A mower-conditioner is an agricultural machine that cuts forage crops such as alfalfa, clover, and grass hay while also preparing the stems to dry faster. Fast drying matters because hay must lose moisture before baling to prevent mold, heating, and nutrient loss. By combining mowing and conditioning in one pass, the machine saves time, fuel, and field labor.
It also helps farmers make better hay during short windows of good weather.
As the tractor pulls the machine forward, standing crop enters the header and is cut by a sickle bar or rotating disc cutters. The cut forage then passes through conditioning rolls or flail tines that crush, crimp, or scuff the stems so water can escape more easily. Finally, shields and deflectors lay the crop into a swath or windrow, controlling how much surface area is exposed to sun and air.
The main physics ideas include energy transfer, friction, rotational motion, airflow, and evaporation.
Key Facts
- Field capacity = cutting width x travel speed x field efficiency / 10 when width is in meters and speed is in km/h.
- Dry matter fraction = 1 - moisture fraction.
- Water to remove = wet mass x initial moisture fraction - final wet mass x final moisture fraction.
- Conditioning increases drying rate by cracking waxy stems and increasing surface area for evaporation.
- Disc cutters use high rotational speed to create cutting force, while sickle bars use a reciprocating blade motion.
- Power needed increases with cutting width, crop density, travel speed, and the resistance of stems to cutting and conditioning.
Vocabulary
- Mower-conditioner
- A farm machine that cuts forage crops and conditions them in one pass to speed drying before baling.
- Conditioning rolls
- Paired rollers that crimp or crush crop stems so moisture can leave the plant more easily.
- Swath
- A broad layer of cut forage spread on the field to dry with a large area exposed to air and sunlight.
- Windrow
- A narrower row of cut forage arranged for drying, raking, or pickup by a baler.
- Forage
- Plant material such as grass, alfalfa, or clover that is grown to feed livestock.
Common Mistakes to Avoid
- Confusing cutting with conditioning is wrong because the cutter separates the plant from the ground, while the conditioner damages the stems to improve moisture loss.
- Assuming a narrower windrow always dries faster is wrong because a dense windrow can trap moisture and reduce airflow through the crop.
- Ignoring field efficiency is wrong because turning, overlap, rough ground, and adjustments reduce the actual area cut per hour.
- Setting conditioning rolls too tight is wrong because over-crushing can cause leaf loss in legumes such as alfalfa, reducing feed quality.
Practice Questions
- 1 A mower-conditioner has a cutting width of 3.0 m, travels at 8.0 km/h, and has a field efficiency of 0.75. What is its field capacity in hectares per hour using field capacity = width x speed x efficiency / 10?
- 2 A farmer cuts 5000 kg of forage at 70% moisture. The hay must reach 20% moisture before baling. Assuming dry matter stays constant, what final wet mass will the hay have?
- 3 Explain why crimping or crushing stems with conditioning rolls can make hay dry faster, but why too much conditioning can reduce the quality of alfalfa hay.