After a season of many challenges, citrus growers are happy to be harvesting… so let’s talk citrus crop nutrition

November 2023

It’s been a stressful year for many citrus growers. The rain earlier in the season caused many delays. Growers were unable to get into their fields to make critical fertilizer applications on time and the extended cool weather pushed crop maturity back at least a couple of weeks. The earlier weather conditions also affected bloom, causing issues and delays with important pesticide applications. Petal fall could not be declared as usual because of the prolonged and uneven bloom. The environmental weather conditions during bloom, cell division and cell expansion have a great role in quality fruit which is beyond our control. Our job is to anticipate and react with these conditions with essential nutrient elements to best meet crop demand. Supplying citrus trees with the right amount of nutrition is critical to prepare the tree for getting optimum quality fruit, hence the 4 R’s.

The goal of balanced nutrition is one of the most important factors that affect quality, set, size and yield, and storage potential of citrus fruit. A solid citrus crop fertilizer program that provides all essential nutrients when the crop demands them is critical. If the 2024 season turns out to be another rainy one, then it is very important that we have a backup plan for that. Thoughtful planning ahead is important, although the weather conditions can most definitely change overnight. Now is the time to have conversations with your CCA or PCA about what your citrus crop nutrition program will look like for the following season. A great place to start is by reviewing your current season’s nutrition program along with the most recent soil and tissue analysis. Did the current program meet the nutrient needs of the crop? Does it need to be adjusted? These are some good questions to start with when putting together your crop nutrition program for the following season.

Yearly Reminder: Winter Pre-bloom Fertilizer Applications

Winter pre-bloom fertilizer applications begin mid-December and continue through mid-February. According to Dr. Carol Lovatt’s research, this is the best time to apply foliar nitrogen to citrus. Foliar applications of lo-bi urea made during this time have been shown to increase fruit set and ultimately yield. Based on Lovatt’s research, just 0.35 lbs N/tree has been shown to increase yield (set and size) in mature navel orange trees.

A combination of lo-bi urea and other essential nutrients applied via foliar can be more effective than just applying a single nutrient. According to the ‘Law of the Minimum”, elements in least supply dictate success rather than those in greatest supply. Micronutrients such as zinc, manganese, and iron are commonly deficient in citrus. Taking advantage of this opportunity to apply nutrients is a great way to get ahead and stay ahead of any deficiencies that might be present but also to boost tree metabolism before flowering. It is recommended to keep your nutrient levels towards the higher range throughout the season to ensure that the trees will not run out when the nutrients are needed most. Getting the trees off to a strong start with lo-bi urea and a balanced foliar product is a key strategy.

Manganese supports photosynthesis, enzyme activation, and plant protein metabolism. Common symptoms are mottled yellow leaves. Severe deficiencies cause reductions in crop growth and yields. Manganese often occurs in combination with zinc and iron deficiency on calcareous soils.

Copper acts as a catalyst in photosynthesis and respiration. It affects protein production and pollen viability. Deficiencies in citrus cause dark green enlarged leaves. Twigs die back and gumming may occur under new bark or on fruit. Decreased yields due to poor flowering. Tissue analysis is the only way to determine status.

Iron acts as a catalyst in oxidation/reduction reactions and is involved in respiration and photosynthesis. Deficiencies in citrus cause chlorotic leaves with veins remaining green. Severe deficiencies lead to the entire leaf turning yellowish-white. Iron deficiency reduces fruit set and yield and can also lead to small fruit.

Zinc is another catalyst element in many of the enzyme and hormone systems used for protein synthesis and carbohydrate metabolism. Deficiencies in citrus cause small leaf and shoot size, and then chlorotic blotches of yellow between green veins (mottle leaf). Low zinc levels can reduce fruit number and size, resulting in decreased yields. All of these nutrients interact together and relate to how well your NPK, Mg, and Ca program will function.

Don't forget about calcium:

Tree health vigor based on calcium in your fertilizer program

citrus tree health vigor with and without calcium


Enhanced Formulation: YaraTera NITRAKAL MAX

Guaranteed Analysis  
Total Nitrogen (N) 10.0%
     Nitrate N (NO3) 9.5%
     Ammoniacal N (NH4) 0.5%
Soluble Potash (K2O) 7.0%
Calcium (Ca) 9.5%

YaraTera Nitrakal Max:

  • Provides a strong, balanced formulation of nitrogen, potassium and calcium that are immediately available for uptake
  • Nitrogen and potassium are important to achieving high marketable yields, uniformity of ripening, and proper brix in citrus fruit
  • Calcium is vital for improving citrus tree and fruit quality, health, growth, and firmness, while also improving soil and root quality


Vanessa Vicencio

Sales Agronomist at Yara North America - South Central Valley, California

Read the latest California Citrus Newsletter


Vanessa Vicencio
Vanessa Vicencio
Sales Agronomist

South Central Valley, California