Grain Yield and Silage Production of Grain and Silage-Specific Maize Hybrids at Different Plant Population Densities and Sowing Dates.

Despite of the increased use of silage-specific maize hybrids, studies of the physiological process involved in digestible biomass production are rare. More over, several double-purpose maize hybrids are alternative used for silage and grain production. We have made a comparative study of biomass production, the nutritive value of plant biomass and grain yield, of two maize genotypes (a silage-specific hybrid, and a grain-specific one; SH and GH, respectively), cultivated at three plant population densities (6, 9, 12 pl m^-2) and 9 pl m^-2 with restricted kernel set and two sowing dates (September and December). Field experiments were conducted at Paraná (33.43S 59.15W), Argentina, without water and nutrient limitations. Both light capture and radiation use efficiency of the SH resulted greater (ca. 13%) than those of GH and were reflected on total biomass production and grain yield. Maximum plant biomass productions of both genotypes were recorded at the same plant population density (12 pl m^-2 and 9-12pl m^-2 for September and December sowings; respectively). At these stand densities, canopy size resulted greater than critical LAI value for maximize light interception. Optimum plant population density, however, differed between genotypes (9-12 pl m^-2 and 12 pl m^-2 for SH and GH; respectively). Digestible biomass production was affected by sowing date, hybrid, population density and kernel set. For both hybrids the greatest biomass production, grain yield and biomass digestibility were recorded in September sowing. Biomass digestibility of SH was greater than that of GH. This trait was modified by plant population density, ontogeny and kernel set. For both hybrids and sowings the digestible plant biomass was enhanced in response to increased plant population density, because of the higher plant biomass production overcompensated the lower digestibility value. The SH had the best performance for silage production based on both total biomass production and biomass quality.