What is causing striped corn? Part 2

Soil and leaf tissue tests suggest magnesium deficiency and, to a lesser extent, sulfur were causing leaf striping on corn.

In 2015, several growers in Ingham County, Michigan, experienced excessive leaf striping, or interveinal chlorosis, on corn (see Part 1). A certain amount of leaf striping in new growth is noticeable every year. This year, the symptoms were widespread over many acres and fields. Striped areas were sometimes interspersed with patches or rows of almost normal looking corn. Corn was at the V5-V6 growth stage.

Scientific literature suggested that corn striping can be caused by several nutrient deficiencies. These nutrients included magnesium (Mg), sulfur (S), zinc (Zn) and manganese (Mn). Non-nutrient factors are also implicated, such as herbicide injury, root damage, cold temperature, corn genetics, soil pH and soil type. With no clear cut evidence, there has been much speculation as to what is causing these symptoms.

To diagnose if this condition was caused by a nutrient deficiency, Michigan State University Extension analyzed soil and leaf tissue representing good versus striped areas of the field. These tests included most of the essential plant nutrients, but only the nutrients that were of interest to this study are featured in Tables 1 and 2.

Table 1. Soil test data for “good” versus “striped” areas of corn in 2015

Soil test

Good area

Stripped area

pH

6.8

5.5 (low)

Organic matter %

3.3

2.0

Mg, ppm

63 (optimum)

35 (below optimum)

S, ppm

8 (low)

7 (low)

CEC, meq/100g

6.1

3.8

Lime requirement (t/A)

0

2.0 (dolomitic lime)

 

Table 2. Leaf tissue analysis for “good” versus “striped” areas of corn in 2015

 

Nutrient

 

Good area

 

Striped area

 

Sufficiency range

N %

3.42

4.87

3.00-3.50

Mg %

0.21

0.10

0.13-0.30

S %

0.17

0.17

0.15-0.50

Mn, ppm

62

537

15-300

Zn, ppm

28

40

15-60

N:S ratio

20.1

29:1

15:1-201:1

Soil test data indicated the soil in the striped area was lower in organic matter, cation exchange capacity and pH compared to good area. The striped area had below optimum Mg levels in soil. Sulfur levels were considered low in both areas, even though the soil test is not a reliable indicator for S.

Leaf tissue analysis indicated Mg uptake was below the sufficiency range in the striped area compared to the good area. The S uptake was identical in both areas, but at the lower end of the sufficiency range. The nitrogen to sulfur ratio in the stripped area was 29:1, indicating an imbalance and a greater likelihood of S deficiency in the leaf tissue. The uptake levels of other two nutrients, Zn and Mn, was in the sufficiency range.

This study was limited in that only one composite soil and tissue sample representing good and striped areas of the field was analyzed. However, soil and leaf tissue tests pointed toward Mg deficiency and, to a lesser extent, S deficiency as causing the leaf striping on corn.

Magnesium deficiency in low pH and coarse-textured soils is a concern in southwest Michigan. In this instance, the soil test recommendation for the striped area was 2 tons per acre dolomitic lime. These fields will benefit from a variable rate fertilizer and lime application program. A rescue application of 20 pounds of Mg sulfate (Epsom salts) as a foliar spray was ruled out this year because of excess rain and soggy field conditions throughout June and early July.

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