Spontaneous Combustion
O ur valley’s hot summer months regularly do their job on the green fields of alfalfa. Irrigation water keeps the plants growing until they’re one to two feet high, lush and leafy. The mower then cuts the entire field, laying the new mowed plants in long rows, called windrows. The memorable fragrance of freshly cut alfalfa is worth rolling down the windows when driving through our valley farmland.
After an appropriate drying period, when the moisture content of the cut alfalfa is correct, a baler travels up and down the windrows, packing it into bales. Most farmers in this area produce the 100-pound rectangular bales. In other farming areas they produce much larger rectangular ones, and even a very large round version. Since my experience with hay is limited to the smaller bales, all references are to the 95125 pound variety.
The bales are collected out of the field using a machine designed to pick the bales off the ground, position them into eight-bale layers, then arrange them into eight-layer stacks. These 64-bale stacks are carried to the roadside for easier access, often being placed together in rows of several stacks. This process is repeated several times during the summer for as soon as the bales are off the ground, the field is irrigated and the plants regrow.
Producing high quality alfalfa hay is not as simple as: irrigate, mow, bale, stack, then irrigate again. Recentlycut alfalfa has to dry the proper time before baling occurs. This leaves it with sufficient moisture to produce the highest value hay, and dry enough to prevent spontaneous combustion. The stalks and leaves must retain enough moisture to be baled without having too many of the nutritious leaves knocked loose during baling. Much of the nutritive value of the alfalfa plant will be lost if too many of the leaves are knocked off. Careful timing in the drying phase, combined with reasonable handling of the long rows of cut alfalfa, will produce bales of leafy hay just right for feeding our animals.
Hay termed as “stemmy” is mostly stems with not much leaf, and is of lesser quality than hay retaining most of the leaves. However, in all fairness, even “stemmy” hay has feed value.
At this point, if it has been baled too quickly, the leaves and stalks haven’t dried sufficiently to prevent dangerous heating. Any bales approximately 15% moisture content will produce a small amount of heat during the continual drying process, then cool after a drying period.
However those over approximately 22% moisture, termed wet bales, can start a chemical process which causes dangerous heating. Not only does the nutritive value of the hay rapidly decline with the heat, the continuing increase in temperature creates the real possibility of the whole stack going up in flames.
The respiration of the plant fibers, which is actually the burning of plant sugars to produce energy, releases a small amount of heat. The respiration of properly dried hay, that of 15% moisture or less, will slow and eventually end with a minimum of heating.
Bales exceeding 2025% moisture have a much greater potential to heat to dangerous levels because of the growth of the mesophilic bacteria, found in all forage crops. This bacterial growth can create temperatures of 130 to 150 degrees. This encourages the growth of heat-loving thermophilic bacteria. When they multiply, additional heat is produced, and can raise the bale temperature to dangerous levels.
The University of Montana published an article saying any hay with internal temperature of 150 degrees is in the danger zone and should be monitored on a daily basis. At 160 degrees, the hay temperature should be monitored every four hours. At 175 degrees, they suggest calling the fire department, for spontaneous combustion is a serious potential. Hay that warm, stored inside a barn, should be quickly removed and separated from other hay. The hot stack should be dismantled carefully. At 185 degrees, when the hay is exposed to the air, flames are almost certain to develop because of the production of flammable gasses
Because the heat source is a chemical reaction, often deep inside the stack, a dangerous pocket of slowly burning hay may exist. Walking on top of a “hot stack” can be perilous. The person’s weight can cause the unburned top layer to collapse into the burning pocket. The resulting injuries could be disastrous.
Modern baling machines bind the bales into tight bundles using three strands of synthetic cord. In years past, the balers used iron wire to hold the hay together. The folded wire bundles provided material for countless repair projects around the barn, in a myriad of spots on any ranch, and all over a multitude of mechanical devices. It even provided a ready supply of light welding rod for an oxy-acetylene torch.
During a busy winter of feeding hay, a stack of baling wire accumulated in a corner somewhere. In the spring farmers were often approached by someone willing to haul it off to the metal dealers, thus recycling the product. Today, the synthetic orange cords are only good for throwing away at the dump adding to the other slowly deteriorating synthetic products.
I dislike the appearance of orange baling cord holding something together. It has a tacky, even shoddy appearance. It looks as if you should’ve fixed it right in the first place. However, the same part, well secured by a couple of tight strands of baling wire, looks entirely practical, maybe even thrifty. Sometimes it’s so good it becomes a permanent repair.
If you need some baling wire, go to Weisenberger’s Hardware. They sell it in small rolls. While you’re there, thank them for sponsoring this column. Brent Gill lives in Springville. His “Daunt to Dillonwood” column appears regularly in The Porterville Recorder through the generosity of Weisenberger’s Hardware on West Olive in Porterville. If you enjoyed this column, follow his blog at http://brentgwriter.blogspot.com.