Preventing, remedying soil compaction problems
With the nice weather we’ve been having, corn and bean harvests are in full swing, and any time heavy equipment is out and about, soil compaction can be an issue.
Soil is a complex structure made up of air, water, mineral particles and organic matter. While organic matter comprises only a small percentage of the overall soil makeup, it’s the only component that can be easily changed and have a major impact on the overall health and performance of the soil.
Organic matter is described as the glue that holds the soil together, improving water retention and structure.
The best illustration of organic matter’s impact would be to picture the black, fluffy humus layer of soil found in a wooded area to that of a shovel full of soil from an access road or heavy traffic area.
Cover crops and no-till are the best way to build organic matter over time, and as they are utilized year after year, they improve structure and protect the soil from compaction by acting like a sponge, absorbing heavy equipment traffic impacts then rebounding.
On the other hand, tilled ground typically has much less organic matter and is easily compacted. This causes a cycle of compact and plow to the point that compaction is moved deep into the soil where only deep tillage can remove the problem.
However, with some proper planning most compaction issues can be remedied quickly and easily, starting with a few simple steps.
• Minimize equipment traffic during less than optimal field conditions. Load penetration can increase up to four inches the wetter the soil with some research showing penetration down two feet with one pass in wet soils.
• When harvesting, vehicles equipped with highway tires should be prohibited from fields entirely, but if this is not possible they should be limited to one or two isolated areas and should never run alongside harvesting equipment while filling. The narrow width and high pressures of these tires can create significant soil structure damage even in the driest of fields.
• On the other hand, high flotation tires are ideal for all heavy equipment. These tires run at very low pressures and distribute the load over a large surface area, greatly reducing their impact.
• Another option is to switch from bias ply tires to radials. Radials tout lower pressures, greater surface area and reduce fuel costs. When comparing a bias ply to a radial some research has shown the bias ply creates almost seven pounds more pressure even though there was only a four pound difference in tire pressures between the two types.
The radial also distributes the load over a 40 percent greater area. Another study by USDA Agricultural Research Service with two radial tires — one filled to 18 PSI the other only 6 PSI — showed the tire with the lower pressure had 25 percent greater pulling power, used 25 percent less fuel and had the least amount of compaction.
Of all the different types of compaction surface compaction, compaction found within the top 2 to 3 inches is probably the most common and the easiest to fix.
• Cover crops would be the ideal remedy. Not only do they heave and break up the soil, but they also provide soil structure as they decompose, reducing compaction in future years.
Plow pans or deep compaction from equipment access areas can be tricky to handle, but cover crops like tillage radishes planted alone or with a small grain will root up to two feet deep and grow to 4 or 5 inches in diameter. These plants winterkill and easily remove deeper issues.
The obvious downside to cover crops is planting timing. Compaction due to grain harvests typically prohibits adequate growth to provide enough benefit.
For example, tillage radishes need to be planted by mid-August to realize their full benefit. If this is the case, tillage is needed to remove ruts but tillage practices should be limited to the least disturbing piece available to reduce soil disturbance.
Vertical tillage tools, aerways and turbo-tills, are usually the instrument as they lightly work the upper 2 to 3 inches of soil.
Following these steps will help keep compaction to a minimum and yields on the increase.
Andy Gaver is a conservationist with the USDA Natural Resources Conservation Service in Butler County.
