Right Source. Right Rate. Right Time. Right Place. This is the 4R Nutrient Stewardship program. Applying fertilizer using the 4R system allows a farmer to maximize the use of the fertilizer as well as reduce the amount used. The more knowledge a farmer has about when and where to apply nutrients can increase yields, reduce costs, limit negative environmental impacts, and potentially improve profits.
Below is a video from the Canadian Fertilizer Institute about 4R Nutrient Management which features Dr. Robert Coffin.