By Aaron Himrod
Good nursery growers are constantly monitoring their nutrition levels to produce well-nourished plants. While a grove owner cannot employ the same intensity of nutritional control as in an enclosed structure with consistent plant media, the principles apply in the field just as much in the nursery. A steady supply of comprehensive nutrition in the appropriate balance is needed for optimal growth.
Standard dry granular fertilizer can be used with the understanding that it must be applied lightly and frequently. During periods of extensive rainfall, it can be leached out of the root zone. Also, if applied in a concentrated manner, it is also easy to cause a salt burn to the roots that will stunt or kill the tree. Many times, when this happens, the tree shows symptoms and/or death a significant time after the injurious event occurred, leaving the grower wondering why.
Liquid fertilizer is another option and is applied in proportion to the irrigation system, making it vulnerable to waste if the root zone has not adequately colonized the entire irrigated area or if irrigation uniformity is poor. Drip emitters and focused microsprinklers are ideal candidates for this fertilization method if designed well.
Remember that not all nutrients are compatible in concentrated, liquid form. This means that it is impossible, for all practical purposes, to provide all the necessary nutrients in the needed concentration from the same tank/fertilizer blend. Multiple tanks and pumps or frequent rotation of manual fertilizer injections using blends that complement each other’s deficiencies are needed to provide the entire suite of nutrients if a grower wishes to commit exclusively to this method.
Controlled release fertilizer is another option. It significantly reduces, but does not eliminate, the chance of waste and injury to the tree. Each blend should have a timeline associated with that formulation printed on the bag. Choose a manufacturer/seller that you can trust and get an honest assessment of the true release curve characteristics in Florida conditions. Heat and moisture impact the release rates, and the timelines listed on some products are calibrated for very different environmental conditions than Florida and can cause the fertilizer to release prematurely, effectively concentrating the front end and starving the tree on the back. Like liquid, most products lack all the needed nutrients in the appropriate amounts.
Your irrigation water and soil bank are often forgotten suppliers of various nutrients. Have them tested so that you understand the contribution you are receiving from those sources. They can be significant.
To sum it all up, make a plan that fits your grove management scheme that provides a steady stream of all the needed nutrients in the right amounts to the root zone of your young plants.
Aaron Himrod is manager of Himrod Citrus Nursery in Florida. Hear his views on replanting trees in the face of HLB.