Fig. 1. Relationship between percentage grain yield increase in response to reduction in row spacing and radiation interception (RI) observed in wide rows for maize (circles), soybean (triangles), and sunflower (squares). Radiation interception was expressed as percentage of incident radiation and measured at flowering in maize and sunflower and at R3 in soybean. Average standard errors of all experiments were 1.4 and 3.4% for x and y variables, respectively. Y = 42.85 - 0.45x; r2 = 0.60; p < 0.001.