Soybean Iron Chlorosis Project
2001
Summary Report
AGVISE Laboratories
Benson, MN & Northwood, ND
Soybean Iron Chlorosis Project
Overview
In cooperation with many of our
customers, AGVISE Laboratories
conducted a soybean iron chlorosis
project in the summer of 2001 throughout
the tri-state areas of MN, ND and SD.
Sample locations were selected based
upon chlorosis hot spots in grower fields
throughout the region. Three soil
samples were collected in each field,
representing normal (healthy) soybean
growth, moderately affected areas and a
severely affected area. Only the severe
and normal areas will be compared in
this summary. Lab analysis consisted of
measuring soil pH, carbonates and
soluble salts. Field information included
location, variety, plant height at time of
sampling, date sampled, crop color,
presence or absence of SCN on roots
and row spacing. This summary will only
look at plant height, pH, soluble salts and
carbonates.
Summary
1.
2.
3.
4.
5.
Plant Height: Dramatic
difference between chlorotic
and healthy areas.
Soil pH: No difference
between chlorotic and healthy
areas.
Soluble Salts: Major factor in
contributing to soybean iron
chlorosis.
Carbonates: Major factor in
contributing to soybean iron
chlorosis.
Note: SCN was a non-factor in
the vast majority of fields
sampled.
25
20
25
Plant Ht.
(inches)
CCE (%)
15
10
10
8
7.9
5.4
6
5
0.4
0.7
Healthy
Severe
0
Soybean Iron Chlorosis Project
Summer 2001: Agvise @ Benson, MN
Fields Sampled: 79
Locations: 76 from S. MN, 3 from SD
Salts
(mmhos/cm)
pH
16
14
16
12
10
8
8
8
7.5
5.7
6
4
2
1.9
0.4
1
0
Healthy
Severe
Soybean Iron Chlorosis Project
Summer 2001: Agvise @ Northwood, ND
Fields Sampled: 26
Locations: 15 ND, 7 MN, 3 SD
Plant Ht.
(inches)
CCE (%)
Salts
(mmhos/cm)
pH
Average Plant Height
at Sampling Time
25
20
25
15
Height (inches)
10
5
6
0
Healthy
Severe
Soybean Iron Chlorosis Project
Summer 2001: AGVISE @ Benson, MN
Fields Sampled: 79
Locations: 76 from S. MN, 3 from SD
Average Plant Height
at Sampling Time
18
16
14
12
16.4
10
8
Height (inches)
6
4
7.5
2
0
Healthy
Severe
Soybean Iron Chlorosis Project
Summer 2001: AGVISE @ Northwood, ND
Fields Sampled: 26
Locations: 15 ND, 7 MN, 3 SD
Average Carbonate (CCE)
10
9
8
7
6
5
4
3
2
1
0
10
CCE (%)
5.4
Healthy
Severe
Soybean Iron Chlorosis Project
Summer 2001: AGVISE @ Benson, MN
Fields Sampled: 79
Locations: 76 from S. MN, 3 from SD
Average Carbonate (CCE)
10
9
8
7
6
5
4
3
2
1
0
CCE (%)
5.7
1.9
Healthy
Severe
Soybean Iron Chlorosis Project
Summer 2001: AGVISE @ Northwood, ND
Fields Sampled: 26
Locations: 15 ND, 7 MN, 3 SD
Average Soluble Salts
0.7
0.6
0.5
0.4
0.7
Salts
0.3
0.2
0.4
0.1
0
Healthy
Soybean Iron Chlorosis Project
Summer 2001: AGVISE @ Benson, MN
Fields Sampled: 79
Locations: 76 from S. MN, 3 from SD
Severe
Average Soluble Salts
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
Salts
0.4
Healthy
Severe
Soybean Iron Chlorosis Project
Summer 2001: AGVISE @ Northwood, ND
Fields Sampled: 26
Locations: 15 ND, 7 MN, 3 SD
Average pH
8
8
7.9
7.5
pH
7
Healthy
Severe
Soybean Iron Chlorosis Project
Summer 2001: AGVISE @ Benson, MN
Fields Sampled: 79
Locations: 76 from S. MN, 3 from SD
Average pH
8
8
8
7.5
pH
7
Healthy
Severe
Soybean Iron Chlorosis Project
Summer 2001: AGVISE @ Northwood, ND
Fields Sampled: 26
Locations: 15 ND, 7 MN, 3 SD
Summary of the 2001
Soybean Iron Chlorosis Project
AGVISE Labs, Benson, MN
• Fields Sampled: 79
– 76 from Southern Minnesota
– 3 from South Dakota
• Plant Height Averages
– Severe Chlorosis: 6 inches
– Healthy:
25 inches
Summary of the 2001
Soybean Iron Chlorosis Project
AGVISE Labs, Northwood, ND
• Fields Sampled: 26
– 15 from North Dakota
– 7 from Northwest Minnesota
– 3 from South Dakota
• Plant Height Averages
– Severe Chlorosis: 7.5 inches
– Healthy:
16.4 inches
Summary of the 2001
Soybean Iron Chlorosis Project
AGVISE Labs, Benson, MN
• pH:
– Severe Chlorosis:
– Healthy:
8.0
7.9
• Range of pH’s
– Severe Chlorosis:
– Healthy:
7.5 to 8.4
6.5 to 8.4
Summary of the 2001
Soybean Iron Chlorosis Project
AGVISE Labs, Northwood, ND
• pH:
– Severe Chlorosis:
– Healthy:
8.0
8.0
• Range of pH’s
– Severe Chlorosis:
– Healthy:
7.9 to 8.3
6.8 to 8.3
Summary of the 2001
Soybean Iron Chlorosis Project
AGVISE Labs, Benson, MN
• Soluble Salts
– Severe Chlorosis: 0.7 mmhos/cm
– Healthy:
0.4 mmhos/cm
• Range of Salts
– Severe Chlorosis: 0 – 3.4 mmhos/cm
– Healthy:
0 – 1.7 mmhos/cm
Summary of the 2001
Soybean Iron Chlorosis Project
AGVISE Labs, Northwood, ND
• Soluble Salts
– Severe Chlorosis: 1.0 mmhos/cm
– Healthy:
0.4 mmhos/cm
• Range of Salts
– Severe Chlorosis: .30 – 2.45 mmhos/cm
– Healthy:
0.1 – 0.9 mmhos/cm
Summary of the 2001
Soybean Iron Chlorosis Project
AGVISE Labs, Benson, MN
• Carbonates (CCE)
– Severe Chlorosis:
– Healthy:
10%
5.4%
• Range of Carbonates
– Severe Chlorosis:
– Healthy:
0.1 – 21%
0 – 20.5%
Summary of the 2001
Soybean Iron Chlorosis Project
AGVISE Labs, Northwood, ND
• Carbonates (CCE)
– Severe Chlorosis:
– Healthy:
5.7%
1.9%
• Range of Carbonates
– Severe Chlorosis:
– Healthy:
0.4 – 13%
0 – 11.7%
Summary of the 2001
Soybean Iron Chlorosis Project
AGVISE Labs, Benson, MN
Locations by County
•
•
•
•
•
•
•
•
•
•
Blue Earth
Brookings (SD)
Brown (SD)
Chippewa
Cottonwood
Douglas
Grant
Kandiyohi
Lyon
Nicollet
•
•
•
•
•
•
•
•
•
Ottertail
Pope
Renville
Sibley
Stearns
Stevens
Swift
Traverse
Yellow Medicine
% of Samples With Carbonates >5.0%
(8600 Samples Tested in Highlighted Areas, Fall 2001)
2%
3%
3%
3%
8% 24% 33%
6%
2%
3%
13% 56%
26%
11%
35%
3%
12%
% of Soil Samples With Soil pH >7.3
(97,000 samples tested for pH in highlighted areas)
70% 54% 77% 80% 97%
57% 32% 44% 69% 92%
40%
20% 28%
25%
62%
18% 16%
Interpretation for Carbonates & Salts
“Higher Salt Level”
• Point Samples
– If salts is higher than 0.7 and carbonate is higher
than 5.0%, severe chlorosis is likely in that point.
• Composite Field Sample
– If salts are higher than 0.4 - 0.7 and carbonate is
higher than 2.5-3.0%, areas of the field are likely
to have chlorosis.
Interpretation for Carbonates & Salts
“Low Salt Levels”
• Point Samples
– If salts is less than 0.4 and carbonate is higher
than 8.0%, chlorosis is likely at that point.
• Composite Field Sample
– If salts are less than 0.4 and carbonate is higher
than 5.0%, areas of the field are likely to have
chlorosis.
Future of Carbonate and Salt Soil Test
•Seed companies testing their variety plots
•Varieties rated by carbonates & salts
•Information used for better management
•Diagnostic tool to investigate spots in fields
•Variety selection
Factors “Known” to Increase Potential
for Iron Chlorosis
•Soluble Salts
•Carbonates
•Excessive water
•Cool Temperatures
•High pH???????
Iron Chlorosis Facts
• Carbonates and Salts are two important
factors affecting potential for iron chlorosis.
• Carbonates are a fixed soil property
• Salts can be reduced with drainage
• Soil pH is not a good indicator of potential iron
chlorosis.
• Knowing the carbonate and salt level can help
growers choose fields to plant soybeans.
• Knowing the carbonate and salt level can help
explain problem areas.