Radiation use efficiency in maize as a function of sowing dates and plant densities

Resumo

The objective of this work was to evaluate the radiation use efficiency (RUE) for the accumulated biomass and for grain yield in the irrigated maize crop according to sowing dates (SOW) and plant densities (D) in Rio Largo, state of Alagoas, Brazil, in the year 2013. SOW were SOW 1 (6/28/13), SOW 2 (7/8/13), SOW 3 (7/18/13), SOW 4 (7/28/13) and the plant densities were D1 = 125,000, D2 = 87,500, D3 = 50,000, D4 = 37,500 plants ha-1. Sowing dates and the interaction of these dates with plant densities did not have significant effects on grain yield and RUE, but plant densities were significant. The highest average grain yield (6067.3 kg ha-1) occurred in D3, decreasing in the highest densities. RUE increased from 2.98 g MJ-1 in low density (D4) to 4.72 g MJ-1 in higher density (D1). The maize plants with higher densities showed a higher index of leaf area and dry biomass. At low plant density, the solar radiation incident is less intercept because the leaf area index is poorly distributed among the plant lines. The effect of plant density on RUE for the accumulation of biomass was the opposite to that of the RUE for grain yield (RUEy), so that lower RUEy was found at lower densities.