As planting decisions are finalized, the risk of iron deficiency chlorosis (IDC) is one of the factors soybean growers in Western Canada and the Northern Plains are keeping in mind after unprecedented yellowing due to IDC in many areas last year.
A wet 2016 growing season followed by a dry start to 2017, left elevated soluble salt levels near the soil surface, contributing to the problems with IDC last year. Most of the plants in those yellow patches recovered, but the hardest hit spots turned necrotic and died, hurting overall yields.
In many cases, the salts or carbonates that caused IDC in 2017 are still there heading into 2018.
“Many people haven’t tested for carbonates in the past because it’s not a nutrient, and if you haven’t planted soybeans before, there was no reason to test for carbonates,” says John Lee of AgVise Laboratories in this Soybean School video, referring to the expansion of soybean acres on the prairies in recent years.
When interpreting soil test results, research at the University of North Dakota has shown that high carbonates (>5.0%), along with high salts (>1.0 mmhos/cm), creates a high risk of iron chlorosis.
“Once they have that information, along with salinity, they can make educated decisions as to where the beans go, the risk of iron chlorosis, where they should put tolerant varieties, and where they can put varieties that don’t need that IDC tolerance that are racehorse varieties,” notes Lee.
Early rains could also mitigate some of the IDC risk by moving salts back out of the root zone, he notes.
Lee joined Kelvin Heppner at CropConnect in Winnipeg to discuss what the North Dakota-based soil testing lab is finding on soil tests heading into 2018, including trends with potassium and phosphate levels as soybean acres have grown: