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July 1, 2016 – June 30, 2017 Annual Report: Visual ratings for iron-deficiency chlorosis

Principal Investigator: Dr. Ted Helms, Department of Plant Sciences, North Dakota State University

Iron is less available to the soybean plant on high pH soils. The symptoms of iron-deficiency chlorosis (IDC) include leaves that are yellow in June and sometimes through July. Soybean growers with fields that have a past history of IDC need information to aid them in comparing varieties from many different companies in side-by-side comparisons. There are genetic differences among cultivars for tolerance to IDC. Even a small amount of yellowing in the soybean leaves can reduce final yield by twenty percent. We measure the tolerance to IDC by the amount of yellowing in the leaves. For fields with IDC, visual yellowing has been shown to be closely correlated to yield. This data provides unbiased information that enables growers to choose the best variety for their IDC prone fields.

The objective was to screen all private company varieties that have been entered into the Langdon Research and Extension Center (REC), Carrington REC, Minot REC, Williston REC and Fargo Main Station yield trials for visual ratings of IDC at multiple field locations with a past history of IDC symptoms. A second objective is to provide visual IDC screening of advanced NDSU breeding lines. Comparing soybean varieties from different companies requires that all varieties be evaluated in side by side comparisons in the same field. Otherwise, a fair comparison is not possible.

In 2016, four locations on farmer-cooperator fields with a past history of IDC symptoms had been identified and were later planted with hill-plots. There were 232 Roundup Ready company varieties tested and 72 Liberty Link and non-GMO company varieties tested. Also, the NDSU soybean breeder evaluated 116 advanced NDSU breeding lines for visual IDC symptoms. Those locations included Leonard, Eire, Colfax and Galesburg, ND. A total of 6,720 hill-plots were planted. Data was analyzed and reported in the NDSU bulletin entitled ‘North Dakota Soybean Performance’ and was posted online.

This is the largest data set with the most comparisons of many different company varieties, both Roundup Ready, Liberty Link and non-GMO for North Dakota and western Minnesota. Because 2016 data is averaged across four locations with four replications per location, the data is quite reliable in aiding growers to select the best varieties for their IDC prone fields. This data enables growers to increase their yield on their IDC prone fields because those varieties with the least amount of yellow IDC symptoms will yield the best on those fields that have that problem.