By John M. Chater and Davie Kadyampakeni
Soil fertility is a keystone to a productive citrus grove in Florida. In the era of huanglongbing (HLB), the need to fine-tune soil fertility takes on even more importance.
The sandy soils found in citrus-growing regions of the state are great for drainage to reduce flooding stress of citrus trees in many cases, but this soil type comes with drawbacks. One is low cation exchange capacity, which limits availability of nutrients to tree roots. Another drawback is that fertilizer applied during the growing season, especially in summer months, can be washed through the soil profile and out below the rootzone (or rhizosphere), where the roots meet the soil and take up nutrients.
In the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) citrus breeding program, many efforts have been made to keep important citrus germplasm and commercially available varieties productive in the grove. One of the key observations by researchers is that fertilizers, particularly controlled-release fertilizers (CRF), seem to help keep trees healthier during the rainy growing season, thus promoting canopy density and fruit set.
There are many different blends and products of CRF fertilizer, and some may be better for citrus growing in the HLB environment than others. CRF releases small amounts of fertilizer as the rain comes down, which allows for a steady stream of nutrients to be available.
Use polymer-coated micronutrients in the fertilizer product. Solely coating the macronutrients is likely not as helpful.
For optimal response, it is encouraged to apply CRFs of 6-, 9- or 12-month duration two times per year to ensure continuous year-round nutrient availability. When customizing fertilizer blends, growers need to pay attention to soil and leaf tissue testing. Consult UF/IFAS Extension agents or faculty for guidance.
John M. Chater is an assistant professor, and Davie Kadyampakeni is an associate professor, both at the UF/IFAS Citrus Research and Education Center in Lake Alfred.
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