Fine-Tune Your Hay Harvest

May 10, 2010 10:14 AM

When the sun is shining, you better be baling. But before you start cutting hay, take a close look at your mower conditioner, rake and baler. Correct management of the cutting and conditioning process will save you money and drying time this summer, while yielding high-quality forage. 

Start by looking at roller drive chains, belts, gearbox oil levels, CV and/or U-joints on all machines. Also check to make sure all lights are in working order and safety guards are in place.

Perform general maintenance on tractors, such as cleaning radiators, keeping engine air and cab filters clean and properly inflating tires before ever leaving the farm.

Inspect mowers for wear on guards and replace any worn, missing or broken knives.

"Uneven stubble and strips of uncut crop mean knives sections or guards need attention," says University of Wisconsin–Madison Extension biological systems engineer Matthew Digman.

Good condition. Conditioning systems on mowers help forage leaves and stems dry quicker. As crop conditions change, adjustments to the conditioning system will speed dry time and quality. Since stems dry slower than the leaves, stem cracking is the most important factor in drying time and condition.

There are two types of conditioning systems used on mower conditioners—roll and impeller. On impeller conditioners, the hood position above the impeller and the speed of the impeller determine the degree of crop conditioning. Most impeller conditioners have a high-speed setting for grass crops and a slow-speed setting for leafy crops like alfalfa. Moving the crop hood closer to the impeller increases the conditioning level.

For roll-type conditioners, roll clearance and pressure ensure stems are properly cracked.

Visually inspect hay to see if at least 90% of stems are cracked at several locations on the stem.

Measure roll clearance, which should be between 1⁄16" and 3⁄32", says Kevin Shinners, University of Wisconsin–Madison professor of ag biological systems engineering. A piece of aluminum foil run through the rollers can help measure current settings.

When the crop is high-yielding and has thick stems, a 3⁄32" clearance is appropriate, he says. For low-yield cuttings and fine stems, adjust clearance to 1⁄16". If the clearance is less than this range, excess leaf loss and roll wear can occur.

Cutting speed also plays a role. High-yielding crops create a thicker mat of forage moving through the rolls, which requires more pressure to crack the stems. Slower speeds reduce the forage flow and allow stems to crack at a lower pressure. Excessive roll pressure leads to leaf loss.

While many people buy rakes and mergers based on price, Digman says to focus on the type of forage being cut and compatibility with mowers and balers. Balers work more efficiently and use less fuel if they are run near machine capacity, so look for rakes that maximize baler intake.

Inside balers, inspect bale belts for wear. As these belts lose tread, the result is slower bale starts, damaged fasteners and poor tracking.

Bearing and U-joint failures are the foremost causes of breakdowns in rotating machinery. Inspect regularly and replace if needed.

Digman also suggests farmers trade twine for net wrap. "Net wrap is more durable, which more than makes up for the extra cost." BT


Measuring Roll Clearance on Mower-Conditioners

To safely conduct this procedure, you MUST:

  • Shut off the tractor engine
  • On mechanically drivent units: disconnect the mower conditionwer PTO from the tractor PTO
  • On hydraulically driven units: disconnect the mower-conditioner PTO hydraulic pump from the tracto PTO
  • Lower the cutting platform

This procedure can be used to determine the roll clearance on most roll type mower-conditioners. The owner's manual of most mower-conditioners will have the proper clearance and the correct procedure for making this adjustment.

Generally, the roll clearance should be in the range of 1/16 to 3/32 inch. If the clearance is less than this range, excess leaf loss and roll wear can occur. If the clearance is significantly more than this range, the crop will not be conditioned as effectively and slower drying rates can be expected.


  1. Cut three (3) pieces of typical household aluminum foil 18" in length. The foil strips should be at least 12 inches wide.
  2. Using each strip individually, form three separate rolls by wrapping a foil strip around a mandrel of rod, pipe or dowel that is 3/8 inch diameter. Slide the roll off the mandrel taking care not to crush the foil roll.
  3. Place one foil roll in the approximate center of the conditioning rolls and the remaining two foil rolls about 1 foot from each end of the conditioning rolls. The foil rolls should be placed perpendicular to the roll longitudinal axis.
  4. Make sure the cutting platform is fully lowered. This is the only safe way to make this measurement, plus on some mower-conditioners, raising the platform also opens and separates the rolls preventing an accurate measure of the minimum roll clearance.
  5. Turn the rolls by hand until the foil rolls come completely through the rolls.
  6. The rolls will crush the foil rolls and the minimum roll clearance can be determined by using a digital or dial caliper to measure the thickness of the foil roll. A low-cost digital caliper (~$40) can be found at Techni-Tool (Part No. 575GA103, 1-800-832-4866). Take several measurements of the thickness along the length of each foil roll and determine an overall average. The measurement should be taken where the "crimp" or smallest clearance occurs as noted in the above figure.

Source: Kevin Shinners, University of Wisconsin-Madison

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