Iron deficiency chlorosis is a destructive physiological disorder of soybeans, which leads to yellowing, stunted plants and reduced yields.

""There is no harmless level of chlorosis,"" says R. Jay Goos, North Dakota State University soil science professor.""Even a temporary yellowing can reduce yield.""

Chlorosis is a problem normally associated with poorly drained soils. These are the soils that most commonly produce yellow soybean plants. Chlorosis also is intensified by wet conditions, salinity and excess nitrate in the soil.

""The most important control measure for chlorosis is variety selection,"" Goos says. ""Fields that produce chlorosis should be planted to a chlorosis-resistant variety. Planting in wider rows, instead of solid-seeding, and using the chelate FeEDDHA also can help, but these control measures cannot replace the use of a resistant variety."

Since 2001, Goos has led a research project devoted to field screening of soybean varieties for chlorosis resistance.

""Because of the destructive nature of chlorosis, it is important that North Dakota farmers have the best possible information on the varieties they grow,” Goos says. “Every seed company conducts its own chlorosis studies and many different rating scales are used. Our trials compare entries from a large number of seed companies. The data NDSU provides allow farmers to find the most resistant varieties using direct, side-by-side comparisons.""

The chlorosis studies for 2007 were conducted at five field locations in eastern North Dakota and were sponsored by the North Dakota Soybean Council and participating seed companies. The results of the studies for 2007 and prior years are available at http://www.yellowsoybeans.com.

NDSU Agriculture Communication