Forage Responses of Maize Hybrids to Environmental and Management Variables.

Forage yield and quality of corn hybrids may be achieved through tall plants with low harvest index (HI) and relative low plant population (vertical yield) or through smaller plants with high HI, adapted to increased plant population (horizontal yield). Each morphotype (MT) would response in a different way according to the environment and management changes. The objective of this work was to study the response of each MT to different crop techniques in order to improve corn forage production and/or quality. In four Argentinean locations, two hybrids with different morphotypes, vertical yield with relative maturity (RM=130) and horizontal yield (RM=122), three planting dates (Early, medium and late), with three plant population (PP), 7, 9 and 11 pl×m^-2, and three harvest dates according to grain maturity (100% milky, 1/3, and 2/3 milkline) were evaluated. Ear (EY), stover (SY), and whole plant (WY) dry matter yield, HI, FDN, FDA and proteins (PRT) were measured. A factorial combined design with three replications was used. A mixed model was run, where environments were only considering randomized. Environment was the main variable, showing significant interactions with the rest of the variables. Delaying planting date EY decreased, SY increased, and decreased WY with no compensations of EY reduction, while PRT was not modified. No hybrid differential response was found, showing the importance of early planting dates. No MT×PP interactions were observed for WY and forage quality variables. However, significant differences between densities were observed through environments. EY increased and SY decreased when delaying harvest date, probably due to remobilization of photosynthates towards the ears, and FDA and FDN decreased owing to the greater contribution of the ear to the total forage production.