Grain Sorghum Management under Limited Irrigation
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Risk Management in Sorghum
• Important Decisions
– Hybrid selection
– Planting
date/Maturity
– Water supply
– Seeding rate
– Weed control
– Soil Fertility
– Pest Management
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Limited Irrigation Goals
• Allocate limited resources to maximize returns
– Drought tolerant crops?
• Wheat or sorghum?
– Cropping system on the acre?
• Irrigated / Dryland crop mixture
– Critical growth stages?
• Not every inch of irrigation is equal when it comes to timing.
3
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Drought Tolerant Crops?
-50
0
50
100
150
200
4.0 8.0 12.0 16.0 20.0 24.0 28.0
Water Use (in)
Gra
in Y
ield
(b
u/a
)
Grain Sorghum - 9 bu/in
Soybean - 5.2 bu/in
Corn - 11 bu/in
Wheat - 6.5 bu/in
L.R. Stone
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Environments with a wide range of water
Years
1992 through 2011
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Sorghum and Corn Yields
0
50
100
150
200
250
300
0 50 100 150 200 250 300
So
rgh
um
Yie
ld, b
u/a
Corn Yield, bu/a
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7SC Kansas Rainfed
Category Corn Sorghum
Yield (bu/acre) 110 110
Price per bu 5.68 5.58
Gov’t Payment 16.58 16.58
Total Revenue 641.38 630.39
Seed 66.47 12.58
Herbicides 28.16 18.48
Insect/Fungicides 1.00 0.00
Fertilizer 85.00 94.20
Consult/Dry/Ins. 0.00 0.00
Machinery 116.76 114.02
Non Machinery
Labor
13.19 12.88
Land Rent 74.40 74.40
Total 391.54 332.31
Return over Costs 249.84 298.07
NE Kansas Rainfed
Category Corn Sorghum
Yield (bu/acre) 160 130
Price per bu 5.68 5.58
Gov’t Payment 14.68 14.68
Total Revenue 923.49 740.09
Seed 87.48 16.01
Herbicides 30.00 30.58
Insect/Fungicides 26.55 0.00
Fertilizer 110.56 72.80
Consult/Dry/Ins. 17.29 11.70
Machinery 98.86 87.02
Non Machinery
Labor
11.17 9.83
Land Rent 136.80 136.80
Total 527.46 372.99
Return over Costs 396.03 367.10
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Economic Comparison
-800
-600
-400
-200
0
200
400
600
800
1000
0 50 100 150 200 250 300
So
rgh
um
Ad
van
tag
e,
$/a
Corn Yield, bu/a
Sorghum/Corn Price Ratio: 93% 100%
Corn yields where
Economic Tipping Point = 110 132 bu/a
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Total Leaf Area
60% D.M & 70 % N
Maximum Root Depth
Panicle Differentiation
Potential Seed Number
Determined
6 32-35 32-35 32-35 15
Plant EmergePanicle
Initiation
BootPhys
Mat.Harv
GSI GSII GSIII
Total Leaf
Number
1/3 Leaf Area
1/5 Total Wt.
~ 8 Leaf Stage
Total Dry Wt.
Total Grain Wt.
Loss of Leaf
Area
Sorghum Growth, Development, and Yield
AnthesisSeed Set
Final Seed Number Set
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Seed Number per Acre and Yield
y = 1.0546x - 1.4332
R2 = 0.9143
0
20
40
60
80
100
120
0 20 40 60 80 100 120
Seed/a (millions)
Yie
ld (
bu
/a)
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Limited Irrigation Sorghum Management
• Planting Date: Plant early
– You want the longest growing season you can get and
there is often little or now penalty for planting a bit early
• Hybrid Maturity: Fullest for your area
– NW KS = Medium
– SW KS = Medium Full
• Planting Rate: 70,000 seed per acre (or more)
• Row Spacing: Narrow rows might improve yields
– Never saw lower yields in narrow rows in previous studies
– Stand establishment with drills may be a challenge
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60
80
100
120
140
160
10-May 30-May 16-Jun 30-Jun
Planting Date
Yie
ld (
bu
/A)
Early Medium Full
Sorghum Planting Date – NC Kansas
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Limited Irrigation Sorghum Management
• Planting Date: Plant early
– You want the longest growing season you can get and
there is often little or now penalty for planting a bit early
• Hybrid Maturity: Fullest for your area
– NW KS = Medium
– SW KS = Medium Full
• Planting Rate: 70,000 seed per acre (or more)
• Row Spacing: Narrow rows might improve yields
– Never saw lower yields in narrow rows in previous studies
– Stand establishment with drills may be a challenge
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14
60
80
100
120
140
160
5 10 15 20 25 30 35
Row Spacing (in)
Yie
ld (
bu
/a)
Man-95 Pow-95
Bel-95 Man-96
Bel-96
LSD = 10.4
Sorghum Row Spacing
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Deficit Irrigation – Bushland, TX
Variable Full Irr.
50%
Deficit
Irr.
Rainfall (in) 8.3 8.3
Irrigation (in) 14.5 6.7
Total Water (in) 22.8 15.0
Crop Water
Use (in) 24.4 22.0
Yield (bu/acre) 150.2 146.5
WUE (bu/in) 5.9 6.6
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1.3
Feet
2.6
3.9
5.2
6.6
7.9
0.0
1.3
Feet
2.6
3.9
5.2
6.6
7.9
0.0
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Sorghum and Soil Moisture(Tribune, KS 1973-1987)
y = 5.0465x + 27.862
0
20
40
60
80
100
120
0 2 4 6 8 10 12
Soil Moisture at Planting (in)
So
rgh
um
Yie
ld (
bu
/a)
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Irrigation Effects on Grain Sorghum Hybrids
Treatment Medium Early Full Season
Yield, bu/acre
Dryland 110 95
Boot 149 160
Mid-bloom 135 148
Boot +Mid-
bloom
162 176
Hybrid Avg 139 145
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Irrigation Timing and Grain Sorghum
Time of Irrigation Yield
bu/a
Preplant only 65
Pre+Boot Stage 125
Pre+Half-Bloom 115
Pre+Soft-Dough 114
Full Season Irrigation 126
Tribune, KS
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Limited Irrigation
Tribune, KS
Irrigation
Amount Corn
Grain
Sorghum Soybean Sunflower *
(in) - - - - - - - - bu/a - - - - - - - - lb/a
5 124 124 34 1725
10 169 (36) 149 (20) 41 (20) 1978
15 184 (48) 172 (39) 47 (39) 1759
() represent % increase over 5 in irrigation
* Stem borer infestation lowered sunflower yields
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Stalk rots
• Stalk Rots in Corn and Sorghum
(KSU Pub No. L-741)
– Stalk rot is the most prevalent
disease of corn and sorghum in
Kansas. Annual losses are difficult
to determine, because unless
lodging occurs, the disease goes
mostly unnoticed. The best
estimates are that at least 5
percent of the corn and sorghum
crop are lost each year to stalk rot.
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Stalk Rots
• Prevention– Reduce stress through late
season irrigation
– Harvest Early
– Select hybrids that have good standability ratings
– Select hybrids with the stay-green trait
– Balanced N program (avoid too much or too little)
– Maintain adequate K and Cl levels in system
– Rotate to small grains or alfalfa
• Types
– Fusarium
• Dry early and warm, wet
weather after anthesis
– Charcola Rot
• High soil temperatures
and low soil moisture
during grain fill
– Anthrachnose
• High temperatures and
humidity
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Summary
• Consider crop mixtures or cropping systems that return the greatest $/acre. It could be that some crops get very little irrigation water.
• Plant sorghum as early as possible and potentially in narrow rows to maximize yields under limited irrigation.
• Be certain to reduce plant water stress during GS II when the panicle is developing.
• Water during grain fill will improve yields slightly, but will result in better stalk quality and less lodgeing.
• Manage lodging through hybrid selection, proper fertility and appropriate crop rotations.
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• Questions?
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