Crop improvement through multidisciplinary approaches to different types of stresses‐law of the maximum

Abstract

The yield of a given crop is a function of all the variables or limiting factors imposed on the crop. These variables interact; and when the interaction is sequentially additive, they are adequately described by the Mitscherlich version of the Law of the Minimum. When synergistic interactions occur, it is because the Liebig version of the Law of the Minimum is in effect. With Liebig‐type stresses, no great response to yield can be obtained until the factor in greatest limitation is corrected. In contrast, with Mitscherlich‐type stresses, responses are in proportion to input and degree of deficit with predictable outcome. Order of input is of no physiological importance with Mitscherlich stresses so the emphasis may be placed on economics in choice of inputs. Successful diagnosis of problems in crop production requires that Liebig and Mitscherlich‐type stresses be identified as such since order of correction as well as decisions concerning which stresses are corrected depend upon the results. Especially when stresses are in Mitscherlich‐type limitation, numerical values of 1.00 or less can be assigned to each with 1.00 being no stress. Resulting yield will be the product of all stresses multiplied together. Inputs to overcome multiple Mitscherlich‐type limitations can result in large yield increases because of sequential additivity. Use of these concepts to develop high yields can be called the Law of the Maximum. The concepts can also be used to guide advances in biotechnology. Expectations for crop yields must variously consider the limitations imposed by land area, availability of capital and the environment.