Optimum seeding rates for Spring Wheat

Recommended plant populations for spring wheat are 250 plants per square metre. There has been a thought that producers may see a benefit to increasing plant populations with newer varieties.

A number of the AgriARM groups in the province undertook a two year study to look at what were optimum seeding rates and plant populations to arrive at the highest yields and economic returns. They used seeding rates in increments of 60 seeds per square metre from 60 to 480 seeds per square metre. Data collected included plant populations, grain yields and thousand kernel weights. In addition they calculated economic returns at seed costs of $9, $11 and $13 per bushel and grain prices of $100, $200 and $300 per tonne.

There were some results of note that only occurred in specific sites and years. At Indian Head with better growing conditions they found that lodging became a problem at higher seeding rates. Drier sites did not always have a yield increase with increases in plant density. Actual plant populations at the sites were more variable than expected. They were expected to be 80 to 90 per cent of the seeding rate. The range across the sites was 33 to 107 per cent of the seeding rate when 300 seeds per square metre were used as the seeding rate.

Optimum seeding rates for the maximum yield across these sites and years was 306 seeds per square metre. The optimum plant density to arrive at maximum yield was 191 plants per square metre. Maximum economic returns were achieved with seeding rates of 238 to 292 seeds per square metre. This was based on all the combinations of grain and seed prices. This would equate to a seeding rate of 90 pounds per acre with average seed size.

The full report of this trial can be found on the Western Applied Research Corporation website at www.westernappliedresearch.com.