Most of Minnesota cropland experienced below normal rainfall in the past six months. As a result, soil water levels are low. Normally, soils "recharge" moisture during the fall season when rainfall occurs and plant uptake is nearly non-existent.
This recharge also occurs with spring rainfall when most crops aren't in yet to consume the moisture. Data from the University of Minnesota's Southwestern Research and Outreach Center in Lamberton indicated that soil water recharge and crop usage is not in a normal pattern this spring.
When the ground froze last fall, there were about 3 inches of plant-available water in the 5-foot soil profile, with most of it below 2 feet. A normal profile would hold closer to 10 inches of plant-available water. Add to this the below-normal snowfall that did not add significantly to spring recharge.
Most tillage done last fall was aided by winter snowfall. Fall chisel plowing provided a rough surface that provides divots for water storage during snow melt and early spring rains.
Conservation tillage done last fall also is aiding in soil moisture retention by leaving significant residue in the fields, reducing soil water evaporation and increasing infiltration during spring rainfall. Last fall, tillage was difficult at best because of the dry conditions. Large, hard clods were created with the fall tillage. It looks like the moisture we did get this winter mellowed the clods enough that a tillage operation will be able to create a good seedbed this spring.
Keep tillage minimal this spring to conserve soil moisture and maintain residue on the soil surface. Seedbed preparation must be the goal of spring tillage.
Any clods from last fall should be worked for good seed-to-soil contact at planting. Spring tillage is necessary in most cases. However, take care not to get too aggressive because excessive tillage will dry out the soil and cause a dry seedbed. This will cause problems with plant stands and thus affect grain yield even if we receive adequate amounts of moisture during the growing season.
For more information, visit the University of Minnesota Extension website at www.extension.umn.edu/tillage.
-By John Moncrief, University of Minnesota Extension soil scientist.