Twice-spraying plant growth regulator EDAH stage-regulates maize plant morphology: a novel strategy for enhancing stalk lodging resistance.

Spraying the plant growth regulator EDAH (27% ethephon and 3% diethyl aminoethyl hexanoate) to enhance maize lodging resistance is a widely accepted practice in maize cultivation. In 2021-2022, single applications of EDAH at V6 (6 expanded leaves) and V12 (12 expanded leaves) were ineffective in preventing lodging (lodging rate, 21.76%-29.00%), though they did shorten internode lengths at the basal and middle-upper sections, respectively. Consequently, a twice-spraying regimen of EDAH at V6 and V12 was adopted in 2024-2025 to modify plant morphology. The effects of this twice-spraying were evaluated by determining grain yield and indicators related to stalk lodging resistance. Twice-spraying EDAH significantly improved stalk lodging resistance, reducing the lodging rate by 64.12%-79.28% and increasing grain yield by 2.26%-7.96%. This treatment simultaneously shortened the basal second to the fifth and middle-upper seventh to the eleventh internode lengths (by 21.07%-33.54% and 20.73%-32.76%, respectively), leading to significant reductions in plant height (20.67%) and ear height (23.90%), ultimately lowering the gravity height (19.06%). Leaf angles were also reduced, particularly at high planting densities. The primary mechanism by which twice-spraying EDAH reduced lodging rates was the optimization of plant morphology. The gravity height contributed 40.00% to lodging susceptibility. Twice-spraying EDAH enables staged regulation of maize stalk development, offering new insights and a production strategy for establishing dense-planted, stalk lodging-resistant, and consistently high-yielding maize populations.