Historical changes in maize light extinction coefficient and light capture due to breeding and plant density

Identifying how maize (Zea mays L.) light interception has historically changed due to breeding and plant density can inform strategies to maximize future crop yields. We measured light interception at the top, middle, and lower canopy and derived the light extinction coefficient in 18 maize hybrids released by Bayer Crop Science between 1983 and 2017 in two environments in the US Corn Belt. Results indicated that at a constant plant density of 8.5 plants m⁻², breeding has decreased light interception at the top canopy by 0.51% year⁻¹, enhanced light capture in the middle canopy without affecting whole-canopy light interception. Newer hybrids at 8.5 plants m⁻² intercepted more light at the bottom canopy than older hybrids at 4.5 plants m⁻². We revealed a trade-off between breeding and plant density on light interception, in which the combination of both factors increased the total light interception by approximately 3%. The light extinction coefficient has decreased with the hybrid year of release by 0.5% year⁻¹ at 8.5 plants m⁻² (p = 0.15). Breeding and planting density had similarly contributed to decreasing light extinction coefficient. Present results enhance our understanding of historical changes in maize light interception as affected by breeding and plant density, which could inform future crop modeling and crop ideotype design studies.