Abstract
Products (Unity or Nitamin 30L at 120 or 150 lbs N/acre) that have some potential to slowly release N were compared as ground applied N sources for 4 years, from 6th to 10th year of ‘Hamlin’ orange and ‘Flame’ grapefruit trees. There were no significant yield differences using various N source fertilizer materials even though two of the treatments received products applied at lower rates. Overall yields were lower than expected, however, because the three hurricanes in 2004 passed over the planting and removed significant amounts of leaves and fruit in the first year. Subsequently, the trees never recovered to potential yield levels during this 4-year experiment. Pounds solids per box were higher in only one year for the SGF treatment, but soluble solids to acidity ratio was usually lower for this treatment due to higher acidity. Leached nitrates in the tree row where the fertilizers were applied were occasionally high after heavy rains but the fertilizer treatments did not greatly alter the average amount leached. A second test of foliar applied Nitamin 30L as a substitute for 60 lbs N/acre of the normal 180 lbs N/acre, did increase the yield of ‘Rhode Red Valencia’ trees in Lake Placid, FL. Juice quality and leaf N were not affected in the foliar test.
