January is a time of year when very little activity is going on in the
field. But growers are making management decisions critical to next fall’s
harvest. In all crops, yield potential is set when variety selection is
made. Agronomic and pest management practices can maintain the genetic
yield potential of a variety by minimizing limiting factors, but they
cannot increase it. This places a premium on variety selection and on
the way it is done.
selection is not about identifying which lines did best over the past
year – it is about predicting which lines will do best in the
quote by Jim Rouse at Iowa State University points out the pitfall of
only looking at the top of last year’s variety test and lays out a
method for picking varieties.
is the result of the interaction between genetic potential and
environment. A variety should be chosen because it has the genetic
characteristics to perform well given the field’s environment. While
yield is always the ultimate goal, selecting a variety from a trial
based solely on yield without regard to the environmental conditions in
which it grew may not result in good performance in the future.
to the claims of local meteorologists, predicting rainfall patterns and
temperatures for the coming growing season is unattainable. But, when
attempting to predict growing conditions for the upcoming year, growers
know a great deal about the environment in which their crops will
develop. A grower knows soil characteristics, fertility levels, crop
history and the past incidence of pests and pathogens.
choosing a variety, the first criteria should be availability.
Management plans based on which are in short supply usually end up
including poorly adapted varieties added at the last minute.
second decision should be which, if any, GM traits are needed. The
benefits of these traits are great if they eliminate a pest which is a
limiting factor or fit into a weed control system already in place.
third decision is the defensive traits needed to minimize limiting
factors. These traits include disease resistance, insect resistance,
nematode resistance, lodging and shattering potential, fallout in cotton
and tolerance to stress. While things like disease resistance or fallout
are not normally considered before yield potential, consider that a
variety will not be able to reach its yield potential if overwhelmed by
a limiting factor.
last and most discussed decision in variety selection is yield
potential. Traditionally, the standard for proving a variety has been
three years. Three years is now the life span of many varieties. With
the EPA extension of the Bollgard™ license in cotton set to expire in
2009 and genetic advancement in corn hybrids occurring at a pace of two
bushels per year, it is now necessary to evaluate and select varieties
in a short period of time.
how do we go about "predicting which lines will do well in the
future" when faced with limited years to gather data? To choose a
variety that will perform in an unknown environment, look at performance
data across as many environments as possible. Choose the variety that
performs well in all of them. When faced with limited years, increase
the number of locations looked at each year.
sources of information on yield performance are available from
universities, Extension, seed companies and growers. All of these need
to be considered. Though data from trials with similar limiting factors
is beneficial, looking at locations with a different set of limiting
factors is just as important because good performance in both shows
stability in variety performance. It is very important to know the
source of the information used, so you can be aware of the type of
environment the trial was conducted in and the quality of the data. This
is easy with university and Extension data; they usually publish
agronomic and trial quality with the results. It can be more difficult
with seed company data, but trials conducted on farm by seed companies
can provide practical information and are important to consider. A good
practice to insure quality information is to visit trial locations
during the growing season.
following websites provide variety information:
will be conducting corn, cotton, soybean and wheat variety trials during
the 2008 growing season in many parts of the state. This will be
provided by Agri-AFC as a service to growers in Alabama. Information on
the trials and yield results will be available through local Co-op
Meyers is an agronomist for Agri-AFC. Contact him at [email protected].