Relationship of Radiation, Leaf Area Index and Crop Growth-Rate

Abstract

SHADING experiments, such as those by Blackman and Templeman1 on white clover, have shown the great reduction in crop growth-rate which occurs when light intensity is curtailed. A second factor influencing crop growth-rate is the leaf area index. There is evidence2,3 that the rate of dry matter production by a crop or pasture will increase as the leaf area index increases, until a maximum value is attained; thereafter as the index increases further, the rate of dry matter production will decline. This is presumed to occur because the lowermost leaves become so heavily shaded at high leaf area index that their photosynthetic contribution is less than their respiration.