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Interference of common sunflower, tall waterhemp and velvetleaf in soybeans and growth and herbicide response of selected pigweed species
Abstract
Soybean yield reductions from sunflower and velvetleaf on a per plant basis were over twice as great in 1986 as in 1987, but were similar on a total weight basis. Tall waterhemp caused greater yield reductions on a total weight basis in 1987 than in 1986, but similar reductions on a plant basis each year. Soybean yield reductions from sunflower interference were 27 percent at 2 sunflowers per 11.3m row in 1986 and 17 percent at 4 per row in 1987. Yield reductions from 6 velvetleaf per row were 22 and 7 percent and from 6 tall waterhemp 15 and 12 percent in 1986 and 1987 respectively. To economically justify postemergence control 0.4 and 1.2 sunflower, 0.5 and 7.8 velvetleaf, and 1.1 and 1.2 tall waterhemp were needed per 10m row 1986 and 1987 respectively. In growth chamber studies fresh weight of grain amaranth and giant pigweed were highest and prostrate pigweed lowest at 30/24C, 24/18C and 18/12C day/night temperature regimes. Giant pigweed emerged and grew most rapidly. Giant, grain and Palmer were least and tall waterhemp and redroot most susceptible to preemergence herbicides. Metolachlor applied preemergence at 0.84 kg/ha resulted in 52 and 74 percent grain amaranth and prostrate pigweed growth reduction compared to 94 to 100 percent for the others. Least susceptible to postemergence herbicides were spiny, Palmer and giant pigweed with prostrate, tumble, and redroot pigweed most susceptible. Bentazon applied postemergence resulted in 4, 39 and 36 percent control of spiny, Palmer and giant pigweed, compared to 74, 59 and 52 percent for redroot, tumble and prostrate pigweeds. 14C bentazon absorption did not always correspond to growth reduction of pigweeds. Least 14C was absorbed by prostrate although growth reduction was high. Palmer, giant and smooth also absorbed little 14C. Tumble, redroot and spiny amaranth absorbed a high amount of 14C bentazon with a corresponding high growth reduction of tumble and redroot pigweeds, but little growth reduction of spiny amaranth.
Subject Area
Agronomy
Recommended Citation
Hayden, Thomas Allen, "Interference of common sunflower, tall waterhemp and velvetleaf in soybeans and growth and herbicide response of selected pigweed species" (1988). ETD collection for University of Nebraska-Lincoln. AAI8904489.
https://digitalcommons.unl.edu/dissertations/AAI8904489