Description:
Accurate crop growth and radiation use efficiency (RUE) measurements under optimal growth conditions are required to predict grain yield near the genetic growth potential and estimate climate change effects on crop production. Research was conducted to quantify RUE of maize during the whole growth period, vegetative period (VP, phenological development stage DVS < 1.0), and reproductive period (RP, DVS ≥ 1.0) under the optimal growth condition in Northeast China. Maize was grown in three population density treatments (9.0, 7.5, and 6.0 plants m -2 , referred to HD, MD, and LD respectively) over three growing seasons (2017–2019). The maximum Leaf Area Index (LAI) was observed after the anthesis period (DVS=1.2), ranged from to 4.9 to 6.9, and then gradually decreases. Photosynthetically active radiation (PAR) intercepted by the canopy of maize was approximate 10% during the early stage of the vegetative period (DVS < 0.3). Then greatest differences occurred during the late vegetative period (DVS = 0.3 to 0.8). When DVS > 1.0, there is no significant difference between the three population density conditions. Estimates of RUE were obtained based on the intercepted PAR (IPAR) and absorbed PAR (APAR). Based on APAR, RUE decreased 4.09, through 3.94 to 3.79 g MJ -1 in the whole growth period as planting density decreased from HD, MD to LD. Based on IPAR, RUE values were 3.86, 3.60, and 3.56 g MJ -1 , respectively. Moreover, maximum RUE occurs during VP and declines during RP. The maximum RUE value, 4.09 g MJ -1 , should be used in the maize simulation model for predicting potential yield under 9.0 plants m -2 planting density