How tall fiber hemp gets mowed

Fiber hemp is cut with a sickle bar or disc mower a few inches above the ground, then left lying in the field so it can ret. A sickle bar works like a long pair of hair clippers: a knife of triangular blades slides back and forth through fixed guards, shearing each stalk. How fast a field gets cut depends on ground speed, cutter width, and how much of the time the mower is actually cutting.

Controls

Labels

Animation speed

Ground speed

Cutter width

About 7 ft (2.1 m) is a common mower width.

Field efficiency

Share of field time spent actually cutting, after turns, wrapping and stops.

Step through it

A crop taller than the tractorFiber hemp is planted thick so it grows tall and thin, often 2 to 4 meters. It is cut once the plants reach full height, before the stalks get woody.
The sickle barA knife of triangular sections slides side to side through fixed guards a few inches above the soil. Each stroke shears the stalks trapped between knife and guard.
Laying the swathCut stalks tip backward and lie on the stubble in an even layer, ready to ret in the field.
Speed and widthA wider cutter and a faster pace both raise capacity in direct proportion. Here, 7 mph with a 12 ft bar more than doubles the default rate.
Losing time to wrappingLong fibers wrap around moving parts, and every stop to clear them lowers field efficiency. Drop it to 65 percent and the hours climb.

The field capacity formula

Farm machinery planners use effective field capacity: acres per hour = speed (mph) x width (ft) x field efficiency / 8.25. The 8.25 converts miles times feet into acres per hour. In metric units it is hectares per hour = speed (km/h) x width (m) x efficiency / 10.

Field efficiency covers everything that is not cutting: turning at headlands, overlapping passes, unclogging and refueling. Extension tables list mowers at roughly 80 to 85 percent, and a published hemp logistics study assumed a 2.1 m mower at 11.2 km/h and 80 percent efficiency. The 100 acre figure here ignores travel between fields.

Try it: set speed to 8 mph and width to 14 ft. Capacity jumps past 10 acres per hour on paper. Then drop efficiency to 60 percent, a realistic number when tall fiber keeps wrapping the knife, and watch a big share of that gain disappear.

Why hemp is hard on mowers

The same long, strong bast fibers that make hemp valuable can wind around shafts and moving parts, which is why stops to clear the cutter eat into field efficiency. Growers cut a few inches above the ground and keep the knife sharp so stalks shear cleanly instead of tearing.

Where Avid uses this

Planning harvest timing and machine hours across fields is the kind of farm decision Avid's precision agriculture AI, VerdantaIQ, is built to support.

Sources

Calculating Farm Machinery Field Capacities (AEN-73)University of Kentucky Cooperative Extension
Techno-Economic Analysis of Hemp Production, Logistics and Processing in the U.S.Biomass (MDPI, open access)
Harvesting Industrial Hemp: General Considerations (MX79)University of Missouri Extension

How to cite this model

Avid Solutions International. (2026, November 11). How tall fiber hemp gets mowed [Interactive 3D model]. Avid Field Lab. https://avidsolutionsintl.com/explore/hemp-fiber-mowing

Last updated November 11, 2026

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