Temperature, Residue, and Yields From Different Tillage Systems
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The best tillage system for your field or farm will vary depending on soil
type and, on an annual basis, by spring weather conditions. Since weather cannot
be predicted ahead of spring planting, one needs to select a system that will
provide a consistently good seedbed across a range of climatic conditions while
still maintaining adequate erosion control. A reduction in tillage trips will
increase residue cover on the soil surface, and thus reduce erosion potential.
Unfortunately, this increase in residue cover may result in cooler, wetter soils
that may result in delayed emergence and slower early-season growth. Many farmers
are adopting conservation tillage systems not only to reduce erosion potential
but also to reduce labor and equipment costs. The system you select must have
a balance between input cost and consistency of yield over time.
Crop residue management (CRM) is an excellent technique to minimize erosion.
The term CRM refers to a philosophy of year-round management of residue that
will maintain the level of cover needed for adequate control of erosion. Conservation
tillage, which is defined as a system that provides at least 30 percent cover
after planting, will help meet the goals of crop residue management. Several
tillage systems are classified as conservation tillage. These include no-till,
strip-till, and mulch-till. Adequate erosion control may require more than 30
percent residue cover after planting. In those cases, additional conservation
techniques or structures may be needed to attain the necessary erosion reduction.
No-Till and Strip-Till
With no-till, the soil is left undisturbed year round, except for the soil disturbance
in a narrow band created by a row cleaner, coulter, seed furrow opener, or other
device attached to the planter or drill. No-till planters are usually equipped
with row cleaners to clear row areas of residue. No-till planters and drills
must be able to cut residue and penetrate undisturbed soil. Strictly speaking,
a no-till system does not allow operations that disturb the soil other than
the planting or drilling operation. Some producers apply anhydrous ammonia,
thus disturbing some of the soil.
A modification of the basic no-till system is strip tillage, where the near-row
zone is tilled, typically in the fall, and often in conjunction with fall anhydrous
ammonia application. This system incorporates some of the theoretical advantages
of tillage (soil drying and warming) with those of no-till (residue cover for
erosion control).
Mulch-Till
Mulch-till includes any conservation tillage system, other than no-till, strip-till,
and ridge-till, that maintains a minimum 30 percent crop residue cover after
planting. Tillage might be performed with a subsoiler or chisel plow; tillage
before planting might include one or more passes with a disk harrow, field cultivator,
or combination tool. Crop cultivation may be used to aid in weed control; however,
tillage tools must be equipped, adjusted, and operated to ensure that adequate
residue cover remains for erosion control, and the number of operations must
also be limited. This system is commonly used in Illinois.
SOILS Statewide Tillage Study
A statewide study was commissioned in 1999 by the Illinois Department
of Agriculture to study corn production under no-till, strip-till, and
mulch-till tillage systems in field size demonstrations. Twelve sites
were selected, and a variety of parameters, including soil temperature,
residue cover, emerged plant population, and final grain yield, were measured. The data from 11 of the sites combined
showed identical yields for no-till and strip-till. Also shown are average
yields from nine of the sites, excluding two low-yielding and variable
sites from southern Illinois. This data shows a slight increase in yield
with tillage, but this difference is not significant, meaning that we
don't have much confidence that type of tillage affected yield at all.
Strip-till benefits over no-till would be more likely in a spring that
was cooler and wetter than 2000. This study will continue in 2001.
Greater in-row and inter-row residue levels were found in no-till (N)
treatments with strip-till (S) being intermediate to no-till and mulch-till,
here indicated as C, chisel plowed.
Temperatures recorded in-row were cooler with less tillage. The average daily cycle of soil temperature for two sites is shown
in Figures 4 and 5. At a central Illinois site, the temperatures were
similar for strip-till and mulch-till during the warmest part of the day, while later in the day, temperatures
under strip-till were similar to that under no-till. At a site near the
Quad Cities, diurnal fluctuations in temperature were more sensitive to
tillage.
University of Illinois Study
A two-year study at three locations in Illinois-Urbana, Monmouth, and
DeKalb-was designed to investigate the interaction of tillage and N application
timing. Across all tillage systems, spring-applied N gave the greatest
yield. Strip-till and chisel-plow systems
gave a nearly identical yield for different N application timing.
Summary
Tillage systems may affect crop residue distribution, soil density, and, subsequently,
water and temperature relationships in the germination zone. Differences in
soil properties do not always translate into significant grain yield advantages
for one particular tillage system over another. Weather conditions in the early
part of the growing season help determine the likelihood of crop response to
tillage systems.