Non-leaching Phosphorus

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  • University of Florida stuides have demonstrated that the P in Milorganite is both plant available, and subject to much less leaching than P in triple super phosphate (TSP), a common P source in mineral fertilizers.

While Phosphorus (P) in run-off contributes to algae growth in lakes and streams, Milorganite has been exempt from numerous state P bans because it is considerably less likely to leach than chemical or synthetic fertilizers.

What is the role of Phosphorus (P)?

Phosphorus plays an important role in the photosynthesis process; essentially it helps the plant “breathe.”  Phosphorus aids in energy transfer and storage and helps plants efficiently use water.  Phosphorus is associated with root development and plants grown in soils lacking the proper amounts of P will not likely produce fully developed root systems. 

Phosphorus also plays a significant role in maintaining a healthy lawn, and a healthy lawn plays an even bigger part in keeping our waterways clean.  A thick, lush lawn acts as a filtration system cleaning and purifying water before it runs into our lakes.  Research shows that lawns fertilized with P contribute less run-off than lawns that have not received any fertilizer applications.  

Research indicates that Milorganite provides phosphorus, an essential nutrient for plant growth, without the leaching that is typical of mined Phosphorus sources.

Research conducted by University of Florida compared Milorganite's phosphorus to other fertilizer P sources.  The research showed that the leaching potential was greater with the synthetic fertilizer sources, and that Milorganite’s slow release P source provides sufficient amounts of P for plant growth, with very little P leaching.  This same research states that “Less than 20% of the total P applied leached for nitrogen based Milorganite treatments, suggesting that most Milorganite P is ultimately insoluble and will not leach.”

The Phosphorus in Milorganite is slow release, available to the plant as the plant requires it in adequate (but not excessive) amounts, therefore, making it less likely to leach.  Naturally occurring P is typically chemically bound up in the soil and not available for plant uptake.  Research indicates that naturally occurring phosphorus “binds” to the Milorganite and in turn becomes more readily available for plant uptake, and less likely to leach into rivers, lakes, and streams.

Responsible fertilization near waterways – 10 feet buffer zone

When fertilizing near a body of water do not fertilize within 10 feet of any waterway (ocean, lakes, rivers, streams, ponds).  Creating a buffer zone of grasses or natural vegetation along a shoreline helps prevent soil erosion and retain some of the nutrients that might otherwise enter a waterway.

Avoid fertilizing if heavy rain is expected, and never deposit fertilizer into waterways, wetlands or other bodies of water.   Sweep any excess fertilizer from impervious surfaces, such as driveways, streets and sidewalks, back into the vegetated area.

Phosphorus Runoff Research 

Brian Horgan, Ph.D., associate professor at the University of Minnesota and extension turfgrass specialist, explains the surprising results of a research study on water runoff and the use of phosphorus fertilizers.  This study demonstrates that properly fertilized lawns results in less phosphorus runoff.