A NOTE OF CAUTION CONCERNING THE RELATIONSHIP BETWEEN CUMULATED INTERCEPTED SOLAR-RADIATION AND CROP GROWTH

The interpretation of plant growth in terms of cumulated intercepted or absorbed solar radiation, and the efficiency with which this energy is used for dry matter production. has received much attention in the literature. Although the concept of plant radiation use efficiency is perfectly sound in theory, it may be difficult to use this technique predictively because the values for radiation use efficiency for a given crop may vary with site and season. Analysis and experimental data are used to demonstrate the methodological weaknesses of a simplistic interpretation of crop growth in terms of cumulated intercepted energy. When crop growth and radiation interception data are analyzed in a way that avoids these methodological weaknesses, the results show that under normal field conditions corp growth rates are not correlated with the rates of interception of solar energy. Also, although the oversimplifications of the early research have been recognized, we argue that there is still too much emphasis placed on the correlative relationship between cumulated intercepted energy and crop growth.