Tips on Using the 4Rs for Nitrogen Applications in Citrus
Column • July 10, 2025
By: Mike Roberts
The Coalition for Urban Rural Environmental Stewardship (CURES) has created a series of videos for growers looking to up their game when it comes to nutrients; each video focuses on the 4Rs of nitrogen management—Right Rate, Right Time, Right Place, and Right Source—and how to use that information to guide nitrogen applications for a handful of different crops, including citrus. The citrus video shares key takeaways on nitrogen management for citrus with an aim of reducing the leaching of nutrients and saving money on inputs.
Takeaways on Nitrogen Applications
CURES is a group that focuses on educational efforts for agricultural and urban communities with the aim of creating and delivering science-based solutions and education to protect both people and the environment.
The video shares these takeaways on nitrogen applications for citrus growers:
- There are three forms of nitrogen in the soil: Soil organic matter that breaks down over time and releases nitrogen slowly; Ammonium, which is difficult for roots to take up due to its positive charge; and nitrate, which can be applied via fertilizers. Nitrate is easy for roots to take up due to its negative charge, but it also makes it easy for nitrogen to leach.
- Citrus trees will limit their uptake of nitrogen when they already have all the nitrogen they need at that moment, meaning excess nitrate in the soil will leach away.
- Applying nitrogen in smaller amounts over multiple applications as the trees need it—called spoon-feeding—is the best method for getting your citrus trees the nitrogen they need, limiting leaching, and saving growers money on inputs.
- Timing nitrogen applications with tree demand is the best way to match the available nitrogen in the soil with the tree’s nitrogen needs; mature citrus trees’ demand for nitrogen increases when shoot growth and fruit development begin. It peaks as the citrus fruits enlarge and coincides with vegetative growth. It starts to taper off with fruit maturity, and it is at the lowest at harvest.
- It’s not worth applying nitrogen before the new leaf flush because citrus tree roots are not yet taking up nitrogen.
- Leaf analysis is one of the best tools to guide citrus growers on their trees’ nitrogen needs; testing should occur after flower and fruit set as fruit are growing to ensure there is enough nitrogen as fruits mature.
- The right place to apply nitrogen is where the majority of a citrus tree’s important feeder roots are located, usually in the first two feet or so of soil where the tree is also taking up the majority of its water.
- It’s important to know when the form of fertilizer you are applying will have nitrogen available for the trees; warm, wet conditions increase the conversion of urea ammonium nitrate to nitrate, for example.
Your local UF/IFAS Citrus Extension agent and knowledgeable fertilizer distributor are great resources for helping you determine the Right Rate, Right Time, Right Place, and Right Source for nitrogen applications for your citrus grove!
Link to CURES Videos: