Brief hay lesson:
The length of the bale is set by the farmer who adjusts the baler to “X” inches. You can have 24" bales or 48" bales or anything inbetween. The farmer typically sets this size to stack neatly in a barn, semi trailer, or to fit properly in an accumulator, grapple, or other bale-gathering device. Length may also be adjusted to account for weight/density. It’s common to set bale length to double or triple the chamber width; ie, 14"x16" would probably be set at 32" or 48", so when stacking bales two-by-two, or three by three, two or three bales wide equals one bale long (I hope that makes sense).
Tension is also set. Tension is the tightness of the bale, how much tension on the strings, and affects how much a bale will weigh. (Lots of tension = heavy bale. Less tension = light bale). Most farmers prefer to bale tightly, as it makes bales easier to stack, easier to pick up, and saves on storage (more tonnage per sq ft). Hay that is baled with sisal string (the natural twine) cannot be as tight as plastic twine-- sisal has a much lower tensile strength and will pop if pulled to tightly (if you’ve ever tied with twine, you already know this…horses break sisal string much easier than plastic twine!). Good farmers will use plastic twine with an appropriate tensile strength for the weight and density of their bales. IF your hay is slightly higher in moisture than ideal when baled, the farmer may intentionally reduce the tension so the bales are a bit looser, allowing more airflow and reducing heating/fermentation/combustion.
Size of flakes: this is less a function of the baler and more a result of the width/size of your windrow (That’s the actual cut forage laying on the ground in lines feeding into the baler). Windrow size is determined by the height and thickness of the forage you’ve just cut, and how your rake is set (wide or narrow). Very thick windrows with LOTS of grass will stuff quickly into the chamber, with each thrust of the plunger packing a flake into the bale. Lots of hay feeding in = very big, thick flakes, perhaps only 7-10 flakes per 36" bale. A thinner windrow will result in less forage feeding into the chamber at a time; the plunger is still pushing at a set rate per minute (a function of the tractor PTO spinning), so it takes more plunges to make up the same 36" bale, meaning 10-15 flakes per 36" bale, and each flake will be much thinner. THIS is why you can’t feed your horses “by flake,” because a flake created from a thick windrow may weigh 6lbs, and a flake from a thin windrow may only weigh 2lbs. (The type of forage matters, too.) However, density also comes into play! A 2" thick flake of alfalfa could weigh as much as a 4" thick flake of bluegrass baled with sisal string. WEIGH YOUR HAY.
Windrow size can very for lots of reasons: first cut is typically thicker, more tons per acre than later cuts, so first-cut hay typically has bigger windrows resulting in bigger flakes. Later cuts in the season will often be less quantity, thinner windrows, finer stems/more leaf, and more/thinner flakes in the bale. The farmer could keep raking the field over and over throwing multiple windrows into one, to make bigger windrows for those later cuts, but it may not be cost/time effective to do so.
Thank you for coming to my hay TED Talk.
*I’ve baled over 10,000+ small squares and perhaps 5,000+ large squares (3x3x8s). My husband has done 300x that. I’ve baled and fed alfalfa, orchardgrass, timothy, brome, rye, and clover (and all mixes thereof). Any of them can be excellent; any of them can be terrible. All have some place in a horse’s proper diet at minimum 2% bodyweight per day.