Nutrient Removal

A third approach to fertilizer recommendations still widely used is nutrient removal. Before the advent of soil testing, the nutrient removal approach to crop fertilization was the best science had to offer. Early agricultural scientists realized that crops obtained their nutrition from the soil and, to maintain good production, nutrients had to be returned to the soil. This was accomplished through crop residues, wood ashes, and manures. As a simple guideline to adding fertilizers, the nutrient removal approach is a major advance over not considering crop nutrition at all. The theoretical advantage of returning to the soil what is removed is that productivity is maintained and depletion avoided.

The disadvantage of this approach is that it does not account for the soil’s ability to supply many essential nutrients. Nutrient removal does not recognize that not all nutrients are used at 100 percent efficiency. A producer may under- or over-fertilize by following the nutrient removal approach. The most profitable fertilization approach needs to consider the cost of farm inputs and environmental concerns. Making fertilizer recommendations by relying on the crop nutrient removal approach ignores these two issues. In addition, a strict adherence to the nutrient removal approach makes soil testing unnecessary, since nutrients are added based on what is harvested.