Plant population and xrop yield

Abstract

UNDER the above title, Holliday1 has recently published an equation which describes in a number of cases the relationship between yield and density in crop plants. In its simplest form this relationship is : Where w is the yield per plant, ρ is the number of plants per unit area and A and B are constants. This equation was used (with these symbols) by Shinozaki and Kira2 in 1956. An equivalent relationship connecting the total yield per unit area, y = ρw, with the spacing per plant, s= 1/ρ, namely : Was proposed independently be De Wit and Ennik in 1958 3. These authors concede that the formula may not apply at high plant densities, and Holliday has directed attention to its limitations at very low plant densities, and accordingly has proposed a modification of equation (1). Appropriate modifications for both extremes are considered by Shinozaki and Kira2. Holliday further points out that even his modified equation cannot describe adequately total yield/plant density relationships where the form of the curve is parabolic, that is, where a certain plant population gives higher yields than either lower or higher populations. This type of curve, it is claimed, is typical of situations where yield is a function of reproductive growth, whereas curves that reach a stable maximum with increasing plant density are typical of yield of vegetative growth, and are defined by equations similar to or derived from equation (1). © 1960 Nature Publishing Group.