Three types of bale wrappings are used with large round bales – twine, net wrap and plastic wrap.
Twine wrapping
Twine, sisal or poly, is the least costly wrap but takes more bale revolutions to produce wrapped bales than net or plastic.
This extra time often negates cost savings. Although twine used in a round-baler application is less demanding than that for square balers, quality twine of consistent thickness and strength is important in maintaining bale integrity.
For optimum tying performance, twine tube knives must be sharpened periodically to maintain a clean cut-off. Twine knives should be removed and file-sharpened or replaced to ensure no gap against the striker plate.
If difficulty is experienced starting twine feed, excessive twine tension might be at fault, or twine may be tangled, incorrectly routed or very tight in the center of a new ball.
In some slick grasses, adjusting twine arms to come no closer than 4 inches together may help. Another thing to improve twine feed is to complete bales with the windrow at the center of the pickup.
If edge twines are loose, the twine tension may be loose or bale edges may not be adequately filled, resulting in barrel-shaped bales.
Also at fault could be insufficient end wraps or end wraps placed too close to the edge of the bale. If all twines are loose or twine tension is insufficient, barrel-shaped bales will result, causing increased storage losses.
If twine is not being cut, insufficient twine tension or dull twine knives may be the problem, or the bale may be too small.
Net wrap
This is a woven material designed to shed water away from the bale surface while promoting greater airflow. It normally requires only two to three revolutions to wrap a bale.
Storage losses are less than those with twine when the exterior bale density is the same. However, net wrap may reduce leaf loss from the chamber during bale formation compared to twine wrapping.
Net knives must be removed and file-sharpened periodically for best performance. Be sure to install the sharpened knife and comb properly. Install the comb first, followed by the knife with the sharp knife edge installed against the comb.
Difficulty starting net feed may be the result of debris buildup, or it could be that the net tail is too short or not cleanly cut. Excessive net tension could also be the problem.
The net could also be pulling out of the duckbill on insertion if the duckbill is too tight. Incorrect net routing could also cause difficult feeding. Check also to make sure the duckbill is not adjusted in too far, pinching the baffle.
When net is not spreading across the bale, it could be caused by debris buildup in the net path, excessive net tension, or the outer edges of duckbill baffles may be too tight.
The net roll not centered may also be at fault or poor bale shape due to uneven feeding across bale. Check to make sure the spreader rolls are rotating freely. Net too loose on a bale could be due to insufficient net tension or inadequate wraps, causing net to slip.
When the net is not cut, check for a dull or incorrectly adjusted knife. Insufficient net tension could also cause this, as well as knife force or timing being incorrect. Another cause could be that the duckbill baffles are too loose.
If the net is damaged after bale ejection, there could be debris in the duckbill, or the duckbill is too tight so net is torn moving through it.
Sharp edges on spreader rolls or net wrapping on rolls, poor-quality net, or inadequate film or net wraps could also be at fault. Check for sharp edges on the floor roll and on the bale ramp mounting.
Plastic wrap
This is a solid plastic barrier that sheds water completely and provides ultraviolet light protection. Dry matter losses during storage are up to five times less with plastic wrap compared to unwrapped bales on the ground.
However, plastic wrap has a much higher purchase price. Plastic materials are used in several ways to produce round-bale silage:
Individually wrapped bales
These normally have six to eight wraps of plastic for an effective seal against oxygen. The advantage is portability and versatility, but these bales often must be baled at slightly lower moisture to prevent seepage, which allows oxygen penetration.
Polyethylene plastic, 4 to 9 mils in thickness, has become the common bale cover material. New, low-oxygen permeability plastics create barriers that are 18 to 400 times less permeable to oxygen.
Plastic tubes
Some machines allow stuffing several bales in a long plastic tube, sealed at both ends. This method uses only between one-half and two-thirds the plastic of individually wrapped bales.
This can be effective and time-saving because one person can complete the process. One drawback is that more bales may spoil if the bag is torn, punctured or opened for feeding out.
Individual bags
Bags come in various lengths, diameters and thicknesses. A spear device is needed to lift the bale while applying the bag. Then the bale is placed in storage position before tying off.
If possible, bales should be stacked in a cordwood pattern. An additional stack cover of netting or plastic may reduce storage damage. Individual bags do not exclude as much oxygen as individually wrapped bales.
Sheet plastic
Hundreds of bales can be wrapped fast and effectively with minimal use of plastic. Seal the end of the first bale with an “end cover” and start wrapping.
When the last bale is to be put in place, cover it with another “end cover” and finish by wrapping sheet plastic around it for a “tube” of bales. The problem with this type of storage is that bales must be used immediately when cut off the tube, thus limiting salability. FG
Curtis Hoffman is crop packaging products marketing manager with New Holland Agriculture.
