SUMMARY INTRODUCTION

Evaluating soybean plant populations and planting dates in Manitoba.
Cassandra
1Department
1
Tkachuk ,
Yvonne
1
Lawley ,
Michael
2
Ostlie ,
of Plant Science, University of Manitoba, Winnipeg, Manitoba 2Carrington Research Extension Center, North Dakota State University, Carrington, North Dakota
3Department of Soil Science, University of Manitoba, Winnipeg, Manitoba
Cassandra Tkachuk: [email protected] Yvonne Lawley: [email protected]
INTRODUCTION
Soybean production has increased dramatically
in Manitoba over the past decade with 1.35
million acres planted in 2015.1 Currently,
Manitoba farmers are testing different seeding
rates and planting strategies to optimize
soybean production and economic return.
Optimal seeding rates vary among locations,
thus seeding rate research must be validated for
Manitoba specifically. Soybeans also have the
ability to compensate for reduced stands with
additional branches, pods and seed. Due to
these factors, target plant populations may be
higher than necessary and additional seed costs
may potentially offset yield increases.2 Thus,
emphasis should be placed on economic return
of soybeans, rather than yield maximization
alone.
Carman, Manitoba 2014:
(A) Yield Response to Plant Population
RESULTS
Carman, Manitoba 2015:
(D) Yield Response to Plant Population
y=56.66(1-e-0.0294x)
P<0.0001
y=55.43(1-e-0.0286x)
P<0.0001
y=48.79(1-e-0.0204x)
P<0.0001
y=44.87(1-e-0.0175x)
P<0.0001
y=32.90(1-e-0.0366x)
P<0.0001
(B) Revenue and Cost
(E) Revenue and Cost
(C) Marginal Revenue and Marginal Cost
(F) Marginal Revenue and Marginal Cost
OBJECTIVES
1. Quantify the relationship between soybean
plant population and yield in Manitoba.
2. Determine the economic optimum seeding
rate for different planting windows in
Manitoba.
MATERIALS & METHODS
• Two field sites in 2014 and 2015: (1) Ian N.
Morrison Research Farm in Carman,
Manitoba, (2) Carrington Research Extension
Center in Carrington, North Dakota.
Carrington data not shown.
• Split plot experimental design with 4
replicates:
• Planting dates at Carman in 2014: ideal (May
26) and late (June 9).
• Planting dates at Carman in 2015: early (May
4), ideal (May 22), and late (June 10).
• Six target plant populations: 80,000 to
230,000 plants ac-1.
• Plot sizes: 8 m long x 2 m wide.
• Seeder: Disk drill with 14” row spacing.
• Variety: Dekalb 24-10RY.
• Seeding rates were adjusted for 20% mortality
and 95% germination.
• Inputs: Fungicide seed treatment, liquid and
granular inoculant.
www.PosterPresentations.com
SUMMARY
• Yield increased exponentially with increasing
plant population until a yield plateau was
reached for each site year (Figures 1A and 2D).
• Yield plateaus ranged from 49 to 57 bu ac-1 for
early-ideal planting dates (Figures 1A and 2D).
• Yield plateaus ranged from 33 to 45 bu ac-1 for
late planting dates (Figures 1A and 2D).
• Contrasting trends between 2014 and 2015
were observed for economic optimum plant
populations calculated from early to ideal, and
late planting dates (Figures 1C and 2F, Table 1).
• Carman 2014 results suggest that it was more
economical to reduce seeding rates for later
planting (Figure 1C, Table 1), whereas Carman
2015 results support the practice of increasing
seeding rates with later planting (Figure 2F,
Table 1).
• Other agronomic factors, such as weed
competition, should also be considered when
selecting seeding rates to mitigate risk but
were beyond the scope of this project.
Figure 3. Plant population and planting date experiment at
Carman on September 4, 2015.
o Main Plot – Planting Date
o Sub Plot – Target Plant Populations
RESEARCH POSTER PRESENTATION DESIGN © 2012
Francis
3
Zvomuya
Figure 1. (A) Soybean yield response to plant population,
Figure 2. (D) Soybean yield response to plant population, (E)
(B) soybean revenue and seed cost functions, and (C)
soybean revenue and seed cost functions, and (F) marginal
marginal revenue and marginal cost functions for ideal and
revenue and marginal cost functions for early, ideal, and late
late planting dates at Carman in 2014.
planting dates at Carman in 2015.
Table 1. Average soybean seed mortality and economic optimum plant
ECONOMIC ASSUMPTIONS
populations for different planting windows at Carman, Manitoba.
• Commercial soybean price of
$10 bu ac-1.3
• Soybean seed cost of $0.36
1000 seeds-1 ($50 unit-1).3
• Average soybean seed mortality
for each planting date (Table 1).
NEXT STEPS
• Sensitivity analysis of economic assumptions.
• Evaluate seeding rates and planting dates in
new soybean production areas of Manitoba.
• Evaluate for new, early-maturing varieties.
ACKNOWLEDGEMENTS
REFERENCES
1Manitoba
Pulse & Soybean Growers:
http://www.manitobapulse.ca/pulses-in-manitoba/
2De Bruin, J.L. and Pederson, P. 2008. Seed yield response
to planting date and seeding rate in the Upper Midwest.
Agron. J. 100(3):696-703.
3Dennis Lange, Manitoba Agriculture Food and Rural
Development: Personal Communication.