تعيين حد بحراني عناصر كم مصرف در خاك هاي گندم ديم در شمال غرب ايران

Determination of critical levels of soil micronutrionts for dryland wheat in the North west of Iran

In order to determinate critical levels of Fe, Mn, Zn, Cu and B micronutrients for dryland wheat in Western Azarbayejan, Eastern Azarbayejan, Kurdestan and Kermanshah dryland areas, experiments were conducted using RCBD design with 4 treatments (including control) and three replications for each micronutrients in four years (1998-2002). The total number of sites for Fe, Mn, Zn, Cu and B were 26, 25, 27, 26 and 17, respectively. Fe fertilizer rates were used 0, 5, 10 and 15 kg.ha^-1 from iron chelate (NaFeEDDHA); Mn and Zn fertilizer rates were used , 0, 5, 10 and 15 kg.ha^-1 from Manganese Sulfate and Zinc Sulfate sources, respectively. Cu fertilizer rates were used 0, 2.5, 5 and 7.5 kg.ha^-1 from Copper Sulfate; and B fertilizer rates were used 0, 1.5, 3 and 4.5 kg.ha^-1 from Boric Acid sources. Crop and soil data uniformity were tested for experimental sites. Data were used to fit best models for soil testing data and relative grain yield responses for each micronutrient. Results showed that for cation micronutrients, the best model was Mitshcherlich equation. In this model, Fe, Mn, Zn and Cu the critical levels for obtaining 90% of maximum grain yield were 8.8, 11.3, 0.88 and 1.8 mg.kg^-1 in soil, respectively. For the anion B critical level was determined 0.65 mg.kg^-1in soil. It is concluded that Fe, Mn, Zn, Cu and B, critical levels in soils of drylands in the North-west of Iran can be used to determine research priorities as well as fertilizers management and applications. Key words: Critical level, Micronutrients and dryland wheat.