Iron-deficiency chlorosis (IDC) has been observed in many soybean fields in North Dakota and northwestern Minnesota during the 2017 growing season, according to Hans Kandel, North Dakota State University Extension agronomist.

Soybean IDC is a nutrient deficiency that occurs if soybean plants are unable to take up enough iron, even if sufficient iron is in the soil. Affected plant tissues are yellow with green veins. Yellowing, browning and stunting of the plants during the early vegetative stages will result in reduced soybean yields.

The symptoms usually show early during the growing season when the plants are in the two- to seven-trifoliate leaf stages. Soybean plants may grow out of the IDC symptoms and turn green at the end of the vegetative growth stages.

During the early summer, NDSU researchers tested 241 Roundup Ready and Xtend soybean varieties, as well as 69 conventional and Liberty Link varieties for IDC tolerance. The test results are available at https://www.ag.ndsu.edu/varietytrials/soybean.

The results are based on field studies conducted at four locations with known IDC problems. Visual ratings were made on a 1 to 5 scale, with 1 representing no chlorosis and 5 being the most severe chlorosis. Ratings were taken at multiple growth stages.

Soybean varieties have genetic differences for tolerance to IDC. No soybean variety is immune to chlorosis, but large differences occur between the most tolerant and most susceptible varieties.

“Variety selection is the most important management strategy to reduce IDC expression in the field,” says Ted Helms, NDSU soybean breeder. “This data has been provided to encourage farmers to select IDC-tolerant cultivars for fields that have a past history of IDC.”

The North Dakota Soybean Council provided funding for the studies.

NDSU Agriculture Communication – Aug. 24, 2017