Simulated functional leaf area of USM Var5, DK 818 + Los Baños glutinous corn at grain filling stage

Corn genotypes DK 818, a hybrid and USM var 5, an open pollinated variety, were subjected to six defoliation treatments to attain different simulated leaf areas (FLAs) at two weeks after silk emergence (WASE)in the first trial. DK 818, USM var 5 and Los Baños glutinous were subjected to similar defoliation treatments at silk emergence in the second trial. Full defoliation above the ear reduced grain yield per plant by 44.0% at 2 WASE and 61.0% when leaf removals were done at silk emergence. Excision of all the leaves below the ear did not significantly reduce grain yield per plant when defoliation was done at 2 WASE, while there was marked reduction in grain yield (25.2%) when such level of defoliation was imposed at silk emergence. Removal of all the leaves above the ear at silking significantly shortened the ears, but this was not observed when all the leaves below the ear were excised. Removal of the topmost two or three leaves significantly reduced ear fill percentage. As expected, grain yield was higher with higher FLA. The linear relationship implied a narrow range of simulated FLAs or defoliations. Defoliation at silk emergence was more damaging to grain yield and yield components than defoliation at 2 WASE. DK 818 had relatively high yield and was more stable in producing grain per unit FLA regardless of the timing of defoliation. However, loss of FLA for this non-leafy genotype at an early stage of silking significantly reduced its grain yield. USM var5 had lower yield and efficiency of grain production per unit FLA under a more favorable condition (defoliation at 2 WASE). Defoliation at an early stage of silking produced comparable yield with DK 818, but its efficiency in producing grain per unit FLA remained low despite its leafiness. The Los Baños glutinous genotype was the lowest yielder and was the least leafy genotype. It had the lowest efficiency in producing grain per unit FLA. The leaves removed below the ear at 2 WASE onwards may have practical importance as soilage or feed herbage for ruminants.