Michigan State University
On Jan. 1, 2012 phosphorus fertilizer applications to turfgrass in the state of Michigan were regulated according to Act 451 of 1994, Part 85 Fertilizers. Basically the amendments to the fertilizer act restricted phosphorus fertilizer applications to turfgrass unless a soil test indicated need or for new establishment. However, there were provisions that phosphorus fertilizer could be applied at 0.25 lbs. P/1000 sq. ft. if the source was a 'finished sewage sludge, organic manure, or a manipulated manure'. This provision resulted in many questions and some confusion about which natural fertilizers fell within this category.
On Tuesday, Nov. 5 Governor Snyder signed Public Act 151. This Act made revisions to Act 451 and in particular to phosphorus applications to turfgrass. The key addition was that the term 'natural fertilizer' was introduced into the language. Natural fertilizer is defined as a substance composed only of natural organic, natural inorganic, or both types of fertilizer materials and natural fillers. Public Act 151 has immediate effect, meaning today a person may apply biosolids, a natural fertilizer, or a manipulated manure to turf at a rate of not more than 0.25 lbs. P/1000 sq. ft./application. The addition of the term natural fertilizer certainly expands the number of fertilizers containing phosphorus fertilizer that can be applied. The key for the turf manager is understanding that the rate restriction of 0.25 lbs. P/1000 sq. ft./application is still in effect for these fertilizers so correct product calculations, calibration and application is critical to ensure applications don't exceed the 0.25 lb. P rate.