**3.1 Roundup ready vs conventional cultivars**

As Roundup Ready™ (RR) cultivars were first being released there was local concern among growers and crop consultants that resistance to Fe deficiency may not have been incorporated during development of earlier releases. During 2002, ten RR™ and ten 'conventional' cultivars were grown at two rates of Fe-EDDHA (0 and 8.96 kg ha-1) at the University of Minnesota Northwest Research and Outreach Center (NWROC) on soils with a known history of mild to severe Fe deficiency. A relatively high rate of application of Fe-EDDHA increased relative chlorophyll readings at V3 about 13% (4.6 SPAD units) and increased grain yield nearly 18% (434 kg ha-1). Roundup Ready cultivars out-yielded conventional cultivars by approximately the same amount, 19% (453 kg ha-1). Nonetheless, seed [Fe] at harvest did not differ between Fe-EDDHA rates, nor between RR and conventional cultivars (Table 3). Seed [Fe] at harvest was moderately related to both published visual chlorosis score (r2=0.452) and Fe concentration of the seed used for planting (r2=0.458). Classifying cultivars on the basis of their published VCS and then their planting seed [Fe] resulted in the same cultivars being in each class and, consequently, having the same r2 values. This research involved a relatively small sample of cultivars grown under harsh conditions and may not have fairly represented the importance of Fe 1000-1 seeds, seed [Fe], and/or Fe removal. Similarly, it is important to remember that these results cannot be extended to all RR and conventional soybean cultivars.
