California Citrus Newsletter

February 2024


Start your 2024 Season Off Right and Defend your Citrus against Puff and Crease

We are well into the month of February and most citrus growers have completed their foliar applications of lo-bi urea. As I have mentioned in previous newsletters, foliar applications of low-biuret urea in citrus is a safe and very common grower practice that can increase fruit set (demonstrated by Dr. Carol Lovett’s research). Adding other essential nutrients to your foliar nitrogen application can be effective in correcting deficiency symptoms as well as boosting overall tree health.

Many citrus growers this past season mentioned that their crop experienced quite a bit of puff and crease, a rind defect. Puff and crease cause misshapen fruit and the separation of the albedo (the white material under the outer peel) from the outer peel. The fruit affected will have an uneven and puffy appearance. This makes citrus fruit less desirable and even unmarketable as the quality is impaired. Puff and crease internal damage can occur based on plant physiological responses and nutrient deficiencies. Mild, warm fall/winter months and possibly late nitrogen applications can cause more prevalence of these issues. Leaf tissue analysis of nitrogen levels above 2.6% may contribute to this disorder if other elements are out of balance.

Balanced nutrition without deficiencies is key to reducing puff and crease in citrus. When deficiencies exist, tree and fruit production and quality can be limited. Puff and crease have been found in phosphate-deficient trees accompanied by very high nitrogen rates applied. Also, potassium deficiency can limit endocarp growth and fruit brix in addition to the tree health. Mitosis, or cell division, is dependent upon calcium and zinc availability. Without sufficient calcium fruit creasing in the rind can occur. Balanced nutrient levels can reduce senescence only so much due to climate conditions.

Nitrogen form also plays a significant role in citrus production. Nitrate is the preferred form of nitrogen since the citrus tree exhibits ammonium toxicity under stress conditions. Some great options would include YaraLiva® CN-9® or YaraLiva® CAN-17™. YaraLiva CN-9 has 93% nitrate N and YaraLiva CAN-17 has 68% nitrate N. The addition of soluble calcium by these sources is beneficial as well, as calcium is the third most needed nutrient by the citrus tree. UAN-32 is composed of 50% urea, 25% ammonium N and 25% nitrate N. After the urease reaction, 75% of the N is applied as the ammonium fraction. Applying UAN-32 to acid soil can be dangerous. When the soil pH drops below 5.5, bacterial functions will cease so nitrification will be extremely limited and much ammonium N can be available to a tree that exhibits ammonium toxicity when UAN-32 is applied. This was observed in a Yara citrus trial in Brazil.

If you would like to run UAN-32 as your first soil-applied N, consider adding calcium to the blend to make the use of UAN-32 more effective, and more efficient. UAN-32 + YaraLiva CN-9 (calcium nitrate) can create a unique blend called YaraLiva® UCAN®-23 that is then considered an Enhanced Efficiency Fertilizer by the Association of American Plant Food Control Officials (AAPFCO). The soluble calcium in a YaraLiva UCAN-23 blend does not allow the pH to be driven up and cause volatilization of the ammonia.

YaraLiva UCAN can provide several benefits:

  • Nitrate, ammoniacal, and urea nitrogen for a balanced approach to nitrogen fertility
  • Quick and prolonged plant-feeding
  • Soluble calcium for root and shoot growth
  • Less nitrogen loss to the atmosphere, meaning less environmental impact and more efficiency
  • Accepted as AAPFCO as an Enhanced Efficiency Fertilizer

YaraLiva UCAN-23 Guaranteed Analysis

Total Nitrogen (N) 23.0% Calcium (Ca) 4.0%
     Nitrate N (NO3) 8.0% Bulk density 11.45 lbs/gal
     Ammonium N (NH4) 5.0% pH 6.0-6.5
     Urea N 10.0%    
Derived from Hydrated Ammonium Calcium Nitrate Double Salt and UAN


Consider adding dependable and effective YaraLiva CN-9 to your citrus crop nutrition program this season. This nitrate form is not temperature dependent on release or availability as some other options such as urea forms. The money you save on a less expensive form may actually cost you more, in the long run, this season because of volatile losses. If you absolutely want to use UAN-32 in the early season, consider adding YaraLiva CN-9 to the blend to make it more efficient and effective!

Ammonium (NH4+) to nitrate (NO3-) via soil bacteria

Soil temperature (°F) Time for conversion (weeks)
40 6+
50 2+
75 1+


Effect of soil temperature on nitrate formation

soil temperature effect on nitrification


Refer to your most recent analytical soil-leaf tissue reports, and a Yara Agronomist is available to help you put together a more targeted and efficient citrus crop program.

YaraLiva CN-9 and YaraLiva TROPICOTE (dry spreadable calcium nitrate) provide immediately available nitrate nitrogen and water-soluble calcium.

  • Nitrate nitrogen increases plant growth by enhancing the uptake of other essential nutrients such as calcium, magnesium, and potassium
  • Water-soluble calcium promotes proper cell division for larger fruit and less chance of disorders such as creasing
  • Readily available calcium also promotes root health and root growth for efficient water and nutrient uptake and salinity management

Additional nutrition considerations for early vegetative and spring flush

citrus growth stages

Leffingwell® Nutra-Phos® CalZinc 0-24-0 and Leffingwell® Nutra-Spray ZM®  are fully formulated foliar-applied products providing great solutions for early vegetative and spring flush nutrition.

  • High analysis, pH neutral, wettable powder that provides the essential nutrient availability over several days-weeks, giving a cost-effective treatment foliar option.
  • Extremely fine particle size gives thorough coverage, efficient nutrient uptake, and enhanced sprayability.

citrus orchard in california


Contact your Yara representative to discuss crop nutrition options.

Vanessa Vicencio

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


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