Bone meal is a fertilizer derived from steamed and ground animal bones, valued for its high content of phosphorus and calcium. As a slow-release amendment, it provides a steady supply of these nutrients over an extended period in the soil. Bone meal offers a significant benefit to tomato plants, particularly in promoting strong initial growth and fruit development, but the timing of its application is important. Understanding when to apply this supplement can maximize its effectiveness, leading to a more abundant harvest and helping to prevent common physiological disorders.
Role of Phosphorus and Calcium in Tomato Growth
Phosphorus plays a central part in the energy transfer systems within the tomato plant, acting as a component of nucleic acids and adenosine triphosphate (ATP). For tomatoes, this nutrient is especially important for the development of a robust root system during the early stages of growth. Adequate phosphorus levels also support the generative phase of the plant, encouraging flower formation and successful fruit set, which directly impacts the final yield and quality of the crop.
Calcium is crucial for maintaining the structural integrity of the plant’s cells. It is incorporated into the cell walls, acting like a cement that holds them together and promoting cell division and root elongation. A steady supply of calcium is necessary to prevent the physiological disorder known as Blossom End Rot (BER), which appears as a dark, sunken spot on the fruit. This disorder occurs due to a localized calcium deficiency within the fruit, often caused by inconsistent water delivery or rapid growth, even when the soil has sufficient calcium.
Optimal Timing for Bone Meal Application
The most effective time for the initial application of bone meal is during the transplanting phase. Incorporating the powder directly into the planting hole ensures that phosphorus is immediately available to the young roots. Since phosphorus is largely immobile in the soil, placing it where the roots can access it right away encourages rapid root establishment, setting the foundation for the plant’s entire life cycle.
A second application, known as side dressing, is beneficial once the tomato plant shifts its focus from vegetative growth to reproduction. This usually occurs when the first flowers begin to appear or when the initial fruits start forming, signaling the plant’s high demand for sustained nutrients. For indeterminate varieties that continue to grow and produce fruit until the first frost, this mid-season boost ensures a continuous supply of phosphorus and calcium during the long, heavy-fruiting period.
The necessity of applying bone meal depends on the existing nutrient profile of the garden bed, which should be determined by a soil test. If a soil test indicates high phosphorus levels, adding more bone meal is unnecessary and could potentially disrupt the nutrient balance. Soil testing provides the most accurate context, helping to avoid over-fertilization and confirming a true deficiency that bone meal is intended to correct.
Proper Application Methods and Caution
When applying bone meal at transplanting, use one to two tablespoons for each planting hole. It is important to mix the measured amount thoroughly with the soil at the bottom of the hole before the tomato plant is set in place. Direct contact between concentrated bone meal and the tender young roots should be avoided, as this can cause damage to the plant tissue.
For mid-season side dressing, approximately one tablespoon per plant should be sprinkled in a circle around the base, keeping it a few inches away from the main stem. The bone meal must then be gently worked into the top inch or two of the soil and watered in well to begin the slow process of nutrient breakdown and release. Since bone meal is not water-soluble, it relies on soil moisture and microbial activity to break down, which is why mixing it into the soil is important for effectiveness.
Over-application can create a phosphorus buildup in the soil over time. Excessive phosphorus can interfere with a tomato plant’s ability to absorb other micronutrients, specifically zinc and iron, leading to deficiency symptoms like yellowing leaves. Furthermore, bone meal is most effective in slightly acidic to neutral soil, typically with a pH below 7.0. In highly alkaline soil, the phosphorus within the bone meal can become chemically bound and unavailable to the plant roots, making its application less useful.