Growth and yield of irrigated maize under Mediterranean conditions: The effect of cultivar and plant density

A field study was conducted in a fully irrigated area (the Guadalquivir Valley, Southern Spain) with a typically Mediterranean climate in order to determine the effect of four different plant population densities (5.5, 7.5, 9.5 and 11.5 plants m(-2)) on the growth rate and yield of three maize cultivars (late, semi-late and medium) in 1993 and 1994. Total dry matter, leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), radiation use efficiency (RUE) and grain yield were determined. The avoidance of plant stress by irrigation and high solar radiation during grain filling ensured maintenance of an optimal photosynthetically active green leaf area until physiological maturity of the grain was reached. Average CGR and RUE values during grain filling (25.5 g m(-2) day(-1) and 2.92 g MJ(-1), respectively) exceeded those obtained during vegetative growth (23.7 m(-2) day(-1) and 2.28 g MJ(-1), respectively). The highest growth rate and yield (16 t ha(-1)) were provided by the late hybrid at a density of 9.5 plants m(-2). The results reveal maize crops to have a high potential yield on irrigated lands under Mediterranean conditions, and the underlying growth and yield formation patterns to differ from those for crops cultivated in temperate and tropical climates.