Efficiency of Maize Dry Matter Production During Periods of Complete Leaf Area Expansion

Abstract

AbstractCrop dry matter production, in the absence of other limiting factors, is determined by the absorption of photosynthetically active radiation (PAR) by a crop canopy and the efficiency with which absorbed PAR is converted into dry matter. This study was conducted to investigate the effects of plant density and phase of development on PAR absorption and conversion efficiency of two maize (Zea mays L.) hybrids. The maize hybrids Pioneer 3851 and Pioneer 3925 were grown in 1984 and 1985 at plant densities of 3.9, 6, and 10 plants m−2 in irrigated field experiments near Elora, Ontario, on a London loam (Aquic Hapludalf) soil that had been systematically tile drained. Conversion efficiency was estimated from rates of aboveground dry matter accumulation and PAR absorption from approximately 2 wk before to 6 wk after silking. PAR absorption was estimated from continuous measurements of incident PAR, PAR reflectance and PAR transmittance. Crop growth rates declined during the phase of development under study due to a decline in incident PAR and a decline in conversion efficiency from 5.8 to 3.5%; PAR absorptance was approximately 89% and remained fairly stable. Leaf area index among density‐hybrid treatments ranged from 2.0 to 4.8, and PAR absorption of the latter was 9% higher than that of the former. Although crop growth rates of the plant densities were not different during the grain‐filling period, differences in PAR absorption were too small to show a significant effect of plant density on conversion efficiency. Photosynthetic conversion efficiency appears to be influenced by phase of development, but the effects of plant density on efficiency appear to be small.