2003, Issue #8

  from your Pioneer Sales Representative:  Kingston Feed & Farm

In 2003, Pioneer sales professionals and Field Sales Agronomists conducted 163 on-farm planting rate trials in North America to 1) better understand how growers select planting rates and 2) to test whether small plot plant population research results are applicable to commercial conditions.

Planting Rate Decisions Strip Test Layout

1. Current Planting Rate
2. Current plus 4000 seeds/acre
3. Current minus 4000 seeds/acre

How the Tests Were Conducted

Cooperators were asked to plant a Pioneer®Brand hybrid of their choice at their “current planting rate” and at 4,000 seeds per acre above and below that level. They were then asked to predict the harvest stand, grain yield and overall standability in the three strips. Then at the end of the season, cooperators collected stalk and root lodging counts, and plant population and yield results. A total of 64 different hybrids were used.

Grower Expectations versus On-Farm Results

Current Planting Rates: The average current planting rate per acre was 30,440 compared to an average of 27,845 from a 2003 North America marketing survey.

Stand Establishment: Growers accurately predicted stand establishment mortality rates or the difference between number of seeds planted and final plant population. Predicted: 6.7% mortality   Actual: 6.9% mortality.

Expected Income per Acre: On average, cooperators expected to earn $11.25 more per acre in the +4,000 planting rate strip compared to their Current Planting Rate (corrected for yield and seed costs).  In contrast, growers expected to realize a $11.25 income penalty from dropping their current seeding rate by 4,000 per acre.

Actual Income per Acre: At locations with adequate soil moisture, planting rates within +/- 2,000 of the optimum levels suggested by Pioneer Agronomy Science small plot research were the most profitable. On average, decreasing planting rates by 4,000 seeds per acre decreased net income $6.08 per acre. Under very dry or drought conditions, results were less clear. At low-yielding sites, growers could safely reduce planting rates below the suggested levels without a yield or income penalty.  More attention needs to be given to identifying optimum planting rates when very dry soil conditions are expected. 

Standability: Ninety percent of the cooperators expected that increasing their Current Planting Rate by 4,000 would worsen standability. However, this proved to be overly pessimistic. In fact, increasing planting rates by 4000 per acre significantly increased stalk lodging only 11% of the time and root lodging 4% of the time. Likewise, growers greatly overestimated the standability benefits of reducing their current planting rate by 4,000 per acre. While 69% of the cooperators predicted better standability in the lowest planting rate strip, improved stalk and root lodging was measured in only 6% and 2% of the locations, respectively.

Bottom Line

Pioneer small plot and on-farm strip plot plant population trials gave consistent results in favorable corn growing environments.

Modest changes in planting rate had only a minimal impact on stalk and root lodging. Selecting a hybrid with better stalk and root scores will reduce risk of standability problems much more than decreasing planting rates 1,000 to 2,000 per acre.

The Planting Rate Decisions Project will be continued in 2004 to include results from a wider range of growing environments.