Managing grain sorghum growth and development
through plant population and tiller development.
Tucker Cogburn and Josh Lofton
Department of Plant and Soil Science
Oklahoma State University, Stillwater, OK
• Evaluate seeding rate and how it effects the
emergence, growth, and canopy coverage of
grain sorghum.
• Determining if tillering influences growth of
the plant.
EXPERIMENTAL DESIGN:
• Grain sorghum seeding population and
growth pattern was evaluated in this project.
• Sorghum seeding populations included:
87,500; 137,500; and 187,500 seeds/ha.
• Two growth patterns included: allowing the
sorghum plant to tiller, removing tillers at
formation.
• Sorghum plants were planted in a 76 cm pot
with Chromatin 73B12.
• Pots were maintained in a well watered
condition throughout the experiment.
• After establishment, plant height (cm) and
canopy cover (%) using the Canopeo® app
was determined weekly.
• Tillers were removed manually once emerged
from the soil.
• When tillers were allowed to grow, height
was solely taken on main stem.
30.0
30
25.0
Canopy coverage (%)
35
25
20
15
10
20.0
15.0
10.0
5
5.0
0
0.0
Week 1 Week 2 Week 3 Week 4 Week 5
87,500
137,500
187,500
Week 1 Week 2 Week 3 Week 4 Week 5
87,500
137,500
187,500
Figure 2. Plant height and canola coverage as affected by three plant populations and thinning of sorghum tillers.
70.0
60.0
60.0
50.0
Canopy coverage (%)
OBJECTIVES:
Figure 1. Plant height and canopy coverage as affected by three plant populations and no thinned tiller production
Plant height (cm)
• Grain sorghum is a critical crop for Oklahoma
agriculture.
• Due to the very diverse environmental
conditions experienced in common sorghum
production areas, many agronomic practices
vary from region to region.
• Planting practices, specifically seeding rate,
are one of the more important practices that
shift between production regions.
• Planting sorghum at lower populations allow
the crop to withstand stressful conditions but
also tiller when adequate resources are
present.
• There is a theory that when sorghum tillers, it
can never reach 100% yield potential, due to
splitting of resources.
Plant height (cm)
INTRODUCTION:
RESULTS:
50.0
40.0
30.0
20.0
40.0
30.0
20.0
10.0
10.0
0.0
0.0
Week 1 Week 2 Week 3 Week 4 Week 5
87,500
137,500
187,500
Week 1 Week 2 Week 3 Week 4 Week 5
87,500
137,500
187,500
Results:
• Where sorghum plants were not thinned, higher plant populations resulted in increased plant
height and greater canopy cover. This was potentially due to increased inter-row competition
between the plants.
• Lower population, especially in the 87,500 planting rate, had increased tiller production compared
to the other two populations.
• Removing tillers resulted in drastically increased plant height but inconsistent canopy development.
Conclusions:
• Both plant populations and tiller production affected grain sorghum growth and development;
where the lack of tillers did decrease the growth of the plant but canopy coverage is unclear.