Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
4/10/00
Contacts:
Mark Hanna, Extension Agricultural and Biosystems
Engineering, (515) 294-0468, hmhanna@iastate.edu
Elaine Edwards, Extension Communication Systems, (515)
294-5168, eedwards@iastate.edu
Tillage Options for Dry Weather
AMES, Iowa -- Minimal precipitation since harvest in much of the state suggests that many growers should carefully consider spring tillage options before going to the field.
"Generally tillage should be minimized to avoid loss of moisture already in the soil," said Mark Hanna, Iowa State University Extension agricultural and biosystems engineer. "A tillage pass could result in the loss of up to one-half inch of soil moisture or more. Conditions responsible for more moisture loss include dry surface winds with low relative humidity and a lot of sunlight. To a limited extent deeper tillage tends to let more soil aggregates be exposed to drying air conditions."
The choice of tillage operations will depend on how (or if) the soil has been tilled previously. Soil that has been left undisturbed since harvest last fall should be relatively moist in the top few inches from infiltration of any precipitation and the barrier effect of residue against moisture loss. For soils with adequate internal drainage, no-till may offer the best management choice.
Growers without recent no-till management experience will want to make sure their planters are properly maintained and adjusted, and carefully evaluate pest and nutrient management plans. For soils with poor internal drainage, light tillage with a field cultivator or disk just prior to planting will dry the surface enough to plant without causing undue moisture loss.
Soils that received primary tillage last fall may need to be leveled with a secondary tillage operation for planter operation. Two strategies (early spring or just prior to planting) may be used to conserve soil moisture.
"If early spring tillage is to be used, it probably should have been done by now or as soon as possible. With an early spring strategy, the soil is opened up for some drying, but spring rain that does occur can readily infiltrate the soil," Hanna said.
Using the second strategy, the tillage and leveling operation is delayed until as close to planting as possible.
"Any soil moisture present in the tilled depth is not allowed to begin to escape until about when the seed is planted. If tillage also is used for herbicide incorporation, consider label requirements and select herbicide and tillage timing accordingly," said Hanna.
Additional spring tillage issues include concerns about limited frost action during the past winter and sealing of soil around ammonia knives. Although warmer temperatures limited soil freezing to help break up compaction, many Iowa soils were dry enough during harvest that compaction was probably minimal.
"Even though some soils were observed to be 'hard' last fall as evidenced by increased tillage draft requirements, growers should recall that dryness causes soil to become hard," Hanna said. "Dry conditions rather than compaction could easily increase tillage draft."
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