Background on Value Web Component: Agronomic Production
Background
Producing a soybean crop could be as
easy as putting seed into soil, waiting till
maturity, and harvesting. You may even get
lucky and have seed worth selling. However,
obtaining profitable yields and high seed quality,
as well as contributing to increasing demand and
maintaining our natural resources, requires
careful planning and thoughtful investment.
“You’re only as strong as your weakest link.”
Soybean yield potential is genetically
predetermined. However, achieving that
potential relies on optimal environmental
conditions and sound agronomic practices.
Today, soybean yields average 43 bu/acre in the
U.S. and 35 bu/acre world-wide, yet yields
between 100-155 bu/acre have been observed.
How can we achieve the maximum?
Systematically, to maximize yield potential,
producers must take an approach that strives to
optimize every component of the production
system, from seed selection, time of planting,
pest control and nutrition management, etc., all
the way to harvest. Failure to address even one
factor can limit production.
In agriculture,
understanding how various
aspects of production can
influence yield is illustrated
by Liebig’s barrel (See
Figure). Just as the shortest
stave determines the capacity
of a barrel, yield is determined by the most
limiting factor.
nodulation and nitrogen utilization, as well as
the availability of essential nutrients including
iron, potassium, phosphorous, and manganese.
In addition to abiotic factors, weeds,
insects, parasitic nematodes, and disease, also
contribute to plant stress and minimize yield
potential. Weeds compete with soybeans for all
major resources including water, light, space,
and nutrients. Weeds also lead to contamination
of harvested seed and can provide an alternate
host for insects and pathogens. Nematodes and
insects feed on and damage various tissues
interfering with photosynthesis, seed
development, and water and nutrient uptake.
Often, these effects are subtle or are hidden
below ground. In addition, these pests can also
serve as vectors for pathogens while feeding
damage can lead to secondary infections. Like
nematodes and insects, pathogens interfere with
basic plant development resulting in root rots,
seed rots, leaf chlorosis and necrosis, stem
lesions and cankers, and vascular wilts, all of
which can result in plant death.
Overall, the greatest limitation to
production is grower education and awareness of
these factors. In the end, you cannot improve
yield if you don’t know what factors to manage
or how these factors interact with each other.
Moreover, although we have tools to monitor
field conditions and to collect and analyze huge
amounts of data (enabling producers to make
better, more informed decisions), they are not
being used. This is an area of modern soybean
production that is underutilized.
Limitations to Value Realization
Variety selection, time of planting,
planting depth, seed population, row width, soil
quality, weed and pest management, and
environmental conditions, are only a few factors
growers need to consider when developing a
strategy for optimizing yield. Impacting each of
these decisions are those factors that limit
production. Early planting favors high yields but
soybeans require soil temperatures between 5560°F for optimum germination and seedling
development. Insufficient moisture can also
delay germination while too much moisture can
lead to compaction and crusting, resulting in
reduced emergence. Soil pH outside the optimal
range of 6.0-6.5 also limits yields by affecting
Problem Overview
Maximized yield potential is achieved
when all factors are optimized. Unfortunately,
there are no “silver bullets” or easy solutions
when addressing the various limitations to
soybean production. Growers must take a
multidimensional approach when developing a
production strategy. Variety selection forms the
basis of any production strategy. Once a variety
is chosen, every other decision will be made in
an effort to capitalize on its genetic yield
potential. Within the last 10 years, high-input
management practices have been promoted as a
means of increasing yield, primarily through
physiological or “plant health” effects. As a
result, there has been a dramatic increase in the
Example of Complex Issue Affecting the Agronomic Production
use of pesticides in soybean production. The
common practice of uniform pesticide
applications as a means of insuring no pests may
not be providing the economic returns or pest
protection desired.
What’s Been Done to Address Problem
The following example demonstrates
that effectively addressing “agronomic
production” issues requires extensive
collaboration and cooperation across several
disciplines—an approach that has made Purdue
University a leader in understand and managing
complex issues. In 2009, Purdue University
extension specialists Drs. Kiersten Wise (plant
pathology), Bill Johnson (weed science), and
Christian Krupke (entomology), initiated a
project to study the impact of foliar fungicide
and insecticide applications on soybean growth
and yield when disease and insect pressure were
minimal to test the idea that high intensity
management may not provide the best solution
for yield and pest management.
Small-plot field trials were established
on three Purdue farms around the state from
2009 to 2012 and included varying combinations
of glyphosate (herbicide), Headline (fungicide),
and Warrior (insecticide). Complementary largescale trials were also established from 20102013 in multiple locations throughout Indiana.
These trials included applications of glyphosate
alone, Headline alone, or Headline+Warrior in
combination.
Results from the small-plot trials
indicated that applications of fungicides and
insecticides when disease or insects weren’t
present improved yields but the increase
depended on timing of the application and was
inconsistent from year-to-year. Likewise, data
from the large-scale trials indicated that
“insurance” applications were associated with
higher yields, but this increase was dependent
upon the region. Based on economic analysis of
these studies, high-input management practices
as a means of improving soybean yield, was
economically practical only 30% of the time. As
such, Purdue University advises growers to
monitor their fields for disease and insects and
to apply fungicides and insecticides only when
and where appropriate. Doing this can prolong
the efficacy of these chemicals while saving as
much as $40/acre in application costs.
Reaching these conclusions required
collaboration among agronomists, plant
pathologists, entomologists, and economist from
research and Extension. The research has
fostered national interest in information on
fungicide efficacy and proper usage, resulting in
the first national soybean fungicide efficacy
table (Purdue Extension Publication BP-161-W)
and the popular “Fungicides for Field Crops”
publication.