ABSTRACT
An evaluation of soil fertility is based on observations and tests of both plants and soils. Soils can be sampled and soil tested, and fertilizer recommendations developed before the growing season begins. Thus, soil test correlation experiments provide the information to correlate soil tests of various soils with the relative yield expected for various crops. Soil test correlation data are converted into descriptive terms and into useful interpretations. Many different soil test levels are differentiated, depending on need and situation. A method of evaluating crop nutrient status through the use of tissue analysis was developed by Beaufils called the diagnosis and recommendation integrated system. The Diagnosis and Recommendation Integrated System emphasizes the importance of nutrient balance within plant tissue and states that maximum yield may never be obtained unless the proper balance or ratio of nutrients is maintained in plant tissue. Norms have been developed for many of the agronomic crops, including corn, soybeans, wheat, sugarcane.
