Sealing time, immediate and 24-h delay, and sealing material, standard plastic (std.) and oxygen barrier (OB) film, was compared using whole-plant corn. The crop was harvested on August 21 and 22, 2013 in the 2-thirds milk line stage, contained 32% DM, and was inoculated at the forage harvester. The forage was ensiled in a drive-over pile, which was 18 m wide x 60 m long × 1.8 m apex height with an east to west orientation. One-half of the forage was harvested the first day, packed with a payloader, and not sealed. On the second day, the remainder of the corn was harvested and packed with a payloader. One-half of each day’s forage surface was sealed with a sheet of std. plastic, and the other half sealed with a sheet of OB film, which was protected from UV light with a sheet of std. plastic. The sealing materials were removed from the south half of the pile after 90 d. Samples were collected at 0 to 15, 15 to 30, and 30 to 45 cm depths from the surface at 3 north to south locations, which were equal distance from the east and west boundaries of each of the 4 sealing treatments. The results are presented for the mean of the 3 sampling depths. The immediate sealed silages had a lower (P < 0.05) pH value than the delay sealed silages. The silage that was delay sealed with std. plastic had higher (P < 0.05) ash and NDF contents and lower (P < 0.05) NDF digestibility than the silage that was delay sealed with OB film and the silages that were sealed immediately with std. plastic or OB film. The OB film was more effective than std. plastic in preventing the entry of oxygen into the surface of the corn silage during the 90-d storage period. Delay sealing increased OM loss in the original top 0 to 45 cm of corn silage by 27.2% compared with immediate sealing (15.64 vs. 12.30%). However, delay sealing with OB film decreased OM loss in the original top 0 to 45 cm of corn silage by 20.6% compared with immediate sealing with std. plastic (12.33 vs. 15.54%).