MINIMAL NUTRIENT FLUX IN LEAVES OF FUJI APPLE-TREES ON 2 ROOTSTOCKS

The goal of this study was to monitor the seasonal trends of different nutrients in 'Fuji' apple leaves on M.9337 and M.7 EMLA rootstocks fo r two years, and to determine 'Fuji's' period of minimal flux using re gression 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.) con concentrations in leaves from trees on both rootst ocks decreased during both growing seasons. Calcium (% d.wt.) and Mn ( p.p.m.) concentrations increased in leaves from trees on both rootstoc ks throughout both years. Magnesium, Fe and Cu trends were inconsisten t from year to year. However, seasonal fluctuations in leaves from tre es on both rootstocks were always similar regardless of differences be tween years. Trees on M.7 EMLA had lower leaf N, but higher leaf K and Ca, than those on M.9337 throughout both growing seasons. Rootstock e ffect on K levels was significant during both years. Calcium concentra tions were not affected by rootstock in 1995, when the crop load was v ery light, but in the heavy cropping year 1996, the effect was signifi cant. The period of minimal flux of N in 'Fuji' leaves from mid-June u ntil September is little affected by crop or rootstock. The stable sam pling period for foliar analysis of 'Fuji' apple extends from 40-140 D AFB, providing growers more time to respond to analytical results than the August-only sampling period appropriate for some other cultivars.