Forage 101

In response to a previous post about our hay harvest, several readers asked about the practice of wrapping bales in white plastic. Bales that are wrapped in this way are being made into what is called haylage. Here on the farm we put up dry hay with a moisture content of between 10-15%. Making dry hay is pretty straightforward. When the weather map indicates three clear days on the horizon you cut the field and let the tops of the windrows dry down. In the early afternoon of the second day you turn each windrow to allow its bottom face to dry. If everything has gone well, you can begin making bales as soon as the dew dries thoroughly on day three. This sort of crop needs to be very dry indeed or there is a real risk that the stuff will go bad, that mold will grow (and potentially make the sheep ill or cause abortion in gestating ewes), or that the barn will burn down. If there is enough moisture in an improperly cured dry bale, bacteria will grow deep inside of it and one of the many products of bacterial metabolism is heat. If there are enough wet bales stored closely together in a barn with little air circulation, enough heat can be generated to set the bales (and the barn) on fire. Therefore the most important aspect of making dry grass hay is knowing when the crop is ready for the baler, and I leave this determination up to Joanna. She walks the windrows in her bare feet … listens to the crunch beneath her steps and is very much aware of the feel of the hay between her toes … I rely on her judgement, absolutely. In contrast to dry hay, wet hay, to be made into haylage, retains 50-60% of its moisture when bagged. Forage intended to be made into haylage is wrapped in plastic to form an air-tight covering over the bale. Bacteria use up the oxygen in the bale and then make the physiological switch to undergo anaerobic fermentation. Along with a variety of sugars, weak acids are also produced. Eventually the fermentation stops and the bale has essentially been pickled. Wrapped bales can last quite a long time if the covering remains intact – if air is introduced, through a puncture, for example, this will support fungal growth and the bale will spoil quite rapidly. Haylage produced in this way has an appealing smell and cows gobble it up like candy. You may be interested to know that silos are built to achieve the same end. The silo provides an oxygen-free fermentation chamber for the development of silage. Silos are big, expensive to build, and difficult to maintain. Putting individual hay bales into bags is a simpler means to an end. The images below show some friends from down the road wrapping bales of haylage. The bales are mounted onto the wrapper which is driven hydraulically (via input provided by the stationary tractor). Joanna pointed out that the motion of the bale wrapper is exactly like that of the ball winder that she uses to produce balls of yarn from skeins of the same. Once the bale is wrapped it is ejected and added to the growing stack while the next in line is loaded onto the hydraulic lift mechanism. While these two were wrapping bales, a third farmer was in the field a half-mile away producing bales. As Joanna and I drove into town this morning we noticed that the hayfield had been cleared of formed bales; good thing, for we had rain overnight and again this morning. [For those with an interest in photographic technique I will add that the image immediately below was taken at ISO 100, f14, with a 5 second exposure, and at 12:32 PM in very bright conditions. I wanted a slow shutter to allow the blurring of the spinning bale – and this was achieved with a fairly small aperture, low ISO and, most importantly, a nine-stop neutral density filter.]



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