Boosting crop yields starts at ground level – with soil structure. Soil’s composition and microorganism density help determine its productivity.
“The best way to improve soil structure is to not destroy it,” says Ellen Phillips, University of Illinois Extension educator. “Once soil structure is damaged, it can take many years to recover.”
Heavy equipment that collapses the soil structure can be devastating, with up to 50% yield hits. And while that total collapse of the soil structure may be limited to a small area of a field, it also stands to reason that even slight disruptions can impact yield, notes Tom Halbach, professor and Extension educator at the University of Minnesota Department of Soil, Water and Climate.
“When the soil structure collapses, it forces out water-holding and gas-exchange soil capabilities,” he says. “And damage one year or two years in a row might not be immediately noticeable, but it’s there, and it’s trimming yield potential because soil-structure loss is an ongoing threat to soil fertility. Once lost it’s incredibly difficult to get back.”
But even with the best intentions, damage to the soil structure can occur. Perhaps it’s a planting window that’s closing fast, so running a planter over wet soils is the only option. Or, it’s December and a wet corn field just can’t wait to be harvested. “Sometimes the choices are difficult, and even the best management can result in some damage to soil structure,” Phillips says.
And while rebuilding soil structure can be a long road, it is not impossible. In fact, it can be a part of any farming operation.
We talked to three soil experts to get their take on how to best improve soil structure:
“Crop rotations can go a long way to improving soil structure,” Phillips says, adding that wheat is an excellent crop to add to the rotation. “Small grains have an extensive root system and more organic material. The very extensive and deep roots help put more organic matter into the soil.”
Even mixing in another crop besides corn and soybeans every few years can help. “Soil structure can be recreated through a freeze-thaw cycle, wet-dry cycle or by adding organic matter. That diverse porosity of a soil with good structure is very important, because roots can’t just push through the soil – they grow by moving through its pores. And that can mean a better root system, and in turn a better upper part of the plant.”
Bring the residue back
The increased interest in harvesting crop byproducts has Halbach concerned. “The way to good soil structure is returning organic matter to the soil. That’s difficult to accomplish if we are harvesting everything,” he says. “We may not see the damage immediately, but we can’t think about soil structure in a two- to three-year window. We need to think about the next 10 years or more.”
His advice is simple: Improve soil structure by incorporating residue back into the soil.
And one source is manure. “It helps feed soil organisms and can provide an excellent boost to a soil’s structure,” Halbach says.
Dale Mutch, Extension specialist for IPM/cover crops at Michigan State University, promotes the cover crops to get more organic material back into the soil, break up crop rotations and maintain root structure in the soil for a longer time.
One way growers can effectively incorporate various cover crops into their current rotations is aerial seeding before harvest. Producers are starting to plant cover crops such as rye, winter peas or radishes when soybeans are at 10% yellow leaf, or when corn is at black layer and starting to dry down. This opens up the canopy to allow seed to reach the soil. Some farmers chop corn-plant tops to increase seed-to-soil contact when aerial seeding, improving germination before corn harvest, Mutch says.
Soils differ as much as growers do. “Producers should not expect to just go in and do one thing to improve soil structure,” Mutch says. Crop rotation, residue accumulation and cover crops can go a long way to help.
Free organic matter?
While producers may see some economic benefit from harvesting additional biomass from their soils, experts are also looking at other ways to identify potential sources that can be incorporated into the soil.
“There are a lot of waste materials that could potentially be excellent organic matter sources for soils,” says Tom Halbach, University of Minnesota professor and Extension educator. Growers may overlook paper mills, sewage facilities, food-processing facilities or even municipalities as a source of residue enrichment.
Halbach’s research is working with these sources to determine the best ways to deliver these products to growers. If you’re located near a city with residential leaf collection, cities are often desperate to get rid of leaves, and they can make an excellent organic-material addition to the soil.
Ellen Phillips, Extension educator at the University of Illinois, has developed a pilot program that matches horse farms (with excess manure) to growers.
“Many horse stables in our area have 10-12 horses and have to pay to have it hauled, often resulting in it going to a landfill,” she says. “Sometimes these horse stables will pay you to haul the manure away.”
And with one horse producing up to 12 tons of manure and bedding a year, that’s a lot of waste that could be returned to the soils.