This item was written by Bruce Anderson, extension forage specialist, University of Nebraska.
If you expect to harvest alfalfa soon, be careful to minimize wheel traffic on wet soils. This spring's soggy season - which for some seems to be going on forever - calls for caution.
Every time you harvest a field of alfalfa, swathers, rakes, tractors, balers, and other equipment drive over nearly every plant one or more times. During an entire year, some plants are driven on more than 10 times.
All this traffic has to cause some damage, but how much? Studies have shown when fields are dry, plants driven on within one day of cutting and before regrowth occurs will yield about 5-7% less at next cutting.
However, driving on these plants just seven days after cutting, when regrowth shoots have started to grow, reduces yield over 25%. Survival of these plants is also reduced.
Driving over the same plants a second or third time the same day caused about the same change in survival or yield as driving over them just once. However, when fields are wet, wheel traffic causes much more compaction. When this happens, yield loss typically exceeds 30%.
These studies emphasize the benefits of baling and removing bales from hay fields as quickly as possible after cutting as well as minimizing driving on wet soils.
They also suggest adjusting equipment so more wheels trail one another, or following the same trail when removing bales or stacks from fields to reduce damage from wheel tracks. Controlling traffic, which has been studied, can help you confine compaction, and reduce yield loss. But it takes planning and may require some wheel width changes for equipment.
Alfalfa fields must be driven on during harvest but you can lessen damage by controlling where, when and how often you make those trips.