Delaying the application of plant growth retardant can simultaneously increase maize yield and water productivity

Improving water productivity (WP) is critical for maize production. Delaying the application of plant growth retardants (PGRs) from V7 (7th leaf collar visible) to V14 can simultaneously enhance maize yield and lodging resistance. However, the effects of delaying PGRs on maize WP are still unclear. A three-year field experiment was conducted by applying EC (a mixture of ethephon and cycocel) at V7 (TV7) and V14 (TV14), respectively, to clarify the effects of EC on plant architecture, root system architecture, water consumption, and yield in maize. Over three years, TV7 significantly reduced plant height, ear height, and leaf area index (LAI), while TV14 only significantly reduced plant height but almost did not reduce ear height or LAI. Specially, TV7 mainly reduced the area of functional leaves that were around ear, which resulted in lower biomass and yield. In contrast, TV14 shortened the distance between upper leaves and ear, which increased proportion of assimilates partitioned to grains (15.76 %) and grain yield (20.92 %) compared with CK. Additionally, both TV7 and TV14 promoted root growth, showing higher root length, root surface area, especially for TV7. However, the increased root did not increase maize evapotranspiration. Partial least squares analysis and correlation analysis demonstrated that reduced LAI was beneficial to reducing water consumption during the maize growth period. Finally, WP was increased by 24.88 % under TV14 compared with CK. Collectively, these findings provided a pathway to improve maize yield and WP simultaneously. • EC (a mixture of ethephon and cycocel) reduced maize leaf area but increased root growth. • Spraying EC at 14-leaf stage increase maize yield by promoting biomass allocation to ear. • Spraying EC at both 7-leaf stage and 14-leaf stage can reduce ETc. • Spraying EC at 14-leaf stage increased maize water productivity.