Comparing the agronomic effectiveness of fertilizers on the basis of the rate of application: An interpretation

Several recently developed and marketed fertilizers containing S and/or Zn that have been evaluated for their agronomic effectiveness are often compared with the traditional standard fertilizers on the basis of a single high fertilizer rate of the tested nutrient in terms of crop yield. This approach can provide an inaccurate or misleading conclusion that they are as good as or even better than the standard fertilizer sources. A better and more accurate method is to compare the different fertilizer sources on the basis of multiple rates. In addition, measurements of the nutrient taken up by a crop can provide useful information to help achieve the objectives of a study.