Critical levles and classification of Fe, Mn, Zn, Cu and B were investigated by using Cate-Nelson ANOVA two and three class models for dry land wheat in soils of Western Azarbayejan, Eastern Azarbayejan, Kurdestan and Kermanshah dry land areas. In order to do this study, experiments were conducted in RCBD design with 4 treatments for each micronutrient with three replications for four years (1998-2002). Fe fertilizer rates were 0, 5, 10 and 15 kg.ha-1 from iron chelate (NaFeEDDHA); Mn fertilizer 0, 5, 10 and 15 kg.ha-1 from manganese sulfate; Zn fertilizer rates 0, 5, 10 and 15 kg.ha-1 from zinc sulfate and Cu fertilizer rates 0, 2.5, 5 and 7.5 kg.ha-1 from copper sulfate sources. The determined data were used in Cate-Nelson ANOVA two and three classes models. The results for critical levels by Cate- Nelson 2 classes model for Fe, Mn, Zn and Cu were 8.5, 8, 0.55 and 1.65 mg.kg-1 respectively. Similarly, classification were determined by Cate- Nelson three (low, medium and high) classes ANOVA models for aforementioned micronutrients. Boundaries between low with medium and mediums with high classes were determined for Fe 7.5 and 9.5, Mn 8 and 11, Zn 0.45 and 0.65 and Cu 1.2 and 1.65 mg.kg-1. The results of two and three classes Cate –Nelson ANOVA models were also compared with each other for the relationship between micronutrient and growth response. From the results, it can be concluded critical levels for micronutrients are differed at Cate- Nelson two and three classes models or ANOVA model. From the comparison of two models, the suitable model for determination of critical levels was three classes model.
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