At which soil pH would phosphorus be most available for plant uptake?

Phosphorus availability to plants is influenced significantly by soil pH. In general, the optimal soil pH range for phosphorus availability is between 6.0 and 7.0. Within this range, phosphorus is primarily present in forms that are easily accessible to plants.

At a pH of around 6.8, phosphorus is most likely to be soluble and available for plant uptake due to the balance between the solubility of phosphate ions and their tendency to form compounds with other elements in the soil. When the pH is lower, as in the case of pH 5.5, phosphorus can bind more readily with aluminum and iron oxides, making it less available to plants. Conversely, at higher pH levels, such as 7.5, phosphorus can become tied up with calcium, again reducing its availability.

Thus, a soil pH of 6.8 represents a sweet spot where phosphorus is maximally available for plant uptake, enabling better nutrient absorption and supporting healthy crop growth.