Tillage: Benefit or detriment?

By Josh Kamps, Lafayette County agriculture educator

Preparing the soil for next year’s crop is an important area of crop production. Tillage is a commonly chosen practice to prepare soil ahead of planting by burying crop residue, incorporating applied nutrients, or loosening compacted soils. Simply stated, tillage is the mechanical modification of soil in preparation for crop production. Depending on the type of soil and the type of tillage, soil health is at risk with routine tillage.

Soil health is a measure of the ability of soil to function properly. Healthy soil has an even balance of physical, chemical and biological characteristics. Examples of proper soil function include equal balance of water to air, symbiotic plant to soil microbe relationships, and adequate levels of available crop nutrients.
The results of a three-year field and laboratory study at Iowa State University report no significant difference for the rate of Bt corn residue breakdown between tillage or no-till. Burying the residue, processing the residue into smaller pieces or applying decomposition agents did not show an increased rate of decomposition.

In healthy soils with adequate soil microbial activity, the maximum residue decomposition rate occurs when soil moisture is at field capacity and soil temperatures are above 50 degrees F. Putting corn residue in close contact with healthy soil begins this process on the soil surface. Tillage as a residue management tool does not address the main driver of decomposition, which is soil biological health and proper soil conditions.

The importance of incorporating soil-applied nutrients is specific for each nutrient. Nitrogen losses resulting from surface application due to volatilization are common during certain weather conditions. Incorporating crop nutrients through banded placement can promote crop production efficiency. Certain reduce-till options and planter set-ups are available to accomplish this process. Healthy soils with established cover crops and microbe activity transport nutrients from the soil surface to the plant-rooting zone. Earthworm and root channels along with adequate water infiltration levels provide the necessary route. Cover crop research completed at the University of Minnesota reported a significant reduction in soil nitrate level following manure application with a rye cover crop compared to no rye.

Soil compaction is a result of applied pressure to the soil surface during times the soil is at or near field capacity. Compacted soil has reduced soil aggregation, which leads to lower water infiltration, limited soil biological activity and limited plant root penetration. Excessive soil compaction limits a soil’s ability to function properly and limits crop production. As soil moisture decreases, air pockets form between soil aggregates, which increases the soils’ load-carrying capacity. A soil penetrometer or a soil spade are both tools capable of identifying the presence and depth of soil compaction. If consistent compaction across a field is not present, a tillage pass may increase the risk of soil compaction in the field.

Healthy soils balanced for physical, chemical and biological characteristics are equipped to resist erosion. Strong soil aggregates, living roots and increased soil microbe activity come with less tillage. Healthy soils infiltrate and store water and capture and store carbon, which increases soil organic matter levels. The first step towards healthier functioning soils is to take a step back and determine the reason for choosing a tillage pass.