Length‐Width Method for Estimating Leaf Area of Rice¹

Abstract The length‐width method for estimating leaf area has been evaluated with traditional Indica and Japonica rices ( Oryza saliva L.); the leaves of modern semidwarf rices, however, are quite different in shape. We therefore evaluated the length‐width method using 11,356 leaves taken from 2 semidwarf varieties grown under 3 fertilizer levels for 2 crop seasons. Measurement of length alone was unsatisfactory. The use of length times maximum width, however, was found satisfactory under most test conditions except at 30 days after transplanting and at maturity. In other cases, leaf area could be determined from K(L ✕ W), where L is the leaf length, W is the maximum width of the leaf, and K is 0.73 for dry‐season crops and 0.75 for wet‐season crops. This method is unbiased; estimates should have no more than 5% error.