DENSITY AND LOSSES IN PRESSED BAG SILOS

The objectives of this study were to measure densities and losses in bag silos made at three research farms and to determine potential factors affecting both. The primary bagging machines were a 2.44 m Ag Bag model G6000, a 2.74 m Kelly Ryan model DLX shared by two stations and a rented 2.74 m Ag Bag machine. All loads of forage entering the bags were weighed and sampled. At emptying, all silage removed (both good and spoiled) was weighed and sampled. Across 47 bags, dry matter (DM) density ranged from 160 to 270 kg/m3. At all three farms and across crops, DM density increased linearly with DM concentration except with the Kelly Ryan in corn silage where density was constant. Kernel processing appeared to reduce density in corn silage. The bagging machine, operator, and crop also affected average DM densities. Within bags, density was highly variable. Densities at the top and sides were approximately 40% of densities at the bottom, center of the bag. Losses of DM were measured on 24 bag silos and were highly variable (0 to 40%). However, except for six bags with considerable spoilage loss, total losses averaged 11%. Significant spoilage losses were essentially confined to crops ensiled above 400 g DM/kg. Spoilage was also worse in bags fed out in summer. Gaseous and seepage losses were higher at low DM contents and by feeding out at low rates (200 mm/d). While more research is needed to study bagging machines with different systems of filling, the current study suggests that pressed bag silos can do an excellent job of preserving a crop provided 1) crops are ensiled between 300 and 400 g DM/kg, 2) the bagging machine is set up properly to obtain a smooth bag of high density, 3) feedout rates are a minimum of 30 to 60 cm/d and 4) the farmer routinely monitors for and repairs punctures in the bags.