By the time hay is baled, a great deal of resources (land, labor, seed, fuel, fertilizer, equipment) have gone into the production of each bale. The way that hay is stored after baling can have a large impact on losses in hay quantity and quality, so it is worth investing additional resources (money, labor, equipment) into hay storage to preserve the value of the hay and to ensure a good return on the initial investment.
Molds and bacteria that consume nutrients contained in hay cause most of the dry matter and quality losses that occur during storage. Molds and bacteria grow and reproduce faster if the hay is warm and moist, and of course, the more time they have to work, the more damage they can do. This means losses are lowest if hay is kept cool and dry and stored for as short a time as possible.
Livestock feeders and hay processors often need to store hay for year-round use, so their primary option for reducing storage time is to make sure that the first hay harvested is the first hay fed. They have little ability to control hay storage temperature, since most hay is stored outdoors or in buildings that have no environmental control. Thus, controlling moisture is probably the best strategy for limiting hay storage losses. This includes baling at a moisture that is low enough to prevent mold activity and then using storage methods that protect the hay from being rewet by precipitation or soil moisture.
Timing of baling is critical for maximizing the value of hay. Optimum moisture for baling is in the range of 15 to 20% moisture (wet basis). Baling at moistures lower than 15% will result in greater harvesting losses, especially for alfalfa, where leaf loss increases as moisture decreases. Storing hay at moistures greater than 20% will result in some molding and heating, greater dry matter and nutrient loss during storage, and some discoloration. Large hay packages, especially large rectangular bales, do not lose much moisture after baling, so it is important to bale at the proper moisture rather than baling at a higher moisture and counting on some natural drying in storage.
When storing dry hay outside, it is worth considering methods to prevent direct contact between the ground and the bottom layer of bales, because the bales resting on the ground will absorb enough moisture to support mold growth. Research studies and farmer experience have shown that placing hay bales on layers of coarse gravel, old tires, or wood pallets has been effective for preventing rewetting of hay by soil moisture.
A hay storage study was conducted at the University of Minnesota West Central Experiment Station at Morris Minnesota* to determine losses that can be expected for different storage methods, under Minnesota conditions. Hay for the study was third cutting alfalfa baled at about 18% moisture in September 1996. Half of the hay was baled as 5-ft diameter by 6-ft long large round bales and the other half was baled as 3-ft by 4-ft by 8-ft large rectangular bales. Bales were stored until mid-June 1997 (about eight months) and then re-weighed, re-sampled, and sold. Storage methods included:
Round bales were stored on their sides, pyramid style, in piles of twelve bales. The bottom layer was three bales wide by two bales long, the middle layer two by two, and the top layer one bale wide by two bales long. The rectangular bales were stored in piles of eleven bales, all oriented the same direction, and resting on their four-foot wide sides. Nine of the rectangular bales were stacked three wide and three high, and the top two bales were placed over the cracks between bales in the lower layers.
We found that for both round bales and rectangular bales, the bottom bales in piles that were stored uncovered, on sod, rewet from their initial moisture content of 18% to a final moisture of about 32%-high enough to cause significant spoilage by mid-June. Spoilage would have been even worse if bales had been left in place through the summer. The percentage of the total volume of bottom bales that appeared to be spoiled was about the same (22 to 23%) for both round and rectangular bales. This compared to 1 to 8% of the volume spoiled for bottom bales stored on gravel or in the barn. Water from rain and melted snow can also rewet hay to moisture levels that are high enough to support mold growth. In our study, the advantage for covers was about six percentage units; average dry matter loss for bales stored covered on gravel was 4.8%, compared to 10.9% for bales stored uncovered on gravel.
In the treatment where bales were stored uncovered on sod, the upper layers of round bales did not show any increase in moisture and the upper layers of rectangular bales rewet slightly to an average of about 22% moisture. Even though the average moisture absorption in the upper layers was relatively small, the "water-shed" locations (points where water ran off on upper bale onto a lower one) showed greater moisture increases and very obvious mold development, particularly in the large rectangular bales. Average dry matter losses in the uncovered piles on sod were 11.2% vs. 2.3% in the barn.
Besides losing dry matter, uncovered hay also loses quality as determined by nutritional analysis and appearance. The loss in dry matter reduces weight available for sale and the loss in quality can have a large impact on animal performance and price. For example, in our study at Morris, hay stored in the barn sold for $75 per ton, while hay stored uncovered on sod lost about 10% more dry matter, and it sold for only $45 per ton. Thus, quality and quantity differences made the hay stored in the barn worth about $3350 more for each 100 tons harvested. These numbers indicate that it is worth investigating the cost of buying tarps and gravel, or even erecting a storage building for hay storage.
At this point, there doesn't seem to be a clear overall advantage for one bale type over the other. Advantages of large round bales include greater availability of balers and handling equipment (at this time), lower price for balers, and greater ability to shed water if bales are stored uncovered. Disadvantages include less efficient use of space in hauling and storing bales, and tendency for bales to lose their shape during storage. Advantages of large rectangular bales include more efficient use of space in transport and storage, and better shape retention during storage. Disadvantages include greater cost and lower availability (at this time) of balers, and greater moisture absorption by bales stored without cover. In spite of the tendency for uncovered large rectangular bales to absorb more moisture than large round bales, our study at Morris indicated no significant difference in average dry matter loss for the two bale types over an eight-month storage period.
To get the greatest value from dry baled hay:
*The Minnesota Valley Alfalfa Producers and the University of Minnesota are conducting a comprehensive cost-shared research and development program in support of the Minnesota Agri-Power project. The Minnesota Agri-Power project is supported by Minnesota Valley Alfalfa Producers, Minnesota farmers, U.S. Departments of Energy and Agriculture, University of Minnesota, Oak Ridge National Laboratory, National Renewable Energy Laboratory, Minnesota Department of Agriculture, Legislative Commission on Minnesota Resources, Agricultural Utilization Research Institute, Minnesota Forage and Grassland Council, and others.
This page is part of the Biosystems and Agricultural Engineering Department web at http://www.bae.umn.edu/