ROOT DISTRIBUTION PATTERNS OF 9 APPLE ROOTSTOCKS IN 2 CONTRASTING SOIL TYPES

Root distribution of Starkspur Supreme Delicious' on nine apple (Malus domestica Borkh.) rootstocks grown in two different soil types in the 1980 NC-140 Uniform Apple Regional Rootstock Trial (Michigan and Ohio sites) was determined using the trench profile method. Based on the number of roots counted per tree, rootstocks could be separated into five groups for the Marlette soil from most to least: MAC.24 > OAR1 > M.26EMLA = M.9EMLA > M.7EMLA = 0.3 = M.9 = MAC.9 > M.27EMLA. For the Canfield soil, rootstocks were ranked for number of roots counted from most to least as follows: MAC.24 > OAR1 = MAC.9 = M.7EMLA > M.26EMLA = 0.3 = M.9EMLA = M.9. Root distribution pattern by depth was affected by soil type with roots fairly well distributed throughout the Marlette soil but restricted primarily above the fragipan in the Canfield soil. Two rootstocks performed differently from others in adapting to soil conditions at the different sites. MAC.9 had the second lowest number of total roots/dm(2) in the Marlette soil yet the second most in the Canfield soil, while the opposite was found for M.9EMLA. Regression analysis demonstrated positive correlations between number of roots counted and vigor and yield of the scion.