What are the nutrients that are most critical to citrus fruit color, weight and size? What about a citrus fruit’s juice content and color, or its acid and soluble solids content? Or what about peel thickness? What are the most important characteristics of a good citrus crop? And what are the best nutrients for citrus crops? We’ve collected helpful information to help you make informed decisions about your citrus crop nutrition plan. We’ve also updated this post in 2023 to give you the most up-to-date information.
The Best Nutrients for Citrus Crops
It’s about applying the right nutrients at the right time, says Bob Rouse, associate professor and citrus horticulturist at University of Florida IFAS. Citrus trees are most active and develop new growth the first six months of the year, so that would be the time to apply about 2/3 of nutrients applied to a crop.
“Rains always work against you,” Rouse says. “That’s another reason to get 2/3 of fertilizer out in the first half of the year. Florida’s rainy season doesn’t start until June or early July. The tree stores fertilizer nutrients really well before then.”
According to Rouse, there are four nutrients that most affect these key characteristics of citrus: nitrogen, phosphorus, potassium and magnesium.
To learn more about the best nutrients for citrus crops and the ideal amounts for each, take a look at the Nutrition Of Florida Citrus Trees provided by the University of Florida Extension.
#1: Nitrogen
Of course, the number one best nutrient for citrus is nitrogen, and the amount taken up by trees can positively or negatively affect citrus fruits. Nitrogen plays an important role for many plants, and this is also true for citrus fruit trees. There is a balance between under and over application that can make the difference between a successful citrus harvest and a disappointing one. So how does nitrogen affect citrus trees?
• Adding nitrogen increases fruit juice content.
• Increases soluble solids (sugars) and increases acid slightly. Growers need to balance the increases from the sugars and the slight increase in the acid, which affects the flavor of the fruit and can lead to an acidic-tasting juice.
• Increases the juice color. Increasing solids or sugars on per box basis is what growers are paid for. “[Increasing nitrogen] will increase the sugar, so that means growers get more money,” Rouse says. “There’s a relationship there between profit and use of nitrogen.”
• Too much nitrogen can make the fruit green, preventing it from coloring up, and also makes an undesirable thicker peel.
• Too much nitrogen will make fruit puffy inside with less juice, as well.
#2: Phosphorus
Phosphorus is another important nutrient for many different plant functions. Phosphorus applied during citrus production can work to counteract too much nitrogen, and a healthy balance between them is important.
• If you exceed the recommended ranges of phosphorus, it can negatively affect the acid content, pulling it down.
• Excess phosphorus can also increase the ratio of sugars to acid, since acid is decreasing during fruit maturity.
• Phosphorus has no effect on fruit size or weight, but will make fruit stay green if over applied, as nitrogen also does.
• Phosphorus can also help to keep peel thickness to a minimum.
#3: Potassium
Potassium does have quite an effect on the external part of the fruit. This is also an important nutrient for citrus trees, and can have a number of different affects.
• Potassium can increase your fruit size and weight.
• Over application of potassium can cause the fruit to stay green and not color up at the end of the season.
• Potassium can keep the peel thickness from being too thick.
• Potassium may increase acids, but it can also increase sugars.
#4: Magnesium
Magnesium is the last nutrient that is best for citrus crops. Chlorophyll is the driving force for making sugars in fruit. The magnesium is the center of the chlorophyll molecule, so plenty of magnesium means plenty of chlorophyll.
• In addition to increasing sugars, magnesium will also increase the ratio of the amount of sugars to the amount of acid and will result in a better tasting fruit or juice. That’s the main function of magnesium.
• Externally, magnesium can increase size and weight of fruit, because you’re increasing sugar content, which results in a heavier fruit.
• Magnesium can negatively affect the peel thickness, however.
Optimizing yields for citrus trees can be complicated, as there are many different factors to consider. If you think that a nutrient deficit could be slowing down the growth, development, or yields of your citrus trees, we can help. Contact us to learn more about custom fertilizer and nutrition plans for your citrus crop.
