Very little rainfall in October throughout much of Iowa allowed most farmers to start and finish harvest without much delay. If conditions remain dry this fall, many farmers may be tempted to till the soil to allow any additional moisture to infiltrate. According to soil experts with USDA’s Natural Resources Conservation Service (NRCS), however, that is a common misconception.
Doug Peterson, regional soil health specialist with NRCS in Des Moines, says tilling the soil will actually accelerate the drying process and cause soil to erode more easily. He says the combination of high winds and warmer than normal temperatures wastes water if soils aren’t covered.
“Ground cover, whether it’s living or crop residue, limits the drying effect of wind, shades the soil from the sun, and traps snow during winter,” said Peterson. “This all adds up to more water infiltrating into the soil and less evaporating into the air.”
Peterson says soil should always be covered by growing plants, their residues, or a combination of the two. “Healthy soils are full of life,” he said. “Microorganisms living in the soil have the same needs as any other living creature needing food and cover to survive.”
An Iowa State University study (Al-Kaisi, 2013) tested the impacts of five different types of tillage systems on water infiltration. Results showed a no-till system allowed water to infiltrate three times more water than a system using a chisel plow, and about six times more water than a system using a deep ripper.
Barb Stewart, state agronomist with NRCS in Iowa, says farmers who planted cover crops this year are going to be even less affected by dry conditions. “The combination of residue cover and a living cover crop will keep soils healthy over the winter,” she said. “Cover crop roots offer soil microbes a reliable food source after corn, soybeans and other crops are harvested.”
Not only is tillage harmful to beneficial insects and other living organisms that affect soil health and crop production, but tillage also causes soils to erode much more easily. “When a falling raindrop explodes as it hits bare soil, it dislodges unprotected soil particles, and begins the process of soil erosion,” said Stewart. “Cover crops and plant residue prevent that violent splash on soil.”
Healthy, protected soils won’t crust over, allowing water to infiltrate the soil and become available to plant roots. Stewart says a mulch of crop residues and living plants on the soil surface also suppresses weeds early in the growing season, giving the primary crop a competitive advantage.
“Cover crops can build moisture reserves far better than row crops can by themselves,” says Stewart. “Cover crops open small channels in the soil for better water infiltration, and the organic matter they build helps retain both moisture and nutrients.”
For more information about healthy soils and soil conservation, visit your local NRCS office or go online to www.ia.nrcs.usda.gov.