EFFECTS OF NITROGEN FERTIGATION ON FRUIT YIELD AND QUALITY OF YOUNG 'FRENCH' PRUNE TREES

SummaryIn 1991, a 3.6 ha plot was established to determine the effects of urea fertigation via drip emitters on growth responses and yield of young `French' prune trees. Urea N (UN32) was applied annually beginning in 1992 and continuing through 1996 at 0 (control), 0.11, 0.23, and 0.45 kg actual N per tree as biweekly applications with one-tenth of the total amount per application from May until September. An additional annual treatment delivered 0.06 kg N per tree if July analysis of leaf N showed 2.3% or lower total N. Fruit yield, number of fruit per kilogram, drying ratio (fresh fruit mass per dry fruit mass), tree growth (trunk cross-sectional area and mass of pruned shoots), leaf N concentration, and soil nitrate content were assessed as a function of treatment. Dry yields per tree were increased by N treatments compared with the control in 1994 and 1996 and when averaged over three years. Fruit size and drying ratio were not affected by N treatments during any year. Where no N was applied, there w...