Oct 16, 2019Repairing last season’s ruts and compacted soils
Vegetables were “mudded in” across Michigan this spring. Fields now need special care to repair ruts and break up compaction.
Many words have been written about the prolonged wet weather in the spring and early summer of 2019. The effects of this spring will be felt long after this year is in the books, especially in terms of soil health. With transplants on hold and maturity windows closing, vegetable growers across Michigan were faced with tough decisions and less than ideal planting conditions. This led to vegetable plantings being “mudded in,” resulting in field ruts and widespread compaction. These ruts need to be leveled before next year’s growing season, and this fall provides a window for field leveling and care.
The goal in repairing these ruts is to break up compaction and level the ground, as well as prevent further erosion and damage. Compaction decreases water penetration, halts root growth and reduces yield. Depending on what is being rotated into damaged areas next year, leveling will be necessary to adjust plant spacing and lay plastic.
The first step is figuring out the depth of the compaction layer. The depth of this layer will vary across the field – it will be deepest in areas where heavy equipment drove over wet soils, making deep ruts. In areas with less traffic, the compaction layer may be much shallower. A technique for locating your compaction layer is using a soil penetrometer. This tool is a cone-tipped rod attached to a gauge. It measures the soil’s resistance to penetration, similar to what a plant’s roots experience. The gauge will indicate green, yellow or red as a representation of what’s going on in the soil profile. There is no critical level when using the tool, but the colors are a good indicator of the degree of compaction. If you don’t have access to a penetrometer, you can use a tile probe or soil probe to get a rough idea of how deep compaction is in the soil profile.
You don’t want to till any deeper than needed, so knowing the depth of your compaction layer is key. Once you’ve found it, set your tillage depth just slightly below the depth of your compaction layer.
Different tools are better suited to breaking up compaction at different depths. When trying to level deeper field ruts (5-10 inches), primary tillage tools such as chisel plows may be needed. If your compaction layer is 2 to 4 inches deep, use a secondary tillage tool. These tools could include field finishers or vertical tillage tools.
When compaction problems are severe and the compaction layer is below primary tillage depth, consider subsoiling or deep tillage (tillage deeper than 10 inches). Subsoiling should be done when soils are not saturated; if soils are too wet, the necessary shattering will not occur and deeper soil compaction could occur. Subsoiling in the fall with a low disturbance tillage tool can break up compaction layers 12-18 inches deep, allowing better water movement and aeration. The freezing and thawing of Michigan winters help settle the soil surface prior to spring planting.
Once you know how deep to set your equipment, wait until the conditions are right. The ruts are there in the first place because of heavy equipment running over wet soils, so we don’t want to repeat this while trying to undo the damage caused this spring. This season has been one of long periods of waiting, and for this tillage to be effective, more waiting may be needed for dry soil conditions. In an ideal world, we would only do tillage in the summer when soils are dry, which helps shatter the compaction layer and creates fewer problems in the future. In reality, most tillage is done in the fall after harvest.
Use an appropriate tool set at the right depth for the compaction layer you’ve measured, and in some cases, multiple tools working at multiple levels may be needed. Follow with a cover crop.
Covers crops are important because they help improve overall soil health, which can help fields be ready sooner the next time a wet spring rolls around. Cover cropping can improve water infiltration by improving the soil structure. The organic matter cover crops provide over time also increases water-holding capacity. While repairing ruts is a short-term goal, the cover crop you plant afterwards can help your fields fare better in the next wet year. For a better idea of what might work with your planting window and crops, play around with the Midwest Cover Crop Council’s Cover Crop Decision Tool.
Above, Wet soils and limited planting windows led to field ruts and compacted soils. Photo by Marissa Schuh, MSU Extension.