Cover Crops Better for Reducing Soil Compaction Than Additional Tillage

    Because it happens out of sight, soil compaction is a problem that can be hard to recognize and even harder to fix, but it takes a financial toll when ignored.

    Compacted soil has a dense layer somewhere below the surface where individual soil particles are pressed together more tightly than normal. In many cases, roots are unable to penetrate the compacted layer of soil, limiting plants’ access to moisture and nutrients.

    Ernie Flint, a regional agronomist with the Mississippi State University Extension Service, said soil compaction is an extremely important issue in farmland.

    “I find that many growers assume that compaction exists, and they often do excessive and destructive tillage that makes soil more prone to breakdown and erosion,” Flint said. “There are simple tests for compaction, but few growers use them. Instead, they spend millions of dollars in labor, equipment, fuel and time performing deep tillage on soil that may not be needed.”

    Larry Oldham, Extension soil specialist, said one way to prevent soil compaction is to eliminate unnecessary tillage.

    “Sometimes there is an overreliance on tillage, but there are instances where it is unnecessary to till,” Oldham said. “Sometimes it’s OK to harvest and go in later and plant without tillage.”

    A compaction problem can result from poorly timed tillage, such as working the soil when it is too wet.

    “This puts too much downward pressure on the soil, compressing it well beyond its normal density,” Oldham said. “Well-aerated soil is necessary for soil quality and health. Compaction is the opposite of well-aerated.”

    Performing tillage at the proper times can limit soil compaction, but Flint said another component to consider is that of traffic patterns in fields.

    “When the grower restricts equipment traffic to the same paths or rows, only these strips are compacted, which is much better than compacting many different sets of tracks as is the case when implements like disks or field cultivators are used,” Flint said. “A consistent traffic pattern limits compaction into a very small portion of the field.”

    Billy Kingery, an agronomist working in soil science with the Mississippi Agricultural and Forestry Experiment Station, said prevention is the best way to address the problem of soil compaction.

    “As much as is possible, reduce tillage and use cover crops in the winter,” Kingery said. “Many producers think of cover crops as cash crops, which can be true, but in this case, we’re talking about using several species mixed together, which along with crop residues, will provide both the organic matter and the complex food sources needed to increase the number of microorganisms in the soil.

    “But we cannot forget pest control in these systems. Cover crops must be carefully selected and managed so they do not themselves become part of the pest problem. When managed carefully, you can get enough accumulation of carbon over the growing season and offseason to help the soil regenerate and maintain itself,” he said.

    These practices have the added benefit of reducing costly inputs, and many farmers are already skillful at taking these steps to maintain and improve the soil.

    While prevention is best, much of the state’s farmland already has problems with soil compaction. Undoing the damage caused by soil compaction is a lengthy and often extensive process.

    When producers are confronted with compaction caused by their equipment, their first response is often to attempt to fix the problem with another implement, Flint said.

    “You can reduce compaction with a chisel plow or one of the various subsoilers that fracture the deep layers of the soil,” Flint said. “However, a preferred way to reduce the soil’s proneness to compaction is to increase soil organic matter so that it has the ability to repair itself through the activity of earthworms and deep-rooted cover crops.”

    Soil that has been tilled too much requires more tilling annually to make it useable as cropland. Flint said it is almost as if the soil is addicted to tillage. Breaking that cycle is painful.

    “To break the tillage habit, you have to stop doing unnecessary tillage. Plant corn, grain sorghum or a winter grain, then restrict traffic patterns and apply organic materials such as poultry litter. Keep the soil covered with growing plants to reduce erosion and create root channels,” Flint said. “The next spring when the cover crops die, the soil is more open to take in water and air needed by crops. It sometimes takes two to three years for soil to get back to a normal state that will perform well in the production of summer crops.”

    Tillage will always have a place in agriculture, but reduced-tillage farming methods offer many benefits. Most of these benefits produce profits when done correctly.

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