Baling hay is the process of cutting, drying, and compressing grass or legume crops into compact bundles for storage and later use as animal feed. The entire goal is to capture the nutrients in living plants at their peak and lock them into a form that stays usable through winter, when fresh pasture isn’t available. It’s a multi-step process that depends heavily on weather, timing, and moisture control.
The Four Steps of Haymaking
Haymaking follows a consistent sequence: mowing, tedding, raking, and baling. Each step serves a specific purpose, and skipping or rushing any of them leads to lower quality feed or outright spoilage.
Mowing is the first step. The crop is cut when the grass is still in its early growth stage, before the seed heads have fully emerged. Waiting too long drops the nutritional value significantly. In alfalfa, for example, protein content falls from around 25% at the bud stage to just 16% at full bloom. The fiber content climbs at the same time, making the hay harder for animals to digest.
Tedding comes next. A tedder is a machine that fluffs and spreads the freshly cut crop across the field so that air and sunlight can reach the undersides. Sun exposure is the single most important factor in drying speed. If the ground is damp, farmers sometimes mow into narrow rows first to let the soil dry before spreading the crop out with the tedder.
Raking happens once the hay is nearly dry. A rake turns the crop one final time, drying the bottom layer, and gathers it into long, narrow rows called windrows. These windrows are the lanes the baler will follow.
Baling is the final and most critical step. The baler picks up the windrows, compresses the hay, and ties it into bales using twine, net wrap, or wire. The timing of this step is where haymaking becomes as much art as science. Bale too early and trapped moisture causes mold and spoilage. Bale too late and the dried leaves shatter and break off, stripping away nutrients. The target moisture content is generally between 15% and 18%.
Round Bales vs. Square Bales
The two main bale shapes serve different purposes. Small square bales are the classic rectangular blocks you see stacked in barns. They’re easy to handle by hand and common on smaller operations. Large square bales are much denser, packing roughly 700 to 1,000 kilograms per cubic meter, and are favored by large-scale operations that need maximum storage efficiency.
Round bales are lighter and less dense, holding about 500 to 700 kilograms per cubic meter. That lower density is actually useful: the looser structure allows air circulation, which helps pre-dried hay continue to cure after baling. Round bales also shed rain better than square bales when stored outdoors, making them a practical choice for farms without covered storage. Their cylindrical shape means water runs off the sides rather than pooling on a flat top.
Why Moisture Levels Matter So Much
Getting the moisture right is the difference between quality feed and a ruined crop, or even a barn fire. The safe thresholds vary by bale type: small square bales should be at 20% moisture or less, large round bales at 18% or less, and large square bales at 16% or less. Larger, denser bales need to be drier because heat has fewer pathways to escape from the center.
When hay is baled too wet, plant cells and microbes continue to respire inside the bale, generating heat. A small amount of heating, up to about 130°F, actually helps by evaporating residual moisture. But above 158°F, chemical reactions take over and the temperature can climb on its own. At 175°F, you should call the fire department. At 212°F, ignition is almost certain. The combustion point of hay is between 448°F and 527°F, and a wet bale can reach those temperatures internally without any external spark. This is called spontaneous combustion, and it burns down barns every year.
Acid-based preservatives can help when weather forces farmers to bale at higher moisture levels than ideal. These products reduce heating but don’t eliminate it, and their effectiveness drops off sharply once bale moisture exceeds about 25%. They’re a safety net, not a replacement for proper drying.
How Weather Controls the Timeline
Farmers typically wait for a stretch of clear, dry weather before cutting. Once the crop is on the ground, it needs two to four days of good conditions to dry, depending on humidity, wind, and sun. Overcast, humid weather can stall the drying process entirely. Rain on cut hay is especially damaging because it leaches nutrients and restarts the moisture clock.
This weather dependency is why haymaking is often stressful. A forecast that shifts unexpectedly can leave hundreds of acres of cut hay sitting in the rain. Tedding helps speed things up, but there’s no real substitute for sunshine. Chemical drying agents exist, but they only work well under already favorable conditions.
Alfalfa Hay vs. Grass Hay
The two broadest categories of hay are legume hay (primarily alfalfa) and grass hay (timothy, orchard grass, meadow mixes). Alfalfa consistently delivers more protein, with typical values around 127 to 139 grams of crude protein per kilogram of dry matter. Grass hay runs significantly lower, around 79 to 88 grams per kilogram. Energy content between the two is roughly similar, so the main advantage of alfalfa is its protein density.
This difference matters for feeding. Alfalfa is often chosen for dairy cows, young growing animals, and horses with high energy demands. Grass hay suits animals with lower protein needs, like mature horses at light work. Many farmers grow both or buy a mix depending on what their livestock require.
Storing Hay Without Losing Quality
Even properly baled hay loses nutritional value in storage, and how much depends on the wrapping method and whether the bales are kept indoors or out. Twine-wrapped bales stored outside lose the most dry matter. Net wrap performs better, shedding water more effectively and holding the bale’s shape. Plastic wrap or sleeves give the best protection, limiting dry matter loss to about 5 to 8% in the first year and an additional 2 to 5% in the second year.
Indoor storage in a barn or shed remains the gold standard. Bales kept off the ground on pallets or gravel, under a roof, with good airflow will retain the most nutrients. For farms that must store outside, net wrap and positioning bales in rows oriented north to south (maximizing sun exposure on the sides) helps minimize losses. Bales should never sit directly on bare soil, where they wick moisture from the ground.