of wheat, barley, and other crops differ in yield, disease resistance,
frost tolerance, drought tolerance, and other traits. The varieties
you grow on your farm are probably based largely on published
characteristics and yield reports from regional trials. Widespread
adoption of a new variety normally takes several years, or a
disaster with an existing variety. This time lag between an
improved variety's availability and acceptance can result in
profit losses for growers.
factors, such as crop rotation, herbicide use, fertilizer use,
tillage intensity, as well as local soil and climatic conditions
can influence the performance of varieties. For example, a disease
resistant variety may have consistently greater yields in fields
with a high level of the disease, even though it does not normally
rank among the top yielders in published tests.
tests allow you to measure the performance of new varieties
in your own fields in order to make the most profitable choices
for your farm.
are two types of on-farm tests:
regional tests with one replication per farm. This type
of test involves many growers within a particular zone. Each
grower agrees to put out one strip of each test variety, and
the data from all farms are combined to produce the replication
needed to draw statistically valid conclusions. The regional
test gives a good estimate of the relative performance of each
variety under different growing conditions. In order to be successful,
this type of test requires a well-planned effort and a minimum
of four to six farmers. Results from only one unreplicated location
can be very misleading, so it is essential that data from all
of the locations are scrutinized together. Your county Extension
agent can help you become involved in a coordinated, regional
test with multiple replications. If you are working as an
individual farmer you need four replications of each variety
in order to produce reliable results. This is the type of test
that will be discussed in this fact sheet.
AN ON-FARM TEST OF VARIETIES
objective in any on-farm test is to give the treatments being
compared (varieties in this case) an equal chance of performing
well. Long, narrow, side-by-side strips provide the most accurate
results. The strips should be positioned across the landscape
so that there is little chance that one strip is in a more productive
location than the others. For example, the strips in the photo
run across the hills. If strips are placed on the contour near
the bottom or top of a slope, the varieties on the bottom or
top will be growing in different soil and moisture conditions
than the varieties closer to midslope, causing a biased test.
On land leveled for irrigation, try to avoid
one strip where topsoil has been removed if its comparison strip
is where topsoil has not been removed.
It is best
to plant strips wide enough to allow one full combine cut down
the middle for yield determination. However, some farmers have
put one variety in each drill box, and plugged the end opener
so there is an extra space between strips. At harvest they carefully
cut each variety separately, working from one side. In either
case, weigh wagons or portable truck scales make it easy to
weigh the grain harvested from each strip.
of varieties. To keep the test practical and maximize accuracy,
the number of varieties tested should be kept small--two to
four is best. The more varieties tested, the wider each replication
becomes, increasing the likelihood that different varieties
will be growing in different soil conditions.
and width of strips. In general, the longer the strips,
the more accurate the test. In some very uniform fields, successful
tests have been performed in strips as short as 300 feet, but
strips of 700 to 1,000 feet or more will ensure that you are
able to detect differences between varieties accurately. If
the seed supply is too small for long, combine-width strips,
it is better to make the strips narrower instead of shorter.
of replications. We strongly recommend four replications,
that is, repeat the side-by-side comparison of all varieties
in four places. Replications can be next to each other in one
field, in different locations in a field, or even in neighboring
fields. Replication is the key to confidence in your results.
Randomization. After you have picked a place to put one replication, assign
varieties randomly to each strip within the replication. This
helps insure that some soil pattern affecting crop growth does
not bias the results. For example, if you are comparing three
varieties, find a place where you can place three strips side-by-side
and expect that they are in equally productive soil conditions.
Then draw names from a hat to decide which variety goes in which
strip. Repeat this process for each replication.
collection. Harvest each strip separately and record the
weight. Measure the length of each strip so you can accurately
calculate the area harvested. A wheel counter on the combine
can save time measuring distances. Make sure the moisture in
the grain of each variety is similar, or test grain from each
strip for moisture to allow correction of the yield results.
Test weight information is often helpful, so collect representative
samples for test weight determination. Any observations of differences
in germination, winterkill, lodging, disease, or insect damage
(or the lack of differences) should be written down for future
your results. A careful look at how the varieties compare
across all four replications will often reveal much about the
relative performance of the varieties. Are the differences between
varieties, averaged over replications, greater than the differences
from replication to replication? Some basic statistics will
help you decide whether small or inconsistent differences should
be taken seriously or not. Your county Extension agent can do
the statistics for you or you can obtain a simple computer program
from Oregon State University (see "Resources").
in varieties is not as risky or costly as other changes in farming
practices. This means we do not need to have as high a level
of confidence in our conclusions. For example, let's say we
did a test and the average yield of a new variety was three
bushels higher than our normal variety. There may have been
enough variation from strip to strip so that our Lease Significant
Difference (LSD) at a 5% confidence level was four bu/ac. This
means that there was more than a 5% chance that the three-bushel
difference we measured between varieties was only due to natural
variability between strips. Now suppose we calculate the LSD
at a 20% confidence level and find it is two and one-half bu/ac.
This tells us that there is less than a 20% chance that the
three-bushel difference in yields we measured was just due to
normal variability between strips. (In other words, an 80% chance
the difference was really due to differences in varieties.)
This might be enough confidence to plant a sizable acreage of
the new variety (after considering disease resistance, winterhardiness
and other characteristics) with the expectation that there probably
is a yield advantage. If you find the above confusing, remember
help is available from your county Extension agent.
A statistics program for simple field trials written for IBM
compatible computers. Send disk and postage return mailer, or
check for $5.00 made out to Oregon State University, addressed
to Russ Karow, Crop Science Building 131, Oregon State University,
Corvallis, OR 97331-3002.
Pacific Northwest On-Farm Test Results. Data and conclusions
from tests are compiled at the end of each year. Call the WSU
Crop and Soil Sciences Extension Office (509-335-2915).
Testing: A Grower's Guide, EB1706. B. Miller, E. Adams,
P. Peterson, and R. Karow. 1992. Washington State University
Cooperative Extension. A guide to designing and carrying out
OFT. Includes forms for record keeping. 20 pages. $1.00. Order
from WSU Cooperative Extension Bulletin Office (509-335-2857).
Test Record Form, PNW487. 1995. $1.50. Order from WSU Cooperative
Extension Bulletin Office (509-335-2857). A convenient form
to simplify planning and record keeping for on-farm tests.