Figure 2. Urbana plots in mid-September 2010

Planting Date, Row Spacing, and Seeding Rate Effects On Soybean YieldJoshua Vonk, Emerson Nafziger and Vince Davis

Department of Crop Sciences; College of Agricultural , Consumer, and Environmental Sciences; University of Illinois at Urbana-Champaign

IntroductionThe rise in input costs for soybean production, particularly seed costs, increase the need to improve production efficiency. We conducted an experiment in 2010 to compare planting date responses under six combinations of row spacing and seeding rate at six locations throughout Illinois. By examining the interaction among these factors, we hope to help refine recommendations that will enable Illinois soybean producers to maximize profitability.

AcknowledgementsWe thank the Illinois Soybean Association for funding this work. We also thank the farm crew at UI South Farm, Stephen Ebelhar and staff at Dixon Springs Agricultural Center, Lindell Deal at Brownstown, Lyle Paul and Dave Lindgren at DeKalb, Eric Adee and Marty Johnson at Monmouth, and Mike Vose at the Orr Center at Perry.

Experiment Design• Randomized Complete Block (RCB) design with 4

replications• 24 treatments, with complete factorial arrangements of:

• Planting Dates (4): Mid-April, Early-May, Late-May, Early-June

• Seeding Rates (3): 173,000; 297,000; and 420,000 seeds ha-1

• Row Spacing (2): 38 and 76 cm wide rows• Additional Information

• The Dixon Springs plots were planted one to two weeks later and at 25,000 seeds ha-1 more than indicated above.

• Brownstown was limited by wet weather to three planting dates that started around seven weeks late, and at 25,000 seeds ha-1 more than indicated above.

• Locally competitive, mid-range maturity, glyphosate-resistant cultivars were planted.

• Seedbeds were prepared with conventional tillage.

• Preemergence residual herbicide and postemergence glyphosate were used at all locations for weed control.

Conclusions• Due to similarity in responses to treatments over the

four northern locations (Table 1), results from DeKalb, Monmouth, Perry, and Urbana were combined for presentation.

• Overall: The planting date effect on seed yield was significant at all locations with the first date yielding 40% more than the last planting date, and accounted for about 70 % of the variability at all of the locations. Earlier planting resulted in a higher yield (Figure 6) at all locations, with an accelerating decline (quadratic) response to delayed planting except at Dixon Springs, where the decline was linear.

• Brownstown: The very late seeding dates at this locations likely contributed to the large number of significant effects and interactions. Seeding rate effects, while significant, were small. The planting date by row spacing interaction reflected the fact that narrow rows yielded significantly more than wide rows at the first (23% more) and third (23% more), but not at the second, planting date.

• Monmouth: The row spacing by seeding rate interaction was significant, but with no apparent structure: wide rows and the highest seeding rate produce the highest yield (4500 kg ha-1 ), with narrow rows and the middle seeding rate the next-highest (4466 kg ha-1 ).

• Perry: The highest seeding rate yielded significantly greater than the lowest seeding rate, 4231 and 4032 kg ha-1 respectively (5% greater). The middle seeding rate was not different from either the high and or low seeding rate.

• Urbana: Narrow rows yielded significantly more than wide rows, 4652 and 4432 kg ha-1 respectively (5% greater).

• The experiment is being repeated in 2011.

Figure 1a. 38-cm rows, planted April 21

Figure 1b. 38-cm rows, planted June 7

Figure 1c. 76-cm rows, planted April 21

Figure 1d. 76 cm rows, planted June 7

Figure1. Photos taken on July 1st, 2010. All are from the seeding rate of 173,000 seeds ha-1

Table 1. ANOVA Results of Seed Yield For Fixed Effects by Location

Fixed Effects Locations in Illinois

Brownstown DeKalb Dixon Springs Monmouth Perry Urbana

Planting Date (D) *** *** *** *** *** ***

Seeding Rate (S) ** NS† NS NS * NS

Row Spacing (R) *** NS NS NS NS ***

D x S ** NS NS NS NS NS

D x R * NS NS NS NS NS

S x R ** NS NS ** NS NS

D x S x R * NS NS NS NS NS

* Significant at the P = 0.1 probability level.** Significant at the P = 0.05 probability level.*** Significant at the P = 0.001 probability level.† NS = no significant differences at P ≤ 0.1.

10 30 50 70 90 1100

1000

2000

3000

4000

5000

6000

f(x) = − 1.20959496324365 x² + 152.46144736738 x − 1325.5697532908R² = 0.719520082552189

f(x) = − 12.7732762341546 x + 3185.49744677925R² = 0.215995038507714

f(x) = − 0.245910112780079 x² − 1.1754567834525 x + 4843.20506081664R² = 0.478800094446713

Figure 3. Response of Planting Date on Seed Yield at Six Locations Averaged Across Other Fixed Effects

DeKalb Monmouth Perry UrbanaPolynomial (DeKalb Monmouth Perry Urbana)Dixon Springs

Days After April 1st

Yiel

d (k

g/ha

)

April May June July