Effects of the growing-maize canopy and irrigation characteristics on the ability to funnel sprinkler water

Stemflow is vital for supplying water, fertilizer, and other crop essentials during sprinkler irrigation. Exploring the spatial and temporal variations of crop stemflow and its influencing factors will be essential to preventing soil water and nutrient ion's migration to deeper layers, developing, and optimizing effective sprinkler irrigation schedules. Based on the two-year experimental data, we analyzed the variation patterns (stemflow amount, depth, rate, and funneling ratio) of maize stemflow during the growing season, and clarified its vertical distribution pattern. Meanwhile, effects of sprinkler irrigation and maize morphological parameters on stemflow were investigated. The results showed that stemflow increased gradually as maize plant grew. Specifically, stemflow was small at the pre-jointing stage and reached the maximum at the late filling stage. The upper canopy generated more stemflow than the lower canopy until the flare opening stage. After the tasseling stage, the middle canopy generated more stemflow than the other positions. Variation in canopy closure at different positions was the main factor contributing to the above difference. As sprinkler intensity increased, stemflow also increased. However, the effect of droplet size on stemflow was inconsistent. Specifically, when sprinkler intensity was less than or equal to 10 mm/h, stemflow was generated with increasing droplet size. In contrast, if sprinkler intensity was greater than or equal to 20 mm/h, stemflow tended to decreased with increasing droplet size. Compared with other morphological parameters, canopy closure significantly affected the generation of stemflow. Funneling ratio was not significantly affected by plant morphology. Based on the results of different sprinkler intensities, we developed stemflow depth versus canopy closure and stemflow rate versus canopy closure power function regression models with a high predictive accuracy. The research findings will contribute to the understanding of the processes of stemflow involving the hydro-geochemical cycle of agro-ecosystems and the implementation of cropland management practices.