North Carolina State University Small Grains Specialist Randy Weisz recently showed a group of grain growers a series of large wheat plots planted at seeding rates ranging from 1.1 million seed per acre all the way up to 2 million seed per acre.

Weisz challenged the growers, back in mid-May, to tell him which plots were planted to which seeding rates. Few got it right.

“The point is, there appears to be very little difference in wheat, regardless of which seeding rate was used. On average that’s correct, but the averages can be deceiving and costly for wheat growers,” Weisz says

In similar tests, at the same farm near Rowland, N.C., last year, Weisz says average yields were only 2-4 bushels per acre higher from the top yielding plots to the lowest yielding plots.

Top yields came with a seeding rate of 1.3 to 1.5 million seed per acre, but there was very little difference in yield from 600,000 at the low end of the scale or 2 million seed per acre at the high end, compared to the highest yielding seeding rate.

Weisz conducted the same test at nine different locations and in one test the 600,000 seed per acre rate was the highest yielding seeding rate in the test. In a different test, the same low seeding rate was the worst yielding.

“This data is very important to wheat growers as they head into another fall planting season. At the low or the high end of the seeding rate chart, wheat yields vary greatly from farm to farm. One test is very high and another very low, providing a good average yield, but greatly increasing the risk factor, versus planting the more consistent seeding rate of 1.1 to 1.5 million seed per acre,” Weisz says.

Some of the ag dealers  in the southern end of North Carolina are recommending seeding rates of 2 million seed per acre. According to the North Carolina State wheat seeding rate tests, that rate is too high.

Again, the average yield is similar to what Weisz’s research team found with 1.3 to 1.5 million seed per acre, but the yield varied significantly from location to location.

Extra cost of seed

“By over-seeding the grower has a similar potential for yield loss as he does with 600,000 seed per acre, but he has the extra cost of the wheat seed. So, it could be a double-edged sword with losses in both yield and dollars spent producing the crop,” the North Carolina State specialist says.

“From a yield perspective, and based on our tests in North Carolina, I believe a seeding rate of 1.1 to 1.5 million seed per acre is optimum. However, farmers don’t usually look at optimum yield, they look at optimum profit,” he adds

“Based on 2011 wheat prices, the optimum seeding rate for optimum profit dropped to a range of 1 to 1.3 million seed per acre. The ideal comfort level may be higher, but the optimum sweet spot for profit appears to be at the lower seeding rates.

“Putting optimum yield and optimum profit together makes an on-time seeding rate of 1.3 million seed per acre look pretty good,” he says.

Just when it appears growers have an ideal seeding rate for maximizing profit, in comes some variables.

One of the biggest variables to seeding rate optimization is planting date.

If wheat is planted in the optimum time frame of late October to early November in the southern end of North Carolina, and if you look at the same seeding rate chart and the planting date is late November, then the optimum seeding rate for either comfort or profit is significantly different, Weisz says.

“If you are planting later than what is deemed the ideal planting date, seeding rate has to go up,” the North Carolina State specialist says.  If you miss the optimum late October planting date by a month, the optimum seeding rate for top yields is going to be somewhere between 1.5 to more than 2 million seed per acre, he adds.

“Based on several years of looking at seeding rates and planting dates, it seems that every week late that wheat is planted, seeding rates should be increased by 5 percent per week.

“On a profit per acre base, being a month later than optimum planting will require about 1.5 million seed per acre, Weisz says. From a comfort standpoint, the optimum rate may be closer to 2 million seed per acre.”

While researchers deal in number of seed per acre, most growers calibrate planters and deal more frequently with pounds of seed per acre.

Simple conversion device

The North Carolina Grain Growers Association recently developed a simple calculator/slide rule that will make that conversion for the grower. “It’s a neat little tool that is easy to use to convert seed per acre to pounds of seed per acre,” Weisz says.

On side one of the tool a grower can convert seed per acre to pounds per acre.

On the other side of the calculator they can factor in where in North Carolina they are located, what is the ideal planting date and using that data to calculate the optimum pounds of seed per acre, he adds.

For even more precise planting, the tool will also convert pounds of seed per acre to seed per drill row foot of row.

Weisz cautions growers to not depend on the seeding rate on the table on your grain drill because it is almost always wrong, and is often way off.

“We often do tests on grower farms and in the past have used their planting equipment.

“In one test we were trying to put out 100 pounds of seed per acre and used the information on the planter. In reality we were putting out 190 pounds per acre,” Weisz recalls.

“If you look at the fine print on the manual that comes with some of the grain drills, you will find that the manufacturing company bases the recommendations on a computer model. “They know the charts on the planters are just a rough estimate,” he adds.

Using the planting tool provided by the North Carolina Grain Growers Association, a grower can get the seeding rate right without spending a lot of time converting seeding rates from seed per acre to pound per acre to seed per foot of row.

Getting the seeding rate right, and getting it right based on planting date can both save and make a grower a lot of money.

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