Calcium Fertilizers

While calcium (Ca) is classified as a secondary macronutrient, its critical roles in plant structure, nutrient uptake, enzyme activation, stress tolerance, and produce quality underscore its importance in optimizing crop productivity and sustainability. It even helps convert nitrate-nitrogen into forms needed for protein formation.

Calcium is immobile. It is primarily supplied to plants through soil and foliar applications in various forms, such as calcium carbonate, calcium nitrate, calcium chloride, and polyhalite – a sulfur-based multi-nutrient containing 12.2% calcium sulfate. Available calcium can also alleviate symptoms of aluminum toxicity.

Why is calcium so vital to plant growth?

Calcium is an essential crop nutrient vital for many aspects of crop development.

• Structural Integrity: It forms a vital component of plant cell walls, ensuring their strength and stability, which are essential for maintaining plant architecture and overall health.
• Enzyme Activation: Calcium activates numerous enzymes crucial for plant growth and metabolism. These enzymes drive essential biochemical reactions such as photosynthesis, respiration, and protein synthesis.
• Nutrient Uptake: It facilitates the uptake and distribution of other essential nutrients within the plant. By regulating ion movement across cell membranes, calcium enhances the absorption of nutrients like nitrogen, potassium, and magnesium.
• Stress Tolerance: Adequate calcium levels enhance plant resilience to environmental stresses such as drought, heat, and diseases. It helps maintain cell membrane stability, thereby improving overall stress management capabilities.
• Quality & Shelf Life of Produce: Calcium influences the quality attributes of harvested fruits and vegetables. It promotes firmer texture, reducing the incidence of disorders like blossom end rot in tomatoes and peppers, and thereby enhancing marketability and shelf life
• Rooting & Fruiting: Calcium helps stimulate root growth and improve root structure, enhancing nutrient uptake efficiency. It also promotes proper fruit formation and reduces disorders like blossom end rot in tomatoes and peppers.

Symptoms of calcium deficiency

Calcium deficiency in crops results in poor root growth and the death of the root tips. A lack of calcium will make the crops vulnerable to diseases, including blossom end rot in tomatoes, tip burn in cabbage, and black heart in celery.

Calcium is immobile within the plant, so if the supply of new calcium ceases, or is restricted, deficiency symptoms will appear on younger leaves. New leaves become distorted, with curled edges, and the growing tip may die. Learn more about calcium deficiency here!

How is calcium linked to physiological issues and disorders?

Inadequate calcium availability during rapid fruit growth can lead to insufficient calcium deposition in developing tissues. Calcium fertilization is crucial for preventing physiological issues in plants by supporting cell wall integrity, enhancing stress tolerance, improving nutrient uptake, and promoting overall plant health and fruit quality.

Bitter Pit: Proper calcium levels contribute to improved quality attributes such as texture and firmness. It reduces the occurrence of disorders like bitter pit in apples, where calcium deficiency leads to cell collapse and tissue breakdown post-harvest. This enhances the marketability and shelf life of produce.

Disorders like Blossom End Rot: In fruits such as tomatoes and peppers, blossom end rot occurs due to calcium deficiency in developing fruit tissues. Calcium fertilization helps prevent this disorder by ensuring sufficient calcium is available during fruit development, thus reducing the incidence of physiological breakdown and lesions at the blossom end.

Using calcium fertilizers to supplement soil calcium levels and address specific crop needs can help prevent deficiencies and reduce the risk of crop loss due to physiological disorders.

Common Challenges with Calcium Fertilization

• Soil pH and Availability: Calcium availability varies with soil pH; acidic soils may hinder calcium uptake.
• Application Timing: Timing applications to coincide with plant demand, especially during peak growth stages.
• Application Methods: Choosing between soil application (broadcasting, banding) and foliar spraying based on crop needs and soil conditions. Polysulphate, high in plant-available calcium sulfate, is an ideal granular choice (for spring or fall application), compatible with commonly used MAP, DAP, and KCL in a physical blend. We like to include options like Agrolution High K CalMag 11-6-20 +6Ca +1.5Mg for water-soluble and acidifying options to provide balanced nutrition during reproductive stages.
• Nutrient Interactions: Balancing calcium application with other nutrients like magnesium, potassium, and phosphorus to avoid deficiencies or imbalances.
  • Ca Interaction with Magnesium: Competes for uptake sites; excessive calcium can reduce magnesium uptake.
  • Ca Interaction with Potassium: Influences potassium availability and uptake efficiency.
  • Ca Interaction with Phosphorus: Forms insoluble compounds in high pH soils, reducing phosphorus availability.

Addressing these challenges requires strategic fertilization practices tailored to local soil conditions and crop requirements.

Calcium: Do You Have Too Much or Too Little

Regions and soil types across the US that are prone to calcium deficiencies or excesses influence our recommendations and practices.

Calcium Deficiency:

1. Acidic Soils: Regions with naturally acidic soils tend to have lower calcium availability due to increased leaching and reduced soil pH, which hinders calcium uptake by plants. Examples include parts of the Southeastern United States and some areas in the Pacific Northwest. We often recommend incorporating pH balanced Polysulphate to acidic soils as a multi-nutrient source of Ca.
2. High Rainfall Areas: Areas with high annual rainfall may experience increased leaching of calcium from the soil profile, leading to deficiencies over time. This can occur in regions along the Gulf Coast and in parts of the Northeast. Mitigating this by applying calcium in the right rate, form, place and time (the 4R of nutrient stewardship) can help offset nutrient losses and ensure the fertilizers we put down are available to be taken up. Soil and tissue testing can also help determine if mid-season applications are required to address deficiencies.

Excess Calcium:

• Calcareous Soils: Regions with calcareous soils, which contain high levels of calcium carbonate (lime), can experience issues with excess calcium. These soils often have elevated pH levels (alkaline) that can inhibit the availability of other essential nutrients like iron, manganese, and zinc. Examples include parts of the Great Plains, the Southwest, and some areas in California. Acidifying fertilizers, like Nova PeKacid and Agrolution pHLow are designed to help improve nutrient uptake in calcareous soils, and are highly compatible products easily integrated into fertigation and foliar applications.
• Saline Soils: Some saline soils can also have elevated calcium levels, often in the form of calcium sulfate (gypsum). While not necessarily toxic, high calcium levels in saline soils can affect soil structure and nutrient availability, impacting crop growth and productivity. In regions with high levels of bicarbonates in the soil the calcium in Polysulphate can help to create the balance needed to reduce salinity in soil.

Management Considerations:

• Soil Testing: Regular soil testing is essential to monitor calcium levels and adjust fertilization practices accordingly.
• pH Management: Managing soil pH is crucial for optimizing calcium availability. In acidic soils, liming can help raise pH and improve calcium uptake by plants. In calcareous soils, acidification strategies may be necessary to enhance nutrient availability.
• Crop Selection and Varietal Tolerance: Selecting crop varieties that are tolerant to specific soil conditions (e.g., acidic or alkaline soils) can help mitigate calcium-related challenges.

Understanding regional soil characteristics and conducting thorough soil analysis is key to effectively managing calcium levels. This knowledge allows us to implement targeted fertility management practices that optimize calcium availability for crop production while mitigating potential issues associated with deficiencies or excesses.

Overall, calcium’s role in agriculture extends beyond mere nutrient provision, impacting plant structure, function, and resilience. It contributes significantly to farm productivity and profitability. Building a balanced fertility program is essential to not only crop production, but fertilizer return on investment. Reach out to our agronomy team and let us know how we can help you with your calcium related questions.