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Abstract
One of the authors (Skroch) has been asking himself since the early years of a long-term study initiated in 1966 (77) “What is a weed to a tree?” Apple trees in the mowed grass check plots grew less than in plots with woody vines. In another test comparing mowed sod, contact herbicide, and residual plus contact herbicide, trees having an herbicide program yielded 400 bushels/acre more fruit in the 5th year than those without. Apples in another orchard were of higher grade in plots with over 50% trailing blackberry (Rubus sp.) and poison ivy (Rhus radicans L.) ground covers than those from an area with a mowed-lawn appearance. The practice of frequent mowing, which increased grass covers in the 1960s, may have been a factor in the small fruit problem of the 1970s.
Abstract
Two-year-old ‘Smoothee Golden Delicious’ apples (Malus domestica Borkh.) on seedling rootstock were planted in Spring 1981. Twelve different ground cover systems were then established. After one growing season, trees in mulch, bare ground, red sorrel (Rumex acetosella L.), and nimblewill (Mulenbergia schreberii J. F. Gmel.) treatments had greater shoot length than trees in legume, tall broadleaf, Kentucky bluegrass (Poa pratensis L.), orchardgrass (Dactylis glomerata L.), and ‘KY31’ tall fescue (Festuca arundinacea L.) treatments. In the 4th year, the trunk diameter of trees in straw mulch plots were greater than all other treatments. Tree growth in bare ground and cultivation treatments was not different over the 4 years and was as great or greater than in treatments with living ground covers. Trees in tall broadleaf, Kentucky bluegrass, orchardgrass, and tall fescue treatments were smaller than in all other treatments. Nimblewill, a native species to North Carolina mountains, has potential for replacing Kentucky bluegrass, orchardgrass, and tall fescue in orchard soil management systems.
Abstract
Two-year-old ‘Smoothee Golden Delicious’ apples (Malus domestica Borkh.) on seedling rootstock were planted into cultivated soil in Spring 1981, and 12 ground cover systems were then established. Apple leaves, twigs from pruning cuts, soil samples, and ground cover clippings were analyzed for nutrient content in 1983 and 1984. Leaf N content had the highest positive correlation with tree growth. Leaf P and K contents were negatively correlated with leaf N and tree growth. Twig N, P, K, Mg, Ca, and Zn contents were positively correlated with leaf N content and tree growth. Soil nitrate content was positively correlated with tree growth and leaf N content. Results implicate N competition as a major factor of interaction between apple trees and grass and broadleaf ground covers.