonly occurring weeds in western Canada, were chosen for this experiment. These species include weeds from a number of different families (Table 1) nd have a range of seed coat hardness. Preliminary StudyA preliminary study was carried out at the Olds College Composting Centre. be maintained within the optimum range to kill the seeds of the twelve selected species of weeds. Windrows of a typical feedlot manure mixed with beddingThe goal was to determine how long the compost windrow temperatures must

Weed Seed Viability in Composted Beef Cattle Feedlot Manure

“…Tompkins et al (1998) found that weed seed viability was zero for wild buckwheat, green foxtail, and stinkweed after 14 d of composting and zero for all 12 weed species in their study after 28 d. In contrast, wild buckwheat was one of the most resilient weeds in our studies. It showed viable seed after 42 d in 1999 (Table 3) and even after 70 d in 1997 (Table 2).…”

The biology of Canadian weeds. 138. Kochia scoparia (L.) Schrad.

“…Composting feedlot manure can eliminate kochia seed viability. After 2 wk of composting manure in a windrow, with core temperatures between 55 and 658C, all kochia seed was non-viable (Tompkins et al 1998). In another study, kochia seeds buried in compost were non-viable after 3 d at 508C (Wiese et al 1998).…”

The biology of Canadian weeds. 130. Amaranthus retroflexus L., A. powellii S. Watson and A. hybridus L.

“…Seeds of A. retroflexus survived digestion by 10 month-old lambs (Ozer 1982), rumen digestion by cattle (27-45% of the seeds survived) and ensiling followed by rumen digestion (1-6% of the seeds survived) (Blackshaw and Rode 1991). A small percentage of A. retroflexus seeds (3.5%) survived after two weeks of windrow composting at temperatures of 55-65°C (Tompkins et al 1998). Seed dispersal may also occur through the spreading of cow manure, composts or sewage sludge on farmland (Chytil 1986;Eberlein et al 1992;MtPleasant and Schlather 1994).…”

“…Composting manure in a windrow with a core temperature between 55 and 65°C reduced viability of seeds of A. retroflexus to 0% after 4 wk (Tompkins et al 1998). Redroot pigweed seeds preincubated for 1 d in pig slurry and dried for 3 min at 75°C lost viability (Bloemhard et al 1992).…”