Fig. 3. Cumulative biomass as a function of the intercepted solar radiation of two cultivars of spring barley (Baronesse and Steptoe) at two densities in two years (2000 panels A and B, 2001 panels C and D) and seeding dates (first seeding date panels A and C, second seeding date panels B and D). The slope of the relationship between the two variables is the radiation-use efficiency (e). Flowering occurred when crops reached biomass levels between 400 and 550 g m^–2.