Citrus breeder Jude Grosser recently shared tips on tree nutrition and discussed some scion/rootstock combinations that should work well for trees producing juice oranges.
Grosser became very interested in citrus nutrition several years ago in an effort to keep his newly bred trees healthy in the face of HLB. The University of Florida Institute of Food and Agricultural Sciences professor credits Florida citrus grower Maury Boyd with teaching him about nutrition. Boyd focused on nutrition as an aid to keeping trees healthy soon after HLB became widespread in the state in 2005.
Grosser said the following nutrition observations and tips came from his own experience:
- HLB causes severe deficiencies of secondary nutrients and micronutrients — not nitrogen, phosphorus and potassium (NPK). The deficiencies are twice as great in the roots as in the leaves. This problem must be corrected for restoration of proper vascular system function.
- HLB-affected trees need a constant enhanced supply of secondary/micronutrients year-round. Pay attention to nutrient ratios. A constant supply of micronutrients can stop fruit drop, improve fruit quality to pre-HLB levels and improve yields. Use of controlled-release fertilizer (CRF) is a good way to address this problem, but growers should pay close attention to the label, since many expensive CRF products only have NPK polycoated, and not the minor nutrients. The secondary nutrients and micronutrients must be polycoated, Grosser emphasized.
- High-quality CRF products are expensive, so Grosser and others are testing a soluble dry program on producing trees with four applications annually. The second and fourth applications contain enhanced CRF secondary nutrients and micronutrients.
Grosser’s favorite orange scions for processing are Valquarius, Valencia B9-65 and OLL-4, 8 and 20. He thinks they can be viable with a good nutrition program on these rootstocks: UFR-1, UFR-2, UFR-4, UFR-5, UFR-6, UFR-7-12, UFR-15, UFR-17 and X639.
Grosser suggested that growers seek advice on which rootstocks to use in various conditions.
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