Weed Suppression Utilizing Hairy Vetch (Vicia villosa Roth) Living Mulch in Forage Corn (Zea mays L.) Cultivation

Abstract

We conducted field experiments during the period 2007-2010 to explore methods of controlling growth of hairy vetch (HV) living mulch in stands of forage corn produced without herbicides in cold region of Japan. Corn seed was planted without tilling into HV sod established in the previous year. The HV sods were then mown before corn seed germination. Mown dead sods and regrown new shoots of HV effectively depressed weeds without herbicides. However, delaying the date of HV sowing or advancing the date of corn sowing allowed excessive regrowth of HV, with consequently reduced corn yields. Optimum sowing times for weed suppression and higher corn yield were mid-September for HV and mid-May for corn. Corn yields from this combination of sowing times matched those from conventional tillage with herbicide application. We demonstrated further that vertical disc harrow cutting of HV sod before corn planting suppressed regrowth of HV more effectively than mowing, if the harrow gang angle adjusted to prevent overturning of sod. This disc harrow procedure reduced losses in corn yield caused by delaying the date of HV sowing.