Maize hybrid yield and physiological response to plant density across four decades in China

Abstract The popularity of density‐tolerant maize ( Zea mays L.) hybrids greatly increased the yield of maize hybrids in China in recent years. Clarifying trends in yield and plant density responses of agronomic characters of maize hybrids released in different years can provide theoretical and practical guidance for breeding high‐yield and density‐tolerant maize hybrids. The results showed grain yield (GY) of maize hybrids released in the 1970s and 1980s decreased with increased plant density. But GY of maize hybrids released in the 1990s and 2000s increased with a plant density increase. The GY gains from the low to high plant density plots were 86, 135, and 198 kg ha –1 per year, respectively. In all plant density treatments, yield and biomass of newer hybrids (2000s) were significantly higher than those of older hybrids (1970s). The leaf area index (LAI) of maize hybrids released in different years (1970s ∼ 2000s) increased with plant density, whereas the extinction coefficient decreased. Compared with the old hybrids, new hybrids have larger population sink capacity and stronger source supply ability, which is more prominent under high density. Population sink capacity is the main factor limiting maize yield. The key to maize hybrid improvement is to increase the population sink capacity. Breeders should continue to select for hybrids under stressful and high plant density conditions to increase seed setting rate and decrease empty ear rate of maize hybrids.