Effect of five weed control methods on growth and fruiting of ‘McIntosh’/M.7 apple trees

The growth and fruiting of 10-year-old ‘McIntosh’/M.7 apple (Malus domestica Borkh.) trees were compared under the following weed management systems: untreated control; in-row herbicide spray (paraquat + oryzalin); in-row rotary tilling applied in May, June and July; in-row rotary tilling plus oryzalin; in-row rotary tilling plus oats sown in August. All weed control methods increased tree growth compared to the untreated control over three years. In 1989 and 1990, rotary tilling alone provided less weed control compared to the herbicide treatment, while in July 1991, the reverse was true. In-row rotary tilling with herbicide and with oats resulted in weed control comparable to or better than the herbicide treatment except for the in-row rotary tilled plus oats treatment in 1990. All weed control methods resulted in lower weed density ratings compared to the control. Yield and fruit size were increased by all weed control methods except the rotary tilled plus oats treatment. In-row rotary tilling plus oats produced yield and fruit size equiva-lent to the control. Differences in leaf and fruit mineral nutrient concentrations were significant in some years. All weed control methods reduced soil K concentrations. There were no differences among treatments in fruit color, set, maturity, and percent soluble solids.