High Dose of Plant Growth Regulator Enhanced Lodging Resistance Without Grain Yield Reduction of Maize Under High Density

Lodging is a major constraint to maize productivity and harvesting mechanization in the North China Plain. EDAH (contains ethephon and diethyl aminoethyl hexanoate) is a novel growth regulator, which had been proved to enhance maize lodging resistance and increase yield, especially under high plant density. However, lodging still happens when recommended dose of EDAH was foliar sprayed in many previous reports. Therefore, a field experiment with normal dose (T1) and increased dose (T2) of EDAH was conducted to further enhance maize lodging resistance under different plant densities. Results indicated that T2 significantly reduced plant height and ear height, and obviously increased bending strength (P < 0.05), i.e., increasing EDAH dose more obviously enhanced maize lodging resistance. Concurrently, EDAH distinctly inhibited maize growth which resulted in lower leaf area index (LAI) and leaf area duration (LAD) after silking. However, both leaf photosynthetic rate and chlorophyll content during filling stage were not significantly (P > 0.05) changed by EDAH. Consequently, maize grain yields under T1 and T2 were reduced by 3.2-8.5% and 10.9-13.6% under optimized density (7.5 plants m(2-)) in this study, respectively. Nevertheless, EDAH did not reduce maize yield under high density (9.0 plants m(2-)) due to relative high LAI (5.3-5.6). We concluded that high dose EDAH further enhanced lodging resistance with reduced grain yield under optimized density, but maintained grain yield under high plant density. Results of this study provided a critical strategy to lower lodging risk and increase maize grain yield.