Competition of Common Milkweed with Sorghum
1973
Evetts, L. L. | Burnside, O. C.
Common milkweed (Asclepias syriaca L.) is a deep-rooted perennial weed that has increased in occurrence in recent years and has caused much concern among landowners. Because it occurs frequently in dryland sorghum [Sorghum bicolor (L.) Moench], a 3-year competition study using paired plots was conducted to determine the degree of yield loss caused by common milkweed. Sorghum yield and number of heads per hectare were significantly reduced by common milkweed competition each of the 3 years. Common milkweed reduced average yield by 21% and number of sorghum heads per hectare by 14%. Even low populations (less than 12,000 plants/ha) of common milkweed resulted in severe yield losses. Grain weight per head was significantly reduced by common milkweed competition in 1970 and 1972 but not in 1971. Competition had no effect on sorghum 500- seed weight in 1971 or 1972. Percentage protein (Kjeldahl method) of sorghum grain was significantly increased by competition in 1972 but not in 1971.
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