Leaf area, light interception, and crop development in maize

Few models used to estimate the fraction of photosynthetically active radiation intercepted by maize crops (fIPAR) as a function of leaf area index (LAI) account for genotype differences and ontogenetic stage. In this study, the development of the fIPAR/GLAI relationship of three maize hybrids having contrasting plant type and grown in different environmental conditions was characterized. Three field experiments were conducted at Rojas (34 degrees 08'S), Argentina, on a silty clay loam soil, without nutrient restriction. The effects of sowing date and water regime were tested. Plant density was always 7 plants m(-2). The fIPAR was calculated from measurements above and below the canopy, before and after maximum GLAI was attained. Hybrids differed significantly (P < 0.05) in individual leaf area, leaf angle, and GLAI evolution. Exponential models adequately described (r(2) > 0.77; n greater than or equal to 15) the fIPAR/GLAI relationship for pre-maximum GLAI data of all hybrids. Nevertheless, maximum fIPAR was always below values quoted in the literature (< 0.90), and differences were detected among hybrids in the attenuation coefficient (k) that were probably related to leaf angle and leaf area. For hybrids with a similar leaf angle at all leaf positions no difference existed in the fIPAR/GLAI relationship along the cycle (pre- and post-maximum GLAI). The relationship changed after tasselling for the hybrid with erect upper leaves. Ignoring such differences could be misleading when fIPAR/GLAI models are used to estimate canopy photosynthesis and hence biomass production, radiation-use efficiency, and kernel set of specific hybrids and growth stages.