Brandon White with the University of Florida Institute of Food and Agricultural Sciences discussed the pros and cons of several types and methods of citrus fertilization at Citrus Nutrition Day on Oct. 26. The event was held at the Citrus Research and Education Center in Lake Alfred, Florida. White recently became the new commercial fruit crop agent for Florida’s Lake and Orange counties.
He addressed the soil-applied methods utilizing granular (dry) fertilizer, controlled-release fertilizer (CRF) and fertigation; as well as the foliar-applied method.
The advantages of traditional soil-applied granular fertilization are that it is inexpensive and the nutrients are readily available to the plant. Disadvantages are that it is subject to leaching and that multiple applications increase labor and costs.
CRF releases small amounts of fertilizer over time. Because the fertilizer is slowly released, it gives the tree a constant supply of nutrients. Another advantage is that it requires fewer applications than other fertilization methods. The CRF disadvantage is that it is expensive.
Fertigation is the application of liquid fertilizer though an irrigation system. Advantages are that it is relatively inexpensive, offers flexibility in application, and provides a constant nutrient supply in small doses. Disadvantages are that it is high maintenance, requiring a cleaning and flushing plan, and that it is not suitable for all nutrients.
Foliar-applied is the quickest fertilization method and it allows growers to assist trees during times of high demand or other hindering conditions such as wet, dry or cold weather. Disadvantages are that a foliar nutrition program must be coupled with a soil nutrition program and that it causes leaf burn when not applied at the correct time.
SOIL pH AND TESTING
In another segment of his presentation about strategies for improving nutrient uptake efficiency, White asked, “After ensuring crops have sufficient water, what is the next most important thing to ensure for crop health?” The answer was soil pH. White called soil pH the “principal factor for fertility and crop nutrition” and said it is recommended growers keep soil pH between 5.8 and 6.5.
He said soil testing is most valuable when done throughout the year and is evaluated for trends over multiple years. He added that soil and tissue testing are best done in tandem, and said tissue testing shows what nutrients actually make it into the plant.
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