Relative Maturity on Maize: Does It Really Represent Duration of Maize Growth Period?.

Knowledge of phenological stages duration in maize allows elucidating the effect of factors that affect grain yield and adjusting specific agronomic practices for avoiding them. Estimation of relative maturity (RM) has been used by breeding programs as tool for hybrids selection, as it has been considered by farmers as a relevant trait for maize production systems. However, the RM does not indicate the duration of specific periods along crop cycle, such as vegetative or reproductive periods. This information is relevant for understanding genotypic differences in grain yield, especially for a group of hybrids with close RMs. Several experiments were conducted during 2010 and 2013 in order to identify genotypic differences in (i) duration of several phenological stages: sowing to emergency, emergency to anthesis, anthesis to silking, effective grain filling period (from R2 to physiological maturity), and dry down period, (ii) morphological trait: total leaf number, plant height, and ear height, and (iii) yield components: kernel number (GN) and kernel weigh (KW). Experiments included a combination of irrigated and non-irrigated conditions, and planting dates (early and late planting).Experimental designs were randomized complete design. Relevant temperate commercial hybrids of Argentina with different RM were evaluated (10 hybrids). Differences in RM among hybrids were mainly related to dry down duration, and in a lesser extent, to vegetative and reproductive phase duration. There was a wide range of variation in KN and KW among hybrids with similar RM. Contrary to most evaluated stages, dry down phase was highly affected by environmental factors (temperature, relative humidity and vapor pressure). In conclusion, RM could only be used as criteria for determining genotypic differences in grain moisture for a specific time.