How to Manage Sand and Repair Soil on Flooded Fields
Nearly 150,000 growers and over 16 million corn, soybean, and wheat acres were affected by the mid-March flooding in Nebraska, Iowa, Missouri, and Kansas. In addition to road closures, split grain bins, displaced families, lost livestock, and other major impacts, the condition of cropland is top of mind.
If you’re one of the farmers whose fields were covered with floodwaters, you may be fighting deep sand deposits, which create many challenges in preparing or repairing the soil for planting.
Guidelines for Repair
According to Mahdi Al-Kaisi, professor of agronomy and Extension soil and water specialist at Iowa State University, you can till sand into the soil, remove sand, or abandon a field depending on the depth of accumulation.
- Sand a few inches (i.e., 2 to 4 inches deep) can be incorporated in soil using normal field operations. Otherwise, minimum soil disturbance is advisable.
- If sand is up to 6 inches deep, then moldboard plow to a depth twice the sand depth to incorporate.
- If sand is 8 to 24 inches deep, it is advisable to consider spreading it to areas with less sand and incorporate with special deep-tillage equipment. It is not advisable to move sand to fill lower or several eroded areas in the field without proper topsoil to cover the sand.
- For sand more than 24 inches deep, evaluate the cost of removing or stockpiling sand.
- In the case of severe erosion and deep cuts, topsoil from surrounding fields should be used to fill such areas.
Tilling and Removing Sand
If you are able to till the sand into the soil, you’ll want to ensure it’s thoroughly incorporated and evenly distributed to avoid creating sandy zones, changing the texture of the soil entirely. These zones can be problematic for plants as they grow.
Al-Kaisi explains, “When you change the soil texture, it’s going to change a lot of properties: the water-holding capacity and the water permeability; also, you get changes to soil pH and all other nutrient availability.”
Deep sand deposits that require a bulldozer or scraper to move will be expensive, but if you’re going to farm the land this year, you may have no other option. There is also the risk of creating ruts and compaction with the big equipment on saturated soil.
John Wilson, Extension educator at the University of Nebraska-Lincoln, recommends designating a single travel lane on the fields in order to limit the area of damage that can occur. Since that sand can’t be pushed back into the river, consider making stockpiles on the edge of fields or pivot corners. Sacrificing a few acres could allow you to salvage more over all.
And as far as gullies and cuts go – fill them up to 3 feet deep with sand and then put on topsoil to fill the rest of the space, again, to ensure consistent soil texture across your fields.
Maintaining Soil Health
If you don’t have the ability to plant this year, leaving a field bare will compromise the biology of the soil system and mean an even more challenging 2020.
For this reason, planting a cover crop – not for the yield – but to keep a root system alive, is best. The cover crop will rejuvenate the microbial community that promotes nutrient cycling in healthy, productive soil.
According to Al-Kaisi, “Biological damage is going to take place where this big assault of water and flooding stay on the field. When you look at it, fungi constitute about 50% of the microbial community in the soil system. So if we need healthy soil, we need these fungi to be in the soil to recycle nutrients for the plants.”
Al-Kaisi has a word of warning, “One of the cautions: there’s going to be a lot of snake oil trying to be pushed onto the farmers of inoculants and others to generate the microbial community. It’s not going to be a quick fix. This is why we are generally pushing for the use of conservation practices (like cover crops).”
As you manage your land this spring, be careful and thoughtful. Besides the sand, getting out in the fields before soil has been sufficiently dried can exacerbate the physical damage.
In addition to sand, which is isolated to certain areas, a widespread concern is what to do with cornstalk accumulation in fields. Like sand, layers of stalks can be tilled in and stockpiled at the edge of field. They can also be burned under the right conditions.
To John Wilson, one of the biggest unknowns we are facing now is how fast snow in the Dakotas will melt and cause flooding again in the swollen river area. The later it gets, the more likely the snow will melt fast. He says, “Farmers are debating whether to start fertilizing on ground and wonder if it is wasted money because it could be washed away.”