There are several methods for mechanically desiccating vines. They each have some advantages but their problems usually outweigh them. One problem that they all have in common is that the vines are removed and death is too quick. A too rapid vine death causes tuber problems such as vascular discoloration.
Beating and Flailing
A vine beater consists of a drum with either chains or flails attached that are hanging down and, while the drum spins, shred the vines. It works best when the lengths vary according to the contours of the rows. Beating and flailing works best when done in combination with chemical vine desiccation, either just before or a week after application.
Advantages -- It is quick and easy, and there are no debris piles.
Problems -- The chains can remove some of the soil, and can hit exposed tubers skinning them. The terrain can affect efficiency. Maintenance can be difficult.
A roller consists of a bar with used tires from end to end and dragged behind a tractor. It rolls over vines crushing them.
Advantages -- It is cheap. The field gets smoothed and works well with chemical desiccation.
Problems -- It has one very big problem. By crushing vines, the tires pick up sap from the stems. If the plant is infected, whether it is a virus such as leaf roll, bacterium such as black leg, or fungus such as late blight, the sap on the tires will spread the pathogens (disease-causing agents) throughout the field causing major problems in storage and with the next year's crop. Also, rolling is relatively ineffective as a desiccation method by itself.
Undercutting involves dragging a metal blade through the row cutting the vine just below the ground. This is an old method, still used in dry bean harvest.
Advantages -- It is cheat and there are few clods produced.
Problems -- The big problem is that if damages tubers near the surface reducing yield and quality. Desiccation may be partial and regrowth of branches is common.
Special equipment is used for pulling with which vines are physically pulled out of the ground.
Advantages -- Desiccation begins immediately and complete. Pulling is done easily with the proper equipment. The risk of spreading disease spread is nearly eliminated.
Problems -- The equipment is expensive and is not readily available everywhere. Soil dries as well as the plant possibly causing harvest problems.
A flamer is pulled behind a tractor. It carries propane gas which is ignited at the nozzle and literally cooks the vines. The tractor must travel relatively fast to avoid danger to the equipment and operator.
Advantages -- It is fast.
Problems -- It is dangerous and scarry.
Vine beater chains and flails: