Phosphorus Saturation Ratio (PSR) in Florida’s Sandy Soils
Phosphorus is an essential nutrient for crop production, but when it accumulates in soil beyond plant needs, it can become an environmental concern. One useful tool for assessing this risk is the Phosphorus Saturation Ratio (PSR), an indicator that measures the balance between phosphorus and the soil minerals that help retain it.
In a recent study led by Dr. Franky Celestin, PSR was evaluated across four common Florida cropping systems: grazed pastures, hayfields, row crops, and vegetable production systems. The results revealed substantial differences in phosphorus accumulation among these systems.
Vegetable systems exhibited the highest PSR values, followed by row crop systems, while grazed pastures consistently showed the lowest values. In fact, grazed pastures were the only system with a median PSR below the environmental threshold of 0.10, indicating a relatively low risk of phosphorus loss to surrounding water bodies.
These differences likely reflect long-term fertilizer management practices. Vegetable and row crop systems often receive greater phosphorus inputs to support production, which can lead to the accumulation of legacy phosphorus in soils over time. In contrast, grazed pastures generally receive fewer phosphorus inputs and are managed less intensively, resulting in lower phosphorus saturation levels.
Interestingly, traditional soil phosphorus measurements did not always reveal these differences among cropping systems. PSR, however, provided additional insight into the potential environmental risk associated with phosphorus accumulation.
The findings highlight the importance of nutrient management strategies that balance crop productivity with environmental stewardship.
Reference: Celestin, F., Maltais-Landry, G., Dubeux, Jose C.B., Mylavarapu, R., and Lin, Y. (2025). Cropping system is a key determinant of soil health after accounting for environmental and edaphic variability. Geoderma, 458, 117330. https://doi.org/10.1016/j.geoderma.2025.117330
