Silage Harvest Preparations

 By Michael Cox for American Cattlemen Magazine

 Corn silage inclusion in beef diets can offer beef producers an economical source of roughage in their ration formulation. Although the cost of corn silage on a dry matter basis is relatively cheap, costs due to waste and shrink can rise rapidly unless good preparations are made for correct storage techniques.

Cleanliness
Providing a clean, dry storage area is a must for successful silage preservation. The silage bunker should be inspected in the weeks before harvest and any necessary repairs made to floors and walls. All old silage and waste should be removed, before the area is lined with a sheet of plastic. If a concrete floor is in place, it may not be necessary to line the floor with plastic, however, lining the sides of bunkers is beneficial as it creates more even silage quality throughout the silo and minimizes wastage along the sides.

Fast filling
Regardless of what type of storage option is used, from bunker to tower to feed bags, the main goal in silage storage is to fill the harvested crop as fast as possible. Fast filling increases anaerobic fermentation and reduces spore levels. By filling and packing fast, producers can decrease the crop’s oxygen content, which will greatly aid in good fermentation and creating a stable feed-stuff. Before harvest begins, take time to plan out the logistics of how trucks and machinery will enter and exit the storage area in an efficient and safe manner. If using a repeat custom harvester, spending some time to review last years harvest and if any improvements can be made will be time well spent.
Silo shape is also an important consideration when filling the bunker. Ideally, we want to achieve a wedge shape silage silo, with an angle of approximately 25 to 30 degrees from floor to highest point. Steeper angles make it more difficult to properly pack the sides of the silo. A long wedge shape will also make it easier and faster to spread fresh loads of silage thinly over a larger surface area, and therefore aid in the packing process too.

Packing
While upright silos use the weight of the silage to ‘self-pack’, and silage bags use special equipment for filling and packing, storing silage in a bunker requires careful packing to avoid air pockets. Driving tractors over the silo after each load has been levelled off or at regular intervals is recommended best practice. Regular packing will give better results, as opposed to trying to pack several feet of fresh silage. If possible, five minutes per ton of fresh-weight of compaction time by driving over the clamp will increase faster fermentation rates and also reduce surface area to be covered by plastic. Having adequate horsepower is also necessary to get good results. As a general rule of thumb, the ‘800 Rule’ indicates that 800 lbs of machinery packing weight is required for every ton of fresh-weight crop. Based on this rule, and on how fast loads are being delivered to the bunker, producers can work out the number of machines needed to efficiently pack the silage based on their weight.
 A target of 45lbs fresh-weight per cubic foot will indicate good packing has been achieved. Producers can measure this target by working out how tall the bunker should be based on the bunker dimensions and tons delivered to the bunker.

Covering
Bunkers should be covered with plastic and/or an oxygen barrier to protect the surface area from oxygen exposure and spoilage. Oxygen barriers are a somewhat new technology that act as an impermeable film to block oxygen entering the silo. Regardless of whether an oxygen barrier is used or not, a layer of polyethylene plastic will be needed as an outer cover over the silage. Plastic should be at least 5mm thick and preferably the outer layer should be white plastic, as it attracts less heat than black plastic.  The cost/benefit of oxygen barriers will depend on a producer’s specific situation, but the standard outer layer of plastic is a must. Failing to cover a bunker can result in up to two feet of wastage on the surface of the clamp. Apart from the unnecessary waste, animal health issues can arise if poorly covered and spoiled silage finds its way into the diet. Depending on the construction of the side walls of the bunker, some producers may benefit from lining the sides of the bunker with plastic also. Once the outer layer of plastic is in place, there are several options available to weigh down the plastic; including sand, muck, ‘silage bags’, tires etc. Regardless of the material used to weigh down the plastic, it is important that all air pockets/air bubbles are removed from underneath the plastic and that the plastic is stretched as tightly as possible. As silage will shrink to some degree during the fermentation process, it is best to go ‘overboard’ with tires or weigh material so that no loss of contact will occur as the silage pile reduces in size over time. Regular checking for any cuts or holes in the plastic can help prevent rainwater and oxygen entering the silo and causing spoilage. As is the case with packing silage, time is also of the essence when it comes to covering the silo. Research from Kansas State University suggests that a 24 hour delay in covering silage versus immediate coverage, can results in 27% greater wastage in the top 18 inches of silage at feed-out.
While harvest time can be a hectic period for many producers, taking time to make adequate preparations in advance can help ease the workload and result in a high quality and successful harvest.