California Citrus Newsletter

May 2025

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Why Foliar Nutrition Early in the Season is Critical for Citrus

 

citrus pre-bloom stage

In California, we are just getting past the growth stage of “spring flush” which is also known as the “pre-bloom” timing. There are a lot of citrus growers that are still trying to catch up and finish their pre-bloom sprays, all while, counties are declaring petal fall. Pre-bloom, flowering and fruit set is the most important citrus timing when it comes to nutrition. The reason for this is because spring flush occurs alongside flowering and early fruit development. During this time, there is a HUGE demand for nutrients, as shown by the nutrient demand chart below; but a very short window of when they can be applied to get maximum uptake by citrus trees.

citrus nutrient demand chart

Foliar fertilizer applications are key during this time as citrus trees are very responsive to nutrients applied via foliar. Soil fertilizer applications have already started for the season and the current timing requires both soil and foliar nutrition to support bloom and fruit set. Nutrients to keep top of mind are N, K and Ca, as well as the micronutrients Zn and Mn.
  • Nitrogen is critical to continue supporting growth.
  • Citrus loves potassium. Potassium is needed in larger amounts than even nitrogen. This nutrient plays a role in enzyme activation, cell division, and photosynthesis. A deficiency in potassium leads to smaller leaf size, reduced vigor and overall tree health.
  • Calcium is needed for strong cell walls and is required throughout the growing season. Deficiencies cause poor fruit quality.
  • The micronutrients zinc and manganese play a role in chlorophyll formation, nitrogen metabolism and photosynthesis insufficiencies which can cause reduced leaf growth and reduced fruit quality.

Yara's Solutions Providing Critical Nutrients to Citrus

YaraTera® NITRAKAL™ MAX1 features a balanced, maximally concentrated blend of nitrogen, potassium and calcium; giving fruit trees critical nutrients that are immediately available for uptake.

YaraTera NITRAKAL MAX1
9% N (6.8% nitrate N, 2.2% ammoniacal N), 7% K, 3.5% Ca

Leffingwell Nutra Spray ZM is a cost-effective foliar option suppling Zinc, calcium and manganese.

Nutra Spray ZM
10% Ca, 18.5% Zn, 7% Mn    
 

The goal of balanced nutrition, N, P, K, Ca, Mg, and micros 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. Choosing the right form of a nutrient and applying at the right time is also very important. According to GreenCast, our average soil temperatures in the Central Valley do not reach 75ºF - 80ºF until about May. Most agricultural crops take up nitrogen as nitrate and most ammonium must be converted to nitrate before it can be utilized by the trees. Ammonium conversion to nitrate is microbe and temperature dependent, so choosing a nitrogen that is available (nitrate) at the right time immediately is key to an effective citrus crop program.

Always Refer Back to Those Most Recent Soil and Tissue Analyses

Tissue analyses should have been pulled last fall (September – October) to see where those nutrient levels were at that time. This gives us enough information to put together an efficient citrus crop program now, that we can adjust throughout the season.

A combination of lo-bi urea and other essential nutrients and crop protection products (phosphites) applied via foliar can be effective. This is a great way to get ahead and stay ahead of any deficiencies that might be present and also to boost tree health before and after flowering.

Vanessa Vicencio

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

vanessa.vicencio@yara.com

 

Vanessa Vicencio
Sales Agronomist

South Central Valley, California

(559) 909-5175

Previous Issues

Increase Fruit Set with Citrus Winter Fertilization

Closing the Season Strong with one Final Potassium Application

Potassium: Ensuring Higher Fruit Numbers and Higher Yields with YaraTera KMAX1

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