Benson Iron Chlorosis

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					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. 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.

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3.

4.

5.

25 20 15
10 25

Plant Ht. (inches) CCE (%)
7.9 5.4 6 0.7 8

10 5
0.4

Salts (mmhos/cm) pH

0 Healthy Severe
Soybean Iron Chlorosis Project Summer 2001: Agvise @ Benson, MN Fields Sampled: 79 Locations: 76 from S. MN, 3 from SD

16 14 12 10 8 6 4 2 0 Healthy Severe
Soybean Iron Chlorosis Project Summer 2001: Agvise @ Northwood, ND Fields Sampled: 26 Locations: 15 ND, 7 MN, 3 SD
1.9 0.4 1 8 7.5 5.7 8 16

Plant Ht. (inches) CCE (%) Salts (mmhos/cm) pH

Average Plant Height at Sampling Time
25 20 15 10 5 6 0 Healthy Severe Height (inches) 25

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 10 8 6 4 2 0 Healthy Severe 7.5 16.4 Height (inches)

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 0.3 0.2 0.1 0 Healthy Severe 0.4 0.7 Salts

Soybean Iron Chlorosis Project Summer 2001: AGVISE @ Benson, MN Fields Sampled: 79 Locations: 76 from S. MN, 3 from SD

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%

8% 24% 33% 6%

3%

3%

13% 56% 26%

2%

11%
3%

35%
12%

3%

% 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%

62%

25%

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.


				
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