Fall harvest compaction outlook
By David G. Hallauer
Meadowlark District Extension Agent, crops and soils/horticulture
As we approach fall harvest, its likely that yields, machinery, and even some fall tillage are on your mind. And while compaction probably isn't at the forefront of what's going through your head these days, it does deserve some attention.
If our fall harvest yields as well as the summer has treated most of us, it could be a good one. Weather has been damp enough that some soils are still wet and temperatures cool enough that corn isn't quickly drying down. That combination of factors could lead to us getting in to harvest fields just a little bit damp--then making more trips across the field to get it out. What can we do?
Understand soil compaction factors, first. Compaction occurs when soil particles are pressed together and space for air and water is limited. The results: decreased soil permeability, greater potential for moisture/nutrient stress, and reduced exchange of gases within the soil. Moist soils are the most subject to compaction.
According to KSU Soil Management Specialist DeAnn Presley, harvest usually leads to deep compaction related to axle load. This is compaction not reduced by distributing weight across more/larger tires, and is usually too deep to remove with tillage. She notes research showing that axle loads greater than 10 tons per axle can be very destructive. A recent research report from Pennsylvania State University stated that annual compaction from a 10-ton axle load reduced corn yield by 17 percent in 3 out of 4 years on a silt loam.
And while we might not see these effects right away, the first time we get a dry spell, we could see reduced crop root growth and increased stress. How much weight are you throwing out there? A typical 1000 bushel grain cart may weigh upwards of 17 tons/axle. A 12 row combine full of corn--20+ tons/axle.
The solution: as best you can, limit traffic when fields are wet and confine traffic to end rows. The first pass of a wheel causes 70 to 90 percent of total compaction, so prevent unneeded traffic routes as much as possible.
Last week, I noted September's preference for fertilizer applications, but it is also an excellent time to thicken that cool season lawn.
Overseeding can be a little complicated. Start by mowing short, removing clippings to achieve good seed/soil contact. This also means that thatch layers over a quarter inch can be a challenge. If so, additional work may need to be done prior to overseeding.
Soil preparation will include verticutting (solid vertical blades set to cut furrows in the soil) from two different directions. You can also use a slit seeder to cut and seed all in one pass. A core aerator can also work if three or four passes are made to ensure adequate holes for seed to drop in to (aeration can also increase water filtration, decrease compaction, and increase oxygen in the soil). Following soil preparation, apply starter fertilizer as suggested on the bag.
Use a half rate of seed when overseeding. For tall fescue, use three to four pounds per 1,000 square feet broadcast over the prepared area. Water in, then keep a moist seedbed to ensure rapid germination. As seedlings establish, move from frequent, light waterings, to deeper and more infrequent irrigation. Fertilize again 4 to 6 weeks after seeding with a high nitrogen fertilizer.