Effect of Apple Rootstocks and Length and Type of Interstock on Leaf Nutrient Levels

The levels of N, P, K, Ca, Mg, Cu, Fe, Mn and Zn were determined in the leaves of young apple plants over a four-year period. The treatments were three root-stocks, MM 111, MM 106 and M 9; three interstocks, Red Delicious (cv Red Prince) (RD), MM 106 and M 9; and four interstock lengths, 2·5, 7·5, 12·5 and 18 cm. The level of Ca was lower in the leaves of plants with an MM 111 rootstock than in those on MM 106 or M 9. The level of K in the leaves was lower on plants with an M 9 than with an MM 106 or RD interstock. Only lengths of M 9 inter-stock differentially affected the nutrient level, and these effects were not consistent. Nutrient levels of leaves from rootstock and interstock treatments were similar over the four-year period. A small differential effect was shown only on the level of Ca. Rootstock treatments differentially affected the levels of N and Ca in the leaves over the four-year period, whereas the interstock treatments differentially affected the level of Cu over the same period. The effects of interstock lengths on leaf nutrient levels over the four years were few and inconsistent.