Maize yield and quality in response to plant density and application of a novel plant growth regulator

Farmers in China have gradually increased plant density in maize to achieve higher yields, but this has increased risk of lodging due to taller and weaker stems at higher plant densities. Plant growth regulators can be used to reduce lodging risk. In this study, for the first time, the performance of a mixture of the plant growth regulators ethephon and diethyl aminoethyl hexanoate (DA-6), called EDAH is tested at different plant densities and in different cultivars. Grain yield, yield components and grain quality as well as plant height and lodging percentage were determined in two years (2012 and 2013), using two maize hybrids, ZD 958 and Pioneer 335 at densities of 4.5, 6.0, 7.5 and 9.0 plants m-2 with and without foliar application of EDAH at 7 expanded leaves stage. EDAH significantly increased grain yield (by 7.8–8.0%), kernel number per ear (by 2.9–4.0%) and 1000-kernel weight (by 3.3–5.1%). Lodging percentage increased with plant density and was decreased by EDAH application in 2013. Optimal density was 7.5 plants m-2. The number of ears per unit ground area increased linearly with plant density, but number of kernels per ear and kernel weight showed an optimum. The two tested cultivars differed in yield and quality. No effects of EDAH on grain quality parameters (protein, oil and starch content) were found. We conclude that EDAH can improve lodging resistance and yield in maize, and that the yield effect of EDAH also occurs if lodging is not reduced.