袋式灌装青贮远优越于窖贮(如需转载,请标明出处)

Katie Weber, College of Ag. Life Sci. Press Service, Univ. of Wis., (608) 262-1461

Farmers can save on initial costs plus up to $10,000 a year, while greatly reducing the risks from falls and silage gas. As anyone who has driven across rural Wisconsin can tell you, tower silos are one of the most prominent features on the landscape. Up to 100 feet high, these domed towers are the traditional method of storing forage to feed livestock during the winter. In recent years, however, huge plastic "sausages" have sprouted throughout farm country. The sausages are bag silos or silage bags, a new way to store feed for livestock. In terms of cost, safety and feed quality, silage bags—long, plastic tubes tightly packed with chopped forage—may be a better choice for farmers, according to one University of Wisconsin-Madison expert.

"For both initial investment and annual costs, silage bags save farmers money—up to $150,000 initially and $10,000 per year for a 220-cow herd—over using tower silos or bunkers," says Gunnar Josefsson, a farmer health and safety expert with the College of Agricultural and Life Sciences. "Farmers can talk to their county extension agent to find out what the savings would be for their farm. And, in addition to saving money, silage bags greatly reduce the danger of falls and exposure to silage gas."

Safety is an important issue when it comes to storing silage. In Wisconsin, an average of three people die each year in accidents from silage handling—about 10 percent of total farm fatalities—and more are injured. The chief causes of injury or death are related to tower silos: falling from high elevations and exposure to gas from fermenting forage. Bags, at about six to nine feet tall, pose little risk of falls. And, although silage in bags still produces toxic gas, the farmer does not need to enter a confined space.

Most Wisconsin farms use tower silos, but bags are becoming increasingly popular: Josefsson estimates that almost half of farmers use bags, even if not on a regular basis. "When farmers expand their operations, bags are often the best choice because the silage bag system can be tailored to any size herd. With bunkers and towers, if you don’t have enough cows to consume the feed at a certain rate, there can be spoilage from contact with the air."

However, a temporary solution often becomes a permanent fixture: bottom-line cost analysis makes it clear that bags are advantageous at any scale of operation. "Farmers have to purchase bags each year, and some of the costs of silos, such as the initial investment, are hidden because they are included in a mortgage." Josefsson explains. "However, bags are not included in property taxes as silos are, and you can always sell your equipment for bagging—but you can’t sell a bunker or tower, and it adds very little to a property’s sale value."

Bagging also offers options for farmers other than purchasing the equipment outright. Some farmers share the equipment with one or more neighbors, while others rent the equipment from a dealer or hire an operator to bag their forage. However, Josefsson says that it is hard to generalize what option is most cost-effective, as it depends on the farmer’s specific circumstances. Another benefit of bagging is that, if the silage is managed well, using bags can improve feed quality and reduce spoilage, Josefsson adds. With towers or bunkers, farmers must use the feed in a certain order. However farmers can access feed in bags from either end, and can mark which sections contain high-quality feed so that it can be given to top-producing cows.

According to Josefsson, one of the problems with using bags is disposing of the plastic afterwards. Some landfills may not accept bulk plastic, or accept it only with an extra charge. One common practice is to burn the used plastic, but burning is illegal and bad for the environment. "Farmers are really looking for an improved way to properly and legally dispose of waste plastic," Josefsson says. Already, one manufacturer plans to begin accepting and recycling used bags later this year, and Josefsson predicts that the industry, under pressure from farmers, will begin absorbing the cost. Another potential solution is for farmers to bale their plastic and store it until it can be transported to a landfill or recycling plant.