Tomato plants generally benefit from bone meal, an organic fertilizer derived from ground animal bones. Bone meal serves as a natural, slow-release source of two nutrients important for tomato health and productivity: phosphorus and calcium. Using this amendment correctly supports robust plant development and a more abundant harvest. However, its effectiveness relies heavily on specific soil conditions and understanding its limitations.
The Essential Nutrients Bone Meal Provides
Bone meal is created by steaming and grinding animal bones into a powder or granular form, yielding a low-nitrogen fertilizer. It contains a significant concentration of phosphate, the form of phosphorus plants use. While the exact ratio varies, bone meal typically contains a high percentage of phosphorus, often ranging from 15% to 27%.
The other major component of this fertilizer is calcium, which makes up about 20% to 30% of its content. Bone meal functions as a slow-release amendment because its nutrients are not immediately water-soluble. Soil microorganisms and mildly acidic conditions must gradually break down the material to make the phosphorus and calcium available to the tomato roots over several months.
Maximizing Tomato Growth and Fruit Set
The phosphorus supplied by bone meal plays a direct role in energy transfer and metabolic processes within the tomato plant. Adequate phosphorus stimulates early and robust root development, anchoring the plant and improving its efficiency in water and nutrient uptake. A strong root system supports the plant for long-term productivity.
Phosphorus is also necessary for the formation of flowers and the subsequent development of fruit. By promoting healthy blooms, bone meal indirectly supports a higher fruit set, contributing to a more abundant yield. A sufficient supply of this nutrient can also influence fruit ripening, potentially reducing the number of green fruits remaining at the end of the harvest.
The calcium content in bone meal maintains the structural integrity of the plant’s cell walls. This strengthening effect helps regulate the movement of water and nutrients within the plant’s tissues. Blossom End Rot (BER), a common tomato disorder, is directly linked to a localized calcium deficiency within the developing fruit.
Ensuring the plant has access to calcium, particularly during the fruit development stage, is a preventative measure against BER. The calcium from bone meal helps stabilize cell membranes and ensures that new cells, especially in rapidly growing fruit, have the necessary building blocks. However, because of its slow-release nature, bone meal may not be a quick fix for an existing calcium deficiency.
Application Timing and Soil pH Requirements
The best time to apply bone meal to tomatoes is at the beginning of the growing season, specifically when transplanting seedlings into the garden. Gardeners should mix a small, measured amount, typically a tablespoon or two per plant, directly into the planting hole and blend it with the surrounding soil. This ensures the nutrients are placed immediately within the root zone for the young plant to access as it establishes.
Because bone meal is a slow-release fertilizer, one application at planting is often sufficient for the entire season. If an established plant shows signs of phosphorus deficiency, a light top-dressing can be worked into the surface soil around the base, taking care not to disturb the roots. Always follow the specific dosage instructions to prevent over-application, as excessive phosphorus can lead to other nutrient imbalances.
The effectiveness of bone meal is highly dependent on the soil’s pH level. Bone meal performs optimally in soil that is slightly acidic to neutral, ideally within the range of 6.0 to 7.0. In this pH range, the phosphorus remains soluble and available for the tomato plant to absorb.
A significant limitation arises in highly alkaline soils, which have a pH above 7.0. In these conditions, the phosphorus in the bone meal binds tightly with other minerals like calcium, a process known as “nutrient lockout.” This renders the phosphorus insoluble and unavailable to the tomato roots, making the application ineffective. Therefore, performing a soil test to confirm the pH and existing phosphorus levels is necessary before relying on bone meal as a fertilizer.