April/May 1997
Steps to Better Stands of Wheat and Barley
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Prairie Grains is the
official publication of
the Minnesota
Association of
Wheat Growers,
North Dakota Grain
Growers Association,
South Dakota Wheat,
Inc., and the
Minnesota Barley
Growers Association.
By Jochum Wiersma
U of M Small Grains Specialist
Those of you who grow sugar beets go to great lengths to make sure you plant the optimum number of plants per acre, count stands accurately, and even replant if the number of beet seedlings is too low. Why would that story be any different for wheat and barley? True, wheat and barley are a lot more forgiving than sugar beets and have a greater ability to compensate for planting mistakes. However, initial stand is just as important with barley and wheat as it is with sugar beets.
To get the optimum stand, 30 wheat/barley plants per square foot, we have to make sure we plant enough seed. Unfortunately, many growers do not take enough time to make sure that the correct amount of seed gets planted per acre. If I may use a baseball analogy to respond: swing the bat blindfolded, and you have a greater chance of missing the ball.
To make sure you plant the correct amount of seed per acre, you will need to know the following things:
- The number of seeds per pound or 1,000 kernel weight in grams;
- The percent germination of the seedlot;
- The anticipated stand loss in your field.
Thousand kernel weight or its inverse, number of seeds per pound, varies for each variety. Genetically, some varieties have much larger seed than others. Pioneer 2375 is an example of a large-seeded variety. This translates to roughly 2,300 seeds per pound less for Pioneer 2375. That equals well over 200,000 fewer plants per acre when planting at the 1 ½ bushels per acre seeding rate many of you go by.
Bottom line: don't plant by weight, but by number of plants. Not just varieties differ, but between seedlots there are differences too. High test weights will result in fewer seeds per bushel.
The percent germination of a seedlot indicates the percent of the seeds that can produce a healthy seedling. Depending on the health of the seedlot, its age, and the storage conditions, the germination can drop dramatically. This means that more pounds of seed needs to be planted to adjust for a drop in germination as we are interested in healthy plants per acre, not the weight we planted.
An easy way to test germination is to count 50 seeds and spread them on a paper towel. Wet the paper towel until it is soaked, but not dripping. Keep the paper towel moist and at room temperature. Count the number of seed that have germinated and show a healthy sprout after 4 days and 7 days. Repeat this four times and calculate the average germination. If you use seed that was held over from two years or even longer, you may want to do a so-called 'cold stress test' in addition to a regular germination test. Old seed will lose vigor and although it may germinate, it may not yield a healthy viable seedling under field conditions.
The third component to the seeding rate equation is expected stand loss. Although seed might be vigorous, a percentage of the germinated seed will not produce a seedling. Even under ideal conditions you may expect a stand loss between 5 to 10%. Poor seedbed conditions can result in a 30-40% stand loss.
Taking all this into account, the seeding rate in pounds per acre is calculated by using the formula below.
- number of seeds per acre = desired number of plants per acre/(percent germination x [1-expected stand loss])
- number of pounds per acre = number of seeds per acre/number of seeds per pound
For a small seeded variety like Bacup, this calculates out to 100 pounds per acre or for a large seeded variety like 2375, this calculates out to 130 pounds per acre if the optimum for both varieties equals 90% and we expect a 10% stand loss.
Another step to getting an optimum stand is to make sure that the calculated seeding rate is also being planted. Calibrating your drill is crucial. All drills come with a manual or a table with recommendations for different crops. It is safe to say that those numbers are just an indicator, but not the precision you need. As featured on the cover of this magazine, the only way to make sure your drill is calibrated right is to test run it either before you enter the field or on the first pass in the field.
NDSU Extension Ag Engineer Vern Hofman has written an excellent article for in-field calibration, which may be found at the MN Wheat web site: www.small grains.org.