Minimal Nutrient Flux in Leaves of 'Fuji' Apple Trees on Two Rootstocks

Abstract

The goal of this study was to monitor the seasonal trends of different nutrients in 'Fuji' apple leaves on M.9 337 and M.7 EMLA rootstocks for two years, and to determine 'Fuji's' period of minimal flux using regression analyses. The effects of rootstock on 'Fuji' seasonal trends and the interactions among leaf and fruit minerals were examined. The period of minimum flux for nitrogen in 'Fuji' apple leaves occurred at 40-140 days after full bloom (DAFB). Nitrogen (% d.wt), K (% d.wt.) and Zn (p.p.m.) concentrations in leaves from trees on both rootstocks decreased during both growing seasons. Calcium (% d.wt.) and Mn (p.p.m.) concentrations increased in leaves from trees on both rootstocks throughout both years. Magnesium, Fe and Cu trends were inconsistent from year to year. However, seasonal fluctuations in leaves from trees on both rootstocks were always similar regardless of differences between years. Trees on M.7 EMLA had lower leaf N, but higher leaf K and Ca, than those on M.9 337 through out both growing seasons. Rootstock effect on K levels was significant during both years. Calcium con centrations were not affected by rootstock in 1995, when the crop load was very light, but in the heavy cropping year 1996, the effect was significant. The period of minimal flux of N in 'Fuji' leaves from mid-June until September is little affected by crop or rootstock. The stable sampling period for foliar analysis of 'Fuji' apple extends from 40-140 DAFB, providing growers more time to respond to ana lytical results than the August-only sampling period appropriate for some other cultivars.