Which of the following is considered a high phosphorus availability fertilizer?

Superphosphate is recognized as a high phosphorus availability fertilizer due to its manufacturing process which involves treating rock phosphate with sulfuric acid. This process converts a significant amount of the phosphorus in the rock phosphate into a soluble form that plants can readily absorb. Consequently, superphosphate provides a quick source of phosphorus, promoting root development and enhancing plant growth, particularly in phosphorus-deficient soils.

Other fertilizers mentioned, such as rock phosphate and bone meal, typically contain phosphorus in forms that are less readily available to plants. Rock phosphate releases phosphorus slowly and often requires specific soil conditions, such as the presence of certain soil microbes, to become more available over time. Bone meal can provide a moderate source of phosphorus as it breaks down, but it doesn’t match the immediate availability provided by superphosphate.

Manure, while it contributes phosphorus, has variability in nutrient content and its phosphorus is often in organic form, requiring further decomposition before it becomes available to plants. Thus, in contrast to these other options, superphosphate stands out as a fertilizer with high phosphorus availability, making it an ideal choice for quickly addressing phosphorus needs in crops.