The best way to check if fields are dry enough to work is to take a handful of soil and ball it up in your hand. If it sticks together, it’s too wet. If it falls apart, things are probably OK. Make sure to also take some soil from below the surface, down to a foot deep and try this.
Soil compaction can result in a variety of problems. Uneven emergence and early growth rate variability can result in corn and soybeans displaying what I call a “roller-coaster” condition with uneven plant height in a field, particularly in end rows. Compacted soils have reduced water-holding capacity. Poor root system development may lead to nutrient uptake problems or, if the weather turns dry, drought stress. Particularly with corn, the stability of the plant may become a problem. Even if vertical compaction isn’t an issue, planting when it’s too wet can lead to “smearing” of soil in the furrow and sidewall compaction.
If growing conditions are good, moderate compaction often won’t cause many problems. This was the case last year where, as corn planting continued to be delayed, some farmers chose to plant where a field was 80-90% ready and take their chances in wet areas. I saw quite a few fields where sections exhibited sidewall compaction but the weather stayed wet enough that the root system was able to break through the compacted areas. The only real impact I saw was that these areas were a little more susceptible to stalk rots late in the season but not enough to be a major problem. It’s difficult to get a handle on the precise impact of compaction in a given year.
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Farmers can use several strategies to reduce compaction. Some of these, such as no-till, increasing soil organic matter, using cover crops, and improving drainage are longer term in nature. I’ll focus on what farmers can do, other than waiting for soils to dry, to reduce spring compaction.
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| Corn seedling showing evidence of sidewall compaction |
One way to reduce compaction in field work is to decrease the weight over each individual axle as much as possible. Lowering tire pressure will increase the tire “footprint” and spread vehicle weight out over a larger surface area. Using radial instead of bias-ply tires has the same effect. Dual-axle rather than single-axle equipment can also help.
The use of tracked vehicles also helps spread weight out. The key is to have many rollers as weight is greatest under the rollers supporting the tracks.
It's obvious that reducing the number of tillage passes reduces compaction by having equipment run over a field less. However repeated tillage to the same depth can create a tilled surface layer and a layer of underlying dense till which can result in subsurface compaction. Quite often we see armers using a vertical tillage tool or other "light" tillage to loosen up the upper layer of soil so it dries out and warms more quickly. It accomplishes this but it can also result in a compaction layer a few inches beneath the surface.
The most important item to keep in mind is that while there is an ideal planting date for corn, this is only one piece of the yield puzzle, and far from the most important one. Weather conditions such as temperatures and rainfall are more important. Last year’s corn crop was one of the latest planted in history but Boone County Farmers had very good yields. Doing field work when soil conditions aren’t right or “mudding in” the crop can result in problems which may prevent you from being able to take advantage of favorable conditions during the growing season.
