Citrus fruit enlargement: N, K and Ca – the perfect trio!

July 2023

Summer has officially arrived, and the heat is also finally here. We have been so lucky here in the Central Valley with the weather this season. We had a very wet winter and spring. Even into May and June, we had very unseasonably cool weather. Citrus fruit is currently undergoing the fruit enlargement or fruit sizing growth stage and that means that essential nutrients such as nitrogen, potassium, and calcium are in high demand. Fertilizer applications are critical during this growth stage as well as managing heat stress as it can damage shoot and root growth.

Healthy, nutrient balanced citrus trees are more likely to pull through heat and other stresses than trees that suffer from nutrient imbalances or outright deficiencies.

During the critical growth stage of fruit enlargement in citrus, we see a major increase in the uptake of nutrients nitrogen, potassium, and calcium. Citrus trees require optimum nutrition at each growth stage to promote better fruit size, quality, and tree health. During fruit enlargement, nitrogen (N) and potassium (K) play a major role. Nitrogen is the nutrient with the strongest impact on growth. It influences fruit weight, peel thickness, and fruit acidity. Potassium is necessary for many plant functions such as the formation of sugars, protein synthesis, cell division and growth. Citrus fruit removes large amounts of potassium compared to all other nutrients. Further, potassium supports trees by reducing many stresses such as drought and heat stress via turgor pressure and stomata operation. Potassium also works with another macronutrient phosphorus to stimulate and maintain root growth in citrus trees. Deficiencies in potassium can lead to disease issues, decreased yields and fruit size while optimum levels can increase yields, fruit size, fruit weight and acid content. Potassium deficiency in citrus is made worse by acidic soils (low pH), soils rich in magnesium, and drought conditions. Sandy soils and high rainfall can also contribute to potassium deficiency due to leaching.

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Calcium (Ca) is a key nutrient for overall citrus tree health. It is essential for strong cell tissue and has a positive effect on yield, flowering, and fruit set. It can help crop roots thrive despite sodium damage. Soluble calcium improves soil structure by supporting aggregation and allowing for improved water infiltration and aeration. This increases the soil’s water holding capacity and improves the availability of soil moisture to plants. Optimum calcium nutrition in citrus can increase yields and supports more regular, uniform fruit size. Calcium deficiency leads to decreased fruit production as well as misshapen fruit. Citrus albedo breakdown, or fruit splitting, is one of the major causes of poor fruit quality. Both potassium and calcium help to reduce the incidence of fruit splitting and creasing on fruit quality, especially during the hotter months when fruit will be growing quickly under uniform irrigations.

Timing is critical for nitrogen, potassium, and calcium applications during the fruit enlargement growth stage. Available nitrate nitrogen and soluble calcium are important for plant growth, root health and result in increased water and nutrient absorption.

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  • 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


Contact your local Yara representative to find a YaraTera NITRAKAL MAX distributor near you.

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