Leaving crop residue on the soil surface improves nutrient cycling and, ultimately, soil quality that will increase and sustain soil productivity. Through conservation practices that include balanced crop residue management and soil fertility, environmental quality can be substantially enhanced.

“By retaining crop residue on the soil surface, soil organic carbon content and the soil’s nutrient-holding capacity are increased while protecting the soil from wind and water erosion,” explains Mahdi Al-Kaisi, Iowa State University Extension soil management specialist. “Wet conditions experienced in Iowa this past year demonstrate the value of leaving crop residue on the soil surface to reduce surface runoff, sediment loss and associated nutrient losses.”

Amount of nutrients lost depends on several factors
Alternative uses of corn residues for various purposes, such as baling residue for animal use or for ethanol production from lignocellulosic biomass, may have adverse effects on soil and water quality, he says. The reduced nutrient supply associated with corn stover removal represents an economic loss in the short term, but it will have a long-term negative effect on soil quality, water quality and agriculture sustainability.

The quantity of nutrients lost with stover removal depends on residue type, amount of residue removed, soil type, climate, soil organic matter, rate of residue decomposition, tillage and other management practices. If unsustainable amounts of stover are removed from the field, wind and water soil erosion will intensify while accelerating the loss of soil organic carbon and other nutrient levels, and potentially can reduce future yields.

Short-term and long-term effects of crop residue removal
Residue removal in Iowa may have a small effect on soil productivity in the short term due to rich organic matter soils. “However, this will not be a sustainable practice in the long term as demonstrated by many studies where the acceleration of soil and nutrient losses were significant,” says Al-Kaisi. “Long-term effects of removing high levels of corn residue can lead to net losses of nutrients under standard fertilization practices.”

In a normal rainfall, raindrops 6 millimeters in diameter hit the ground at 20 miles per hour. The cumulative impact of raindrops can be incredible, dislodging soil particles and "splashing" them up to 3 to 5 feet away. The splashed particles clog soil pores, effectively sealing off the soil surface and leading to soil crust and poor water infiltration. Instead of soaking into the soil, water collects and moves down-slope in sheet or rill erosion, forming gullies and carrying soil particles to rivers and streams.

In addition to the amount of residue left on the soil surface, the manner in which residue is harvested and the uniformity of residue distribution on the soil surface to prevent potential soil erosion must be considered. For more information read the online article: How residue removal affects nutrient cycling.

Soil Health Conference
The environmental effects of residue removal and conservation practices will be discussed at the upcoming Soil Health Conference in Ames Feb. 16-17. The two-day conference will focus on addressing management practices that sustain a profitable agricultural systems while protecting the environment. The goal is to increase awareness and understanding that soil health is pivotal to sustainable agriculture and environmental quality in Iowa and the Midwest.

Presentations at the conference will address concerns and interests of farmers, agronomists, agricultural consultants, soil scientists, Extension professionals and policy makers and will appeal to those who are interested in learning about soils for sustainable agriculture. This conference will provide an opportunity to certified crop advisers who are eligible to earn continued education credits in soil and water by attending the many breakout sessions.