Most growers are familiar with the four “R’s” of fertilizer. Using the right rate, the right placement, the right source and at the right time. Let’s expand a little on this if you’re using a controlled-release fertilizer (CRF) on young citrus trees.

When using a CRF make sure you understand the technology and how it works along with the actual product you decide to purchase. Many “controlled-release” fertilizers are not 100% controlled-release, some are as little as 30% controlled-release. This means a portion is quick release and subject to leaching, run off and volatilization. More importantly this type of blend has a higher phytotoxicity or burn potential, so be sure you understand what you’re getting. Let’s review the 4 “R’s” when using a CRF:

Right Rate: since a CRF is designed to last longer you’ll need to pay attention to the length of release. If the product is designed for 6 months, you need enough “food” in order to adequately supply the plant. Just because it’s controlled-release does not mean you can underfeed the plant. Cutting the rate might save you some money on the initial purchase but you’re doing this at the expense of the tree! You won’t get the results you’re looking for -- remember, your goal is to get the tree into production as soon as possible. CRF’s are more efficient and you should be able to reduce your overall rate, but be careful you don’t reduce the tree’s potential.

Right Placement: Since a CRF releases over a period of time it’s critical that you put the product out in a way that insures it’s picked up by the tree. If the material is 100% coated you can place it right up to the tree trunk without fear of burning the roots. In fact, Harrell’s has many blends which can be added directly to the planting hole without any phytotoxicity. Normally the product should be applied directly over the root zone. It’s a good idea to “kick” a little dirt on the material to ensure it’s not displaced by a heavy rain or any other activity in the grove.

Right Source: Make sure the CRF you’re purchasing is designed for your specific crop. In this case, citrus. Additionally make sure it’s release is accurate for your geography. Many CRF’s make statements that they last for 6 months but when you use them they don’t go the distance. Why? Some are designed for lower temperature climates and when exposed to the Florida climate they just don’t measure up. It’s a good idea to check the specifications to see at what temperature the longevity statement is based.

Right Time: Timing is important with CRF’s but not as much as with conventional or quick-release products. Since CRF’s release over a longer period of time you have much more flexibility with application dates. I would suggest you look into the longer release (1 year) CRF’s rather than the 6 month or less products since the longer release products give you more flexibility and mean less labor. Why would you want to make 2 applications when you could do the same thing with one? Remember the first “R” (rate), if you use a 1 year product you need to put enough to feed for the whole year.

Contact your local Harrell’s Specialty Ag rep for your specific needs.

1 year old citrus reset that has received its 2nd production year application of 17-6-12 (2 lbs.)