and Moody, 1976). Also, when legumes are used as a living mulch, they can supply N to the main crop (Scott Previous research has shown that with adequate suppression, kura et al., 1987). clover (Trifolium ambiguum M. Bieb.) can be managed as a living mulch in corn (Zea mays L.); however, significant yield loss was Corn production in living mulch and interseeded sysobserved in some environments. This study evaluated two herbicide-tems typically results in yield loss in the North-Central resistant corn hybrids at three levels of kura clover living mulch USA from competition for moisture and N (Kurtz et suppression over multiple environments. In 1999 and 2000 near Arlingal., 1952; Pendleton et al., 1957). Fisher and Burrill ton and in 2000 near Lancaster, WI, glyphosate [N-(phosphonometh-(1993) and Zemenchik et al. (2000) also note that cool yl)glycine]-resistant corn (Roundup Ready corn, RRC) and glufosispring temperatures could reduce corn yields because nate [2-amino-4-(hydroxymethylphosphinyl) butanoic acid]-resistant of delayed planting or by giving a cool-season clover a corn (Liberty Link corn, LLC) hybrids were planted where kura clover competitive advantage over corn, a warm-season grass. had been (i) killed for monocrop corn, (ii) strongly suppressed with The key to the successful use of living mulches for glyphosate and dicamba (3,6-dichloro-2-methoxybenzoic acid), or (iii) corn production is controlling competition from the lightly suppressed with only glyphosate. Suppressed kura clover also had a 25-cm clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) plus mulch crop. However, if the mulch suppression is excesdicamba-killed band into which corn was planted. Subsequent post-sive, it will not recover. Zemenchik et al. (2000) showed emergence applications of glyphosate or glufosinate herbicide were that corn could be grown in a kura clover living mulch made for each hybrid. Corn whole-plant yield ranged from 17.3 to when adequately suppressed by herbicide, without re-19.9 Mg ha Ϫ1 , and grain yield ranged from 10.8 to 12.3 Mg ha Ϫ1 .duced corn whole-plant or grain yields. In this system, Yield of whole-plant and grain across both corn hybrids did not differ kura clover will recover to full production within 12 mo between monocrop corn and corn in strongly suppressed kura clover. of corn harvest. However, corn performance in the living Whole-plant yield of monocrop corn was 8 to 11% greater and grain

Annual ryegrass has been proposed as a cover crop in the corn–soybean cropping systems of the U.S. Midwest because of its low seed cost, rapid establishment, contribution to soil quality, weed suppressive abilities, and susceptibility to common broad-spectrum herbicides. However, cover crops can reduce the subsequent main crop yield by creating unfavorable germination and emergence conditions, harboring pests, and if not controlled, competing with the main crop. This study, conducted in Illinois, Oregon, and Tennessee, investigated the efficacy of glyphosate for annual ryegrass winter cover crop removal. Glyphosate at 415, 830, and 1,660 g ae/ha was applied to annual ryegrass at late tiller, second node, boot, and early flowering stages. Annual ryegrass control was consistently maximized with the highest glyphosate rate applied at the boot or early flower stage. Annual ryegrass biomass was generally the lowest with the highest rate of glyphosate applied at the earlier stages. Overall, no single application timing at any glyphosate rate provided complete control or biomass reduction of the annual ryegrass cover crop. A sequential herbicide program or a glyphosate plus a graminicide tank-mix probably will be needed for adequate annual ryegrass stand removal.

Previous research has shown that with adequate suppression, kura clover (Trifolium ambiguum M. Bieb.) can be managed as a living mulch in corn (Zea mays L.); however, significant yield loss was observed in some environments. This study evaluated two herbicide‐resistant corn hybrids at three levels of kura clover living mulch suppression over multiple environments. In 1999 and 2000 near Arlington and in 2000 near Lancaster, WI, glyphosate [N‐(phosphonomethyl)glycine]‐resistant corn (Roundup Ready corn, RRC) and glufosinate [2‐amino‐4‐(hydroxymethylphosphinyl) butanoic acid]‐resistant corn (Liberty Link corn, LLC) hybrids were planted where kura clover had been (i) killed for monocrop corn, (ii) strongly suppressed with glyphosate and dicamba (3,6‐dichloro‐2‐methoxybenzoic acid), or (iii) lightly suppressed with only glyphosate. Suppressed kura clover also had a 25‐cm clopyralid (3,6‐dichloro‐2‐pyridinecarboxylic acid) plus dicamba‐killed band into which corn was planted. Subsequent postemergence applications of glyphosate or glufosinate herbicide were made for each hybrid. Corn whole‐plant yield ranged from 17.3 to 19.9 Mg ha−1, and grain yield ranged from 10.8 to 12.3 Mg ha−1. Yield of whole‐plant and grain across both corn hybrids did not differ between monocrop corn and corn in strongly suppressed kura clover. Whole‐plant yield of monocrop corn was 8 to 11% greater and grain yield 8 to 9% greater than in lightly suppressed kura clover, respectively. Both hybrids had similar corn whole‐plant yield, but LLC grain yield was lower than that of RRC. Kura clover recovery in the season following corn production was similar among living mulch suppression treatments by mid‐July. Herbicide‐resistant corn technology allowed for consistent kura clover living mulch management with little or no whole‐plant or grain yield loss.