Soybean Response to Seeding Rates in 30-Inch Row Spacing

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1 Background Choosing the optimal soybean seeding rate can improve profitability in soybean production. Many recent studies on soybean seeding rates in the High Plains suggest that higher seeding rates may not result in significant yield and profit increases. Results from a study by the University of Nebraska suggest that a seeding rate of 120,000 seeds/acre on 30-inch rows can maximize profit potential. 1 This recommendation was based on a cost of $40 to $65 per bag of seed and market prices at the time of the study ( , 2010, and 2013). In a 2010 Monsanto Learning Center study at Gothenburg, NE, a seeding rate of 125,000 seeds/ acre was found to maximize profitability. This recommendation was based on a seed cost of $68 per bag and a soybean market price of $10 per bushel. This study also demonstrated the ability of soybean plants to compensate for lower plant stands by increased branching and pod production. A follow-up study conducted in 2014 demonstrated that potential profitability of different seeding rates was greatly affected by market price. When considering a soybean market price of $10.40 per bushel, the highest profitability was achieved at a seeding rate of 100,000 seeds/acre. When soybean market price was higher, $14.50 per bushel, the highest profitability occurred at a seeding rate of 260,000 seeds/acre. Study Guidelines A soybean demonstration trial was conducted at the Monsanto Learning Center near Gothenburg, NE in 2015 to continue to evaluate how soybean seeding rate affects stand establishment, yield, and profitability. A 2.4 MG soybean product was planted at six different seeding rates: 60,000, 100,000, 140,000, 180,000, 220,000, and 260,000 seeds/acre. Potential profitability was considered by accounting for different seed costs on a per acre basis and varying soybean market values. and strip tillage was performed on April 16, 2015 to facilitate planting through corn residue. The trial was planted on May 27, 2015 in 30-inch rows. Irrigation was applied as needed to prevent moisture stress and the field was managed to remain weed free. The trial was designed as a randomized complete block with five replications. Each plot measured 40 feet by 10 feet. Data was collected from the center two rows of each plot. Results and Discussion Average yields steadily increased with increasing seeding rates and yield per thousand (YPT) steadily decreased with increasing seeding rates (Table 1). YPT is a measure of the yield per thousand plants and can be used as a tool to determine the optimum planting density. Final stand counts were much lower than the respective seeding rates in all treatments with larger differences as seeding rates increased (Figure 1). Relentless rains after planting may have contributed to these lower stand counts. TABLE 1. SEEDING RATE IMPACT ON FINAL STAND COUNT, YIELD, AND YIELD PER THOUSAND PLANTS (YPT) Final Stand (plants/acre) YPT 60,000 47, ,000 73, ,000 95, , , , , , , The field had been previously planted to corn - Page 1 of 6 -

2 Final Stand Count (plants/acre) 300, , , , ,000 50, , , , , , ,000 Figure 1. Seeding rate compared to final stand count at harvest. Seeding Density Final Stand Count The highest yield (92.2 bu/acre) was attained at the seeding rate of 260,000 seeds/acre (Figure 2). s were much higher in 2015 compared to the 2014 trial, possibly due to late-season hail damage that occurred in 2014 (Figures 2 and 3). The most profitable seeding rate (based on revenue seed cost) varied depending on seed costs and fluctuating soybean market prices (Tables 2 through 4). A comparison of soybean plants from the different seeding rates shows that smaller plant stature and limited branching occurs with increased seeding rates (Figures 4 and 5). Takeaways Soybeans can still achieve fair yields at low seeding rates and low final stand counts; however, significant yield was sacrificed at the lowest seeding rate of 60,000 seeds/acre in this study. Soybeans are often seeded at higher rates, which may not provide significant yield or profit increases; however, higher rates may provide a buffer for stand losses that often occur throughout the growing season with weather events common to the High Plains. Soybean seeding rate recommendations vary based on many factors and profitability will ultimately be influenced by seed costs and market prices. Always take into consideration planting date, row spacing, expected emergence, and the yield potential of the field, which includes moisture availability and fertility, when making decisions about soybean seeding rate. Source: 1 Rees, J., Glewen, K., Zoubek, G., and VenDeWalle, B Nebraska on farm research network soybean seeding rate findings. University of Nebraska-Lincoln. Legals The information discussed in this report is from a single site, replicated demonstration. This informational piece is designed to report the results of this demonstration and is not intended to infer any confirmed trends. Please use this information accordingly. Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible. Monsanto and Vine Design is a registered trademark of Monsanto Technology LLC. All other trademarks are the property of their respective owners Monsanto Company CAM - Page 2 of 6 -

3 Average LSD (0.1) = , , , , , ,000 Figure seeding rate impact on soybean yield. 76 Average LSD (0.1) = , , , , , ,000 Figure seeding rate impact on soybean yield. - Page 3 of 6 -

4 TABLE 2. SEEDING RATE ECONOMICS BASED ON A SEED COST OF $45 PER 140,000 SEEDS Seed Cost ($/acre) Revenue Seed Cost ($/acre) $8/bu $9/bu $10/bu $11/bu $12/bu 60, , , , , , , , , , , Revenues based on a seed cost of $45 per unit (1 unit = 140,000 seeds) and varying soybean market values ($8/bu - $12/bu). TABLE 3. SEEDING RATE ECONOMICS BASED ON A SEED COST OF $55 PER 140,000 SEEDS Seed Cost ($/acre) Revenue Seed Cost ($/acre) $8/bu $9/bu $10/bu $11/bu $12/bu 60, , , , , , , , , Revenues based on a seed cost of $55 per unit (1 unit = 140,000 seeds) and varying soybean market values ($8/bu - $12/bu). - Page 4 of 6 -

5 TABLE 4. SEEDING RATE ECONOMICS BASED ON A SEED COST OF $65 PER 140,000 SEEDS Seed Cost ($/acre) Revenue Seed Cost ($/acre) $8/bu $9/bu $10/bu $11/bu $12/bu 60, , , , , , Revenues based on a seed cost of $65 per unit (1 unit = 140,000 seeds) and varying soybean market values ($8/bu - $12/bu). Figure 4. Side-by-side comparison of branching at the different seeding rates (60,000 seeds/acre on the left to 260,000 seeds/acre on the right). - Page 5 of 6 -

6 Figure 5A. 60,000 seeds/acre Figure 5B. 100,000 seeds/acre Figure 5C. 140,000 seeds/acre Figure 5D. 180,000 seeds/acre Figure 5E. 220,000 seeds/acre Figure 5F. 260,000 seeds/acre Figure 5 (A-F). Soybean plants showing differences in branching that can occur at different seeding rates. - Page 6 of 6 -