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Soybean Planting Rate, Row Spacing and Planting Date (05/14/20)

North Dakota State University has a long tradition of recommending the establishment of a soybean population of 150,000 plants per acre across row spacings. This recommendation continues to exist across the state to optimize soybean seed yield.

North Dakota State University has a long tradition of recommending the establishment of a soybean population of 150,000 plants per acre across row spacings. This recommendation continues to exist across the state to optimize soybean seed yield.

This article summarizes the evaluation of data generated by 37 NDSU soybean planting rate and row spacing trials conducted during 2008 through 2019. A total of 390 data points (observations) comprise the database. Seed yield was normalized for each trial by comparing treatment mean (combination of seeding rate x row spacing) to the trial average. The treatment mean within each individual trial was divided by the trial average and multiplied by 100 to get the relative yield in percent (the trial mean was set at 100%). With all yield data on the same scale (relative percent) data was evaluated across trials. The blue dots in the figures represent the averaged relative yield for each factor evaluated. For example, in Figure 1, the blue dot for 100,000 planting rate is an average of 15 trial mean numbers and the 150,000 planting rate is the average of 27 trial mean numbers. The figures include trendlines and R-squared values.

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The average relative soybean seed yield among planting rates, ranging from 80,000 to 220,000 pure live seeds (PLS) per acre, and averaged across row spacings and all North Dakota site-years is shown in Figure 1. Planting rates of 125,000 to 200,000 PLS per acre generally provided above-average yield, with 169,000 PLS per acre optimizing yield. In eastern North Dakota trials, 8% of planted PLS per acre did not develop into viable soybean plants. Assuming that on average 8% of the PLS does not result in established plants and the general planting rate that provided highest yield across all trials was 169,000 PLS, we can expect about 155,000 established plants per acre to maximize yield.

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The average relative soybean seed yield among row spacings, ranging from 7- to 30-inches, and averaged across planting rates and all North Dakota site-years is shown in Figure 2. Based on the regression equation, the relative yield increases by 0.5% for each inch the spacing is narrower from 30 inches up to the 7-inch row spacing. Narrow rows (less than 15 inches) provided above-average yield, with 7-inch rows, based on the regression equation, providing about 106% yield compared to trial averages of 100%.

In a large survey of North Dakota growers during 2014-2017, producers were asked about planting date and yield. Figure 3 indicates that the yield potential decreases with later planting. The first half of May generally is an excellent time to plant soybean if favorable soil conditions exist.

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Hans Kandel

Extension Agronomist Broadleaf Crops

 

Greg Endres

Extension Cropping Systems Specialist

NDSU Carrington Research Extension Center

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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