Removing top leaves increases yield and nutrient uptake in maize plants

Abstract: Intraspecific competition for light affects nutrient uptake of maize, especially during the seed filling phase (from the blistering-stage to physiological-maturity). Partial leaf removal only affects the top leaves and improves the light-environment, which could then enhance nutrient uptake during the seed filling phase. However, there is a shortage of quantitative information on the yield effects of such a management measure. A 3-year field trial was conducted to evaluate the impact of different leaf removal treatments (no removal of leaves (D0: control), removal of two leaves (D2), removal of four leaves (D4), and removal of six leaves (D6) from maize-canopy) on total dry matter accumulation, and nitrogen, phosphorus, and potassium uptake at the blistering-stage and physiological-maturity, plus seed number per plant, seed weight, and seed yield at physiological maturity. Compared to D0, at physiological-maturity, D2 significantly increased total dry matter accumulation (by 9%), and uptake of nitrogen (by 5%), phosphorus (by 10%), and potassium (by 4%); while excessive leaf removal treatments considerably reduced dry matter accumulation and nutrient uptake. Importantly, during the seed filling phase of maize, treatment D2 significantly enhanced the uptake of nitrogen, phosphorus, and potassium by 76%, 40%, and 65%, respectively, compared to control. Treatment D2 increased seed number per plant (by 6.4%, from 448 under D0 to 477 in D2) and seed weight (by 5.7%). Relative to control, maize in D2 had 12%, 14%, and 11%, higher seed-yields in 2017, 2018, and 2019, respectively, and it also improved the economic profit when taking into account labor costs. Graphic abstract: Graphical representation of changes in light transmittance, photosynthesis, nutrient uptake, carbohydrate, and dry matter accumulation in maize plants as affected by different leaf removal treatments. Treatment codes represent no defoliation (D0: control), removal of two leaves (D2), removal of four leaves (D4), and removal of six leaves (D6) from the top of maize canopy. Yellow and green arrows show the light environment and leaf area of maize plants. The black arrows represent the regulating directions of leaf removal treatments on maize growth and development in this paper. The graphical abstract clearly demonstrates the significant improvement of optimum leaf removal treatment (D2) as compared to control (D0). The red and blue arrows show the relevant increase and decrease of the mentioned components between the optimal leaf removal and control. [Figure not available: see fulltext.