Reducing Weed Seed Viability


Dr. Robert Blackshaw and Dr. Lyle Road, with Agriculture and Agri-Food Canada, Lethbridge conducted research in 1991 to evaluate weed seed germination by ensiling the crop or feeding it to cattle. They tested twelve common weeds found in Western Canada: wild oats, green foxtail, downy brome, foxtail barley, barnyard grass, redroot pigweed, lamb’s quarters, wild buckwheat, kochia, field pennycress, flixweed, and round-leaf mallow.


Seeds were either placed in a silage pit for eight weeks, digested in the rumen for 24 hours, or a combination of the two treatments. Grassy species were more adversely affected than the broadleaf species. Small seeds with a hard seed coat tended to have higher survivability than the larger grassy seeds.


Green foxtail, downy brome, foxtail barley, and barnyard grass had zero germination and zero viable seeds when either ensiled or fed to cattle.


Viable seeds after ensiling and feeding to cattle was as follows: kochia10%, flixweed 5%, redroot pigweed 4%, green foxtail 17%, common lambs’ quarters 2%, wild buckwheat 19%, field pennycress 10%, and round leaf mallow 17%.


Results for reducing wild oat germination was variable. One year seeds fed to cattle had almost no reduction in the germination rate. In the second year of the trial, no wild oats germinated after being consumed by cattle. To prevent future wild oat problems, it is recommended that the crop be ensiled first and then fed to cattle to minimize seed viability and germination.


It was noted that the longer that weed seeds remain in the rumen, the viability decreased. For example, it required 8 hours for wild oats and downy brome to have reduced viability. Field pennycress required 12 hours. The smaller hard seeds had higher germination and viability compared to the larger grassy seeds.


This research was reported in the Journal of Weed Science, 1991. Volume 39, pages 104 – 108. “Effect of Ensiling and Rumen Digestion by Cattle on Weed Seed Viability”.


Contact Barry at 403-741-6032 or bjyaremcio@gmail.com for additional information.