Stone Fruits

Nitrogen is a fundamental nutrient in stone fruit production, playing a critical role in tree vegetative growth, fruit development, and overall orchard productivity.  In young orchards, nitrogen is key in establishing vigorous growth to develop scaffold branches to support fruit growth in the coming seasons.  However, for many stone fruit varieties, once the trees are in full production, excessive nitrogen can cause more problems than it helps. Overapplication of nitrogen can stimulate excessive vegetative growth, leading to reduction of fruit size, and delayed maturity and color development.  It can also result in producing soft fruit with a reduced shelf life.  On the flip side, nitrogen deficiencies can result in pale foliage, reduced shoot growth, and poor fruit set.  A balanced nutrient plan, focused on rate and timing will help to optimize both yield and quality. Nitrogen should be applied early in the growing season to stimulate leaf and fruit development.  Avoid applying high rates of nitrogen late in fruit development.    

N-Sure® is a slow-release nitrogen fertilizer that contains Triazone-nitrogen.  Triazone is a stabilized nitrogen compound that releases nitrogen gradually over time, reducing the risk of leaching and volatilization losses. When blended with other nitrogen fertilizers like UAN solutions, and applied through fertigation systems, a consistent nitrogen supply can be supplied to the tree over time. N-Sure is also an excellent foliar fertilizer and can be tank mixed with other fertilizers and crop protection materials for convenience and efficiency (check compatibility before mixing). Thio-Sul® is Tessenderlo Kerley’s flagship product.  It contains nitrogen in the ammonium form, along with thiosulfate sulfur.  In situations where soil pH and/or bicarbonate levels in the irrigation water are high, Thio-Sul can be used as a tool to help manage these problems.  

Potassium is another vital nutrient for stone fruit production, influencing nearly every aspect of tree health and fruit quality. It regulates water movement within the plant, helps transport sugars to the fruit, and can help enhance size and color, which are also essential for marketability of stone fruit crops. Some evidence shows that potassium can also strengthen plant resistance to drought, disease, and cold stress, contributing to more resilient orchards and consistent yields.  Potassium availability is essential during fruit development to ensure proper fruit sizing, coloring and sugar content.  

Potassium thiosulfate (KTS®) is a highly effective potassium fertilizer for stone fruit growers. It delivers potassium in a liquid, readily available form that can be applied directly into irrigation systems, allowing for precise nutrient placement.  In addition to potassium, KTS supplies sulfur in the form of thiosulfate, which has been shown to help solubilize micronutrients like iron and manganese and can help to manage high pH soils.  K-Row 23® is another liquid potassium fertilizer.  K-Row 23 will allow for increased application rates, important especially when K applications are unexpectedly delayed, for example, by spring rain.  Also consider applying soluble potassium using KTS and K-Row 23 after harvest to ensure the tree has sufficient available potassium for early season growth coming out of dormancy. 

Calcium is a crucial nutrient in stone fruit production, essential for maintaining strong cell walls, improving fruit firmness, and reducing the risk of certain physiological disorders and internal fruit breakdown. It plays a key role in cell division and elongation, which supports healthy root, shoot, and fruit development. In stone fruit trees like peaches, plums, and cherries, adequate calcium levels contribute to better fruit quality, longer shelf life, and improved resistance to diseases and environmental stress. Calcium also enhances the structural integrity of plant tissues, helping trees withstand mechanical damage and reducing susceptibility to pathogens. Because calcium is relatively immobile in plants, consistent and targeted applications are necessary throughout the growing season. 

Calcium thiosulfate (CaTs®) is a highly effective calcium fertilizer for stone fruit orchards. It provides calcium in a soluble, plant-available form that can be applied directly through irrigation water. The thiosulfate component offers additional benefits by improving nutrient uptake efficiency and enhancing soil structure. It can also help reduce sodium buildup in saline soils, which is particularly valuable in regions with poor water quality. CaTs is compatible with many nitrogen fertilizers, making it easy to integrate into nutrient management programs. Its dual action supports both immediate calcium needs and long-term soil health, promoting high-quality, marketable fruit. 

Sulfur is an essential secondary nutrient in stone fruit production, playing a key role in plant metabolism and overall tree health. It is a critical component of certain amino acids and enzymes, contributing to protein synthesis, chlorophyll formation, and energy production. In stone fruit trees, sulfur supports vigorous growth, enhances disease resistance, and improves nutrient efficiency—particularly nitrogen. Adequate sulfur levels help maintain dark green foliage, which is vital for photosynthesis and fruit development. Sulfur also contributes to the flavor and aroma of fruit, making it important for both yield and quality. Deficiencies can lead to pale leaves, stunted growth, and reduced fruit set. 

Thiosulfate-based fertilizers, such as ammonium thiosulfate (Thio-Sul®), potassium thiosulfate, and calcium thiosulfate, are highly effective sources of sulfur for stone fruit orchards. These fertilizers provide sulfur in the thiosulfate form, which is readily available to plants and can be applied through fertigation or foliar sprays. Thiosulfates also improve the uptake of other nutrients, such as phosphorus and micronutrients, by modifying soil chemistry and enhancing root absorption. Thiosulfates can be a useful part of a program managing high soil pH. Their versatility and compatibility with other nutrients make thiosulfate-based fertilizers a valuable tool in balanced, efficient orchard nutrition programs. 

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