I was lucky to not have had to deal with someone who was OK to both throw away a company’s product and pollute, just because they could figure a way to get away with it.
One of the really good solutions to pollution was that a smart company used the waste in another process or sold it to another manufacturer who could make use of what was previously a waste and pollutant. It becomes a pollution issue when someone puts it in the environment, otherwise its just a processed or semi processed raw material.
That's quite common. 30 years ago when the cost of disposal at hazardous waste landfills rose sharply, you find away to blend in to virgin material, if you use disposal cost as a negative price. Back out the disposal cost from the raw cost, so you end up with a very low price product.
"or sold it to another manufacturer"
Same situation. Sell it cheap to a roofing tar manufacturer. You don't make a lot of money selling it to the roofing company but you avoided the hazardous waste disposal costs.
This all falls under the concept of pollution versus pollution streams. If the downstream price goes up, the material will divert from the upstream into a different stream.
This applies to that fertilizer running off. If there is a price to that run-off, it will take a different path. But in that case, the farmer saves money by avoiding the run-off costs plus he saves money by being more efficient with the fertilizer he actually uses.