Citrus

Nitrogen is a vital nutrient in citrus production, playing a key role in vegetative growth, fruit development, and overall orchard productivity. In young citrus orchards, nitrogen supports vigorous canopy growth and root development, helping trees establish a strong framework for future fruiting. However, once trees reach full production, nitrogen management becomes more nuanced.  Excessive nitrogen can lead to overly vigorous vegetative growth, which may reduce fruit size and can delay maturity. On the other hand, nitrogen deficiencies can cause pale foliage, weak shoot growth, and poor fruit set. Achieving the right balance both in rate and timing is essential to optimize yield and fruit quality. 

Nitrogen should typically be applied early in the season heading into bloom time, to stimulate leaf flush and fruit set. Avoid heavy applications later in the season, as they can negatively impact fruit development and postharvest performance.  Also, avoiding nitrogen application in the fall can reduce damage to young flush during winter frosts.   

N-Sure® offers a slow-release nitrogen source containing Triazone-nitrogen.  When blended with other nitrogen sources like urea and UAN-32, N-Sure enhances the blend by providing a steady supply of nitrogen to the crop, while minimizing leaching and volatilization. It’s effective when applied through fertigation or surface banded.  One of the best ways to apply N-Sure to citrus crops is via foliar application. Research has shown the benefit of foliar applied triazone to citrus, resulting in sustained leaf tissue N throughout the growing season. N-Sure is also compatible with other fertilizers, including micronutrients, as well as many crop protection products (ensure compatibility before tank mixing). 

Thio-Sul®, Tessenderlo Kerley’s flagship product, delivers ammonium nitrogen and thiosulfate sulfur, two nutrients essential for chlorophyll production and plant metabolism. In addition to improving nitrogen use efficiency and managing citrus groves with high soil pH or bicarbonate-rich irrigation water, Thio-Sul has shown promise in helping combat citrus greening disease (HLB). By enhancing nutrient uptake and improving root zone conditions, Thio-Sul can extend the production life of greening affected citrus.  

Potassium is a critical nutrient in citrus production, influencing nearly every aspect of tree health, fruit development, and overall orchard performance. It plays a central role in regulating water movement within the plant, activating enzymes, and facilitating the transport of sugars from leaves to fruit. In citrus, potassium directly affects fruit size, rind thickness, juice content and internal quality, all factors that improve marketability. During key growth stages, especially fruit set and enlargement, potassium availability becomes even more important. Deficiencies during these periods can lead to small, misshapen fruit, poor color development, and reduced sugar accumulation. Potassium can also contribute to the tree’s ability to withstand environmental stressors such as drought, salinity, and cold snaps, helping maintain consistent yields across variable seasons. 

Potassium thiosulfate (KTS®) is a highly efficient potassium source for citrus growers. Delivered in liquid form, KTS is ideal for fertigation, allowing for precise nutrient placement and immediate uptake. It also supplies thiosulfate sulfur, which helps solubilize micronutrients like iron and manganese. Thiosulfate is especially beneficial in high-pH soils, which are common in many citrus-growing regions. K-Row 23®, another liquid potassium fertilizer, offers flexibility for higher application rates, particularly during the fruit bulking stage. 

Calcium is another important nutrient in citrus production, essential for maintaining strong cell walls, improving fruit firmness, and reducing the risk of internal fruit disorders. It plays a vital role in cell division and elongation, supporting healthy root, shoot and fruit development. In citrus, adequate calcium levels are directly linked to improved rind strength, better postharvest quality, and longer shelf life, key factors for both fresh market and processing fruit.  Calcium also enhances the structural integrity of plant tissues, helping citrus trees resist mechanical damage from wind or harvest operations and potentially reducing susceptibility to pathogens like Phytophthora and Alternaria. Because calcium is relatively immobile within the plant, consistent and well-timed applications are necessary throughout the growing season, but especially important during bloom and early fruit set, to ensure it reaches developing fruit. 

Calcium thiosulfate (CaTs®) is a highly effective calcium fertilizer for citrus growers. It delivers calcium in a soluble, plant-available form that can be applied through fertigation systems for precise placement. The thiosulfate component improves nutrient uptake efficiency and helps solubilize micronutrients like iron and manganese, especially important in high pH soils common in many citrus-growing regions. CaTs can also help mitigate sodium buildup in saline soils and offset the negative effects of bicarbonate-rich irrigation water. It’s an effective tool in helping improve citrus groves with issues related to water infiltration. CaTs is compatible with many nitrogen fertilizers, which makes it easy to integrate into citrus nutrition programs, supporting both immediate calcium needs and long-term soil health for high-quality, marketable fruit. 

Sulfur is an essential secondary nutrient. In citrus production, sulfur plays a vital role in plant metabolism, nutrient uptake and overall tree vigor. It is a key component of amino acids and enzymes involved in protein synthesis, chlorophyll formation, and energy transfer. In citrus trees, sulfur supports robust vegetative growth, enhances disease resistance, and improves the efficiency of nitrogen utilization, making it important in balanced nutrition programs. Adequate sulfur levels help maintain dark green foliage, which is crucial for photosynthesis and fruit development. Deficiencies can result in pale leaves, stunted growth, and poor fruit set, often resembling nitrogen deficiency but requiring a different management approach. 

Thiosulfate-based fertilizers, including Thio-Sul (ammonium thiosulfate), KTS (potassium thiosulfate), and CaTs (calcium thiosulfate), are highly effective sulfur sources for citrus orchards. These products deliver sulfur in the thiosulfate form, which is readily available to plants and suitable for fertigation. Thiosulfates enhance the uptake of other nutrients, such as phosphorus and micronutrients, by modifying soil chemistry and improving root absorption. They also help buffer high soil pH and mitigate the effects of bicarbonate-rich irrigation water, common in many citrus-growing regions. 

Importantly, thiosulfate-based fertilizers can play a supportive role in managing citrus greening disease (HLB). HLB-infected trees often suffer from impaired nutrient transport and root decline, making efficient nutrient delivery critical. Thiosulfates improve root zone conditions and nutrient solubility, helping trees absorb essential elements more effectively even under disease stress. When integrated into a precision nutrient management program, thiosulfates can contribute to improved canopy health, better fruit retention, and more consistent yields in HLB-affected groves. 

• Thio-Sul® - 12-0-0-26S
• CaTs® - 0-0-0-10S-6Ca
• KTS® - 0-0-25-17S
• N-Sure® - 28-0-0