You can have healthier soil that holds more water by following a three-step approach
If the concept of soil health is vague, here’s how it applies to your farm: In healthy soil, water infiltrates rather than runs off. Healthy soil can store more water and release it to your crops.
Healthy soil contains more usable water because the water is stored with oxygen in macropores where roots can reach it. (In contrast, unusable water is stored so tightly, in tiny spaces, that roots can’t get to it.)
If your soil is sick, there are ways to nurse it back to health. How long it takes depends on how unhealthy your soil has become. “It’s worth the effort because healthier soil means more water for crops, which leads to higher yields,” explains Farm Journal Field Agronomist Ken Ferrie.
To get your soil back on track, follow these three steps to restore health:
1. Get water into the soil
2. Create conditions for water storage and root growth
3. Manage the high water table
You’ve probably noticed, perhaps on land you farm, after a hard rain, water ponds in the low areas of one field, but not in the field across the road, even though they have similar soils and topography.
You think to yourself, “That ponded area needs tile. Or, maybe, deep ripping to break up dense, compacted layers.” Maybe it needs both, and maybe it needs neither. Maybe the whole field needs treatment.
“The problem is getting water to infiltrate into the soil—not just in the low areas but on the higher topography too,” Ferrie explains. “If the rain had infiltrated the higher areas—as it should have—it wouldn’t have run off into the low spots.”
To improve infiltration, prevent the surface from sealing. “Never under-estimate the damaging power of a big rain,” Ferrie says. “It breaks down soil structure, which causes the surface to crust and seal. The first hard driving rainstorm of the spring can seal the soil surface for all the rains to come.”
The solution is to keep the soil surface covered rather than bare, Ferrie continues. “No-till is a good solution, but not everyone feels they can no-till, perhaps because of disease concerns, continuous corn or their soil is too sick to be no-tilled until they take other corrective measures,” he adds.
If you must do fall tillage, Ferrie advises modifying practices to leave enough residue to protect the soil from heavy rains. Change the amount of surface residue by using different shanks on your tillage tool or changing their spacing. Ask yourself how black you really need to leave that field.
Residue management is not just one practice—it’s a system. “When you leave more residue on the surface, you must be able to plant through it,” Ferrie says. “That will require residue managers on your planter, properly adjusted for each field’s conditions.”
You can still achieve picket fence stands and photocopy plants if you leave cover to protect the soil—but you might have to change your view of what constitutes a perfect seedbed, Ferrie warns. If you continue to plant into bare soil, you will pay a price all season long with runoff from higher areas and ponding on lower ground.
Cover crops can help, but, like anything else, they require management. Your first objective is to find a cover crop that replaces the surface cover you removed with tillage, Ferrie adds. Once you find one that will grow in your area, you can think about what other benefits cover crops might provide, such as nitrogen production or deep rooting to break up dense layers.
After you protect the soil surface, the next step toward better infiltration is to improve aggregate stability, creating a healthy crumb-like structure, in the top 6". This kind of structure provides macropores to store water and oxygen—60% water and 40% air is ideal for root growth. “Improving aggregate stability primarily involves planting grass crops—either cash crops such as corn, wheat and barley, or grass cover crops,” Ferrie says.
“As you work grasses into your rotation, try to maintain the soil’s biochannels, which allow water to move into and through the soil. Biochannels are created by nightcrawlers and earthworms, as well as crop roots.
“Tillage reduces biochannels,” Ferrie continues. “So to improve this aspect of soil health, you must transition to reduced tillage, strip-till or no-till. There is simply no way to do tillage without degrading aggregate stability.”
If you want to maintain biochannels and continue doing tillage, plant a cover crop that helps create channels, such as radishes.
Some soils, such as sand, silt or clay, hold more water because of texture differences, Ferrie notes. You can’t change a soil’s texture, but in most soils, biochannels can be improved.
When it comes to managing soil health, every field has different requirements. “You have more leeway to do tillage in soils with high organic matter content, good aggregate stability and grasses in your rotation,” Ferrie says. “When a farmer is used to farming soil like that, and then applies the same practices to a more fragile soil, train wrecks can happen. You can create a problem in three or four years that will take 10 to 15 years to fix.”
Having your soil’s aggregate stability evaluated by a lab can provide a benchmark to measure progress. Or, you can do your own aggregate stability testing in the field. The Cornell University Soil Health website (http://soilhealth.cals.cornell.edu) will tell you about both.
It might not be the solution to every ponding problem, but drainage is an important component of soil health. If soil macropores contain 100% water and no oxygen, neither plant roots or aerobic soil microorganisms can flourish. The critical role of drainage in soil health is to manage the seasonal water table.
Drainage is an important part of soil health because it manages the seasonal high water table—letting oxygen enter the soil for plant roots and soil microbes. But it often takes more than drainage to restore unhealthy soil.
“You need to prevent the seasonal water table from getting high enough to take out root systems (from lack of oxygen),” Ferrie says. This is achieved by the depth and spacing of tile lines, as well as outlet capacities.
“Once tile is in place, make sure water can move freely, both upward and downward, without compaction from wheel tracks or tillage layers,” Ferrie says. “You may have to use deep tillage to remove dense or compacted layers to improve soil health and the volume of usable water.”
In some fields, drainage might be the first step to improve soil health. “Wet soil can lead to a downward spiral for soil health,” Ferrie says. “If you have to till to dry out a field to plant, you destroy surface structure, aggregate stability and create compaction.”
In a field like that, install drainage, Ferrie says. “Follow with vertical tillage to remove compacted layers,” he adds. “Then, reduce tillage and add grass cash crops or covers. But in this case, the damage to the soil has already been done, and it may take 15 or more years to restore that soil’s health.”
No two fields are the same. “You must assess each one from the top down,” Ferrie says. “Get water in (surface structure); move it down (aggregate stability); increase usable water (macropores); manage the seasonal water table (drainage); and eliminate compaction and dense layers for the movement of roots (vertical tillage).
“Some fields may need only one or two practices to restore water infiltration and movement,” Ferrie says. “Others may require a long-term commitment to reducing tillage and adding cover crops. If you farm soil that’s already in good health, do everything you can to keep it that way.”
Radishes Improve Infiltration in Tilled Soil
In a study by Ken Ferrie, planting a cover crop of tillage radishes following fall tillage dramatically improved water infiltration. When the radishes decompose, they leave biochannels that carry water downward. “Where the disk was used, the water still had to deal with a disk layer at 4",” Ferrie says. “But at least it was able to infiltrate rather
Building on the Systems Approach, the Soil Health series will detail the chemical, physical and biological components of soil and how to give your crop a fighting chance.