Soybean populations in 30-inch rows

Soybean seed cost and potential for decrease in white mold severity drive interest in decreasing seeding rates.

Michigan State University Extension educators who work with the Thumb Ag Research and Education (TARE) project evaluated four soybean seeding rates: 80,000; 100,000; 130,000; and 160,000 seeds per acre. The plots were established in a randomized complete block design with four replications. The variety planted was NK S21-M7 Brand.

The plot was established near Fairgrove, Michigan, in Tuscola County on clay loam ground with good fertility (in ppm—P 49, K 155, Mg 315, Ca 2218, pH 7.5). The soybeans were planted in 75-foot by 15-foot plots and were planted perpendicular to the field tile.

The table below shows the planted population, the stand count at harvest, yield and per acre seed cost ($67 for 140,000 seeds) for each of the planting rates.

Planted population

Harvest stand count

Yield (bushels per acre)

Per acre seed cost

160,000

151,000

69.4 a*

$76.57

130,000

122,000

67.9 ab

$62.21

100,000

92,000

65.8 bc

$47.86

80,000

73,000

65.0 c

$38.29

CV (%) = 2.6

LSD (0.05) = 2.8

*Yields followed by the same letter are not significantly different.

The field was not infected with white mold. No observations could be made relative to the effect of seeding rate on incidence of that disease.

The 160,000 and 130,000 seeding rates produced the greatest yield. These results agree with the recommendation of planting soybeans at a rate that results in a final population that is greater than 100,000 plants per acre.

The Michigan Soybean Promotion Committee provided funds that helped make this study possible.

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