MECHANICAL VERSUS HERBICIDAL STRATEGIES FOR KILLING A HAIRY VETCH COVER CROP AND CONTROLLING WEEDS IN MINIMUM-TILLAGE CORN PRODUCTION

Authors: Teasdale, John; ROSECRANCE, RICHARD - CHICO STATE UNIV

Submitted to: American Journal of Alternative Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2002
Publication Date: 3/1/2003
Citation: Teasdale, J.R., Rosecrance, R.C. 2003. Mechanical versus herbicidal strategies for killing a hairy vetch cover crop and controlling weeds in minimum-tillage corn production. American Journal of Alternative Agriculture. 18(2):95-102.

Interpretive Summary: Hairy vetch is a popular cover crop that is grown during the winter and spring months before planting corn in the mid-Atlantic states. Residue from a hairy vetch cover crop can provide many desirable benefits both to the succeeding corn crop and to the environment. Current systems for minimum-tillage corn production with a cover crop require herbicides to kill the cover crop before planting and to control weeds emerging after planting. However, there is a need to develop systems that take advantage of the benefits derived from minimum-tillage production with cover crops but that reduce or eliminate use of herbicide inputs. Research was conducted to determine whether production systems that employ mechanical approaches to killing cover crops and controlling weeds could perform as well as those employing herbicides for minimum-tillage corn production in a hairy vetch cover crop. Although weed control was not as efficient in the mechanical versus herbicide systems, weed populations in the mechanical systems were maintained below threshold levels in 2 of 4 experiments and the vetch cover crop was adequately killed if performed at the flowering stage. With further research and equipment development, reliable minimum tillage systems could be developed for organic farmers or for situations where environmental resources are especially sensitive to herbicide losses. Organic field crop producers, in particular, would benefit from such a system since they have identified weed management as well as tillage systems and soil conservation among their top ten research priorities.

Technical Abstract: There is a need to develop minimum-tillage production systems that reduce or eliminate herbicide inputs. This research was conducted to evaluate an integrated strategy for minimum-tillage corn production in a hairy vetch cover crop with mechanical versus herbicidal methods for preplant cover crop kill and for postemergence control of emerged weeds. Preplant treatments included 2,4-D plus residual herbicides, 2,4-D alone, flail mower, corn stalk chopper, light disk, and heavy disk. The preplant herbicide treatments were followed by a postemergence treatment of dicamba, whereas, the preplant mechanical treatments were followed by postemergence cultivation as needed for weed control. The mechanical treatments that kept residue on the soil surface (mower, stalk chopper, and light disk) killed hairy vetch when it was flowering but not when it was vegetative. The herbicide treatment with preplant 2,4-D alone followed by dicamba postemergence controlled annual broadleaf weeds (the dominant species in these experiments) similarly to treatment with 2,4-D plus residual herbicides suggesting that residual herbicides may be eliminated in cover crop-based no-tillage systems. The preplant mechanical treatments followed by cultivation did not control annual broadleaf weeds as well as herbicide treatments but did maintain final populations below threshold levels in two of four experiments. The chopper and light disk left high levels of vetch residue on the soil surface and reduced initial weed populations compared to the heavy disk which incorporated most residue. However, the efficiency of broadleaf population reduction by the cultivation of untilled soil following the chopper or light disk (38 to 69%) was lower than cultivation of tilled soil following the heavy disk (87 to 95%). Pigweed survival within row following cultivation was 30, 50, and 92% for plants 2.5, 5, and 15 cm high, respectively, indicating the need to cultivate when pigweed is small to achieve adequate control.