Competition of Setaria faberii with Corn and Soybeans

The treatments in this 3-year study consisted of 54, 12, 6, 3, 1, 1/2, and no foxtail plants per foot of crop row. Yield reductions for the heaviest stand of foxtail averaged 25% for corn and 28% for soybeans. For both corn and soybeans, the increase in foxtail dry matter was proportional to the decrease in the dry matter from the crop; the combined yield did not vary significantly. As stand of foxtail increased, there was a decrease in yields of grain, cobs, stalks or straw, diameter of cornstalks, ear weight, light intensity beneath the crop, soil temperatures under corn, and number of soybean pods. There was little or no significant effect on moisture content of grain, height of crop, shelling percentage of corn, oil or protein content of beans, weight of 100 beans or number of beans per pod. Increased corn lodging was associated with increasing foxtail stand in one of three years.