Madison, Wisconsin
March 16, 2009
While there may be no
particular advantage for planting soybean early, there was a
clear disadvantage for planting late.
MADISON, WI, March 16, 2009 -- Planting soybean on the optimum
date produces maximum yield and profit without increasing
production costs. Unfortunately, the optimum planting date is
hard to indentify, because it varies from year to year,
depending on the weather and how much it rains and when it
rains.
"Planting date has been a favorite topic of researchers ever
since soybean was introduced into the United States, so there is
a large database of experiments in the literature. A combined
analysis of this database will provide a clearer picture of the
average response than any single experiment," explains Dr.
Dennis Egli, University of Kentucky, Lexington.
Dr. Egli and colleagues at the University of Kentucky analyzed
the combined results of planting date experiments and published
their findings in the March-April 2009 issue of the Agronomy
Journal.
The scientists analyzed combined results of planting date
experiments from the Midwest (NE, ND, IA, IL, IN, and OH), the
Upper South (AR, KY, MO, and TN), and the Deep South (AL, FL,
GA, LA, MS, and SC). Planting dates varied from mid-April (early
April in the Deep South) to July. The experiments included
several varieties and several row spacings, but none were
irrigated.
In spite of the differences in environmental conditions and
varieties from the Midwest to the Deep South, the response of
yield to planting date was remarkably consistent across the
three regions. Average yield did not change as planting was
delayed from mid-April until late May or early June. Thus, there
was no evidence that April plantings produced higher yields in
any of the three regions. Early April plantings were included in
the Deep South and average yields decreased for these
ultra-early plantings.
A previous study published in the Agronomy Journal [Vol.
101:131-139 (2009)] concluded that April and early May plantings
in Indiana consistently produced the highest yield. But our
results, based on the combined analysis of 28 experiments, show
no significant advantage for such early plantings from the
Midwest to the Deep South.
While the results of this analysis show no consistent yield
advantage for planting early, there was also no consistent yield
loss (except for ultra-early plantings in the Deep South)
associated with early plantings.
"If the soil is ready for planting in April, producers should
feel free to plant, but they shouldn’t expect higher yield,"
advises Egli.
Planting into cold, wet soils, however, can reduce seedling
emergence and stand, which may require replanting to avoid yield
loss. Unacceptable stands may be more common if seeding rates
are reduced to the minimum to reduce seed costs.
Average yield declined rapidly when planting was delayed after
30 May in the Midwest, 7 June in the Upper South, and 27 May in
the Deep South at rates ranging from 0.7 (Midwest) to 1.1 (Upper
South) and 1.2 ( Deep South) percentage points per day. At these
rates, delays of just 2 weeks will reduce yields by
approximately 10 to 20%.
There may be no particular advantage for early planting, but
there was a clear disadvantage for planting late, after the
critical date in late May or early June. Soybean producers can
maximize their yield and profits by making sure planting is
completed before the critical date.
The full article is available for no charge for 30 days
following the date of this summary. View the abstract at
http://agron.scijournals.org/cgi/content/full/101/2/330.
A peer-reviewed international journal of agriculture and
natural resource sciences, Agronomy Journal is published six
times a year by the American Society of Agronomy, with articles
relating to original research in soil science, crop science,
agroclimatology and agronomic modeling, production agriculture,
and software. For more information visit:
http://agron.scijournals.org. |
The American Society of
Agronomy (ASA) is a scientific society helping its 8,000+
members advance the disciplines and practices of agronomy by
supporting professional growth and science policy initiatives,
and by providing quality, research-based publications and a
variety of member services. |
|
