on enviromental impact of phosphates
Phosphate will stimulate the growth of plankton and aquatic plants which provide food for larger organisms, including: zooplankton, fish, humans, and other mammals. Plankton represent the base of the food chain. Initially, this increased productivity will cause an increase in the fish population and overall biological diversity of the system. But as the phosphate loading continues and there is a build-up of phosphate in the lake or surfacewater ecosystem, the aging process of lake or surface water ecosystem will be accelerated. The overproduction of lake or water body can lead to an imbalance in the nutrient and material cycling process (Ricklefs, 1993). Eutrophication (from the Greek - meaning "well nourished") is enhanced production of primary producers resulting in reduced stability of the ecosystem. Excessive nutrient inputs, usually nitrogen and phosphate, have been shown to be the main cause of eutrophication over the past 30 years. This aging process can result in large fluctuations in the lake water quality and trophic status and in some cases periodic blooms of cyanobacteria.
--- exerpted from https://www.water-research.net/phosphate.htm
I would say that because MN is the 'land of a thousand lakes', politicains and enviromentalists are hypersenstive about the conditions of thier lakes.
I will stand by my semi-organic stance that it is the over application of inorganic ferts and chems that have brought this issue to the forefront of MN politics, but I do not think that this is the only suspect.
How many of us are guilty of washing thier cars in the driveway and allow the run off to flow into the storm drains? Okay maybe fewer in this particular group then the general population
Point being that even though overapplication of chemical ferts my be the primary reason for the MN law, There are just as many other sources that are not AG related.
Does make a solid point for composting. Everything coming out of the land is going straight back in.