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In order to determine critical macro and micro nutrients norms in orange orchards (Thomson navel and Valencia cultivars) in two main regions (south of Fars and East of Mazandaran) a study was conducted in two years. 40 orange orchards were selected in each region and 30 trees were selected in each orchard. In first yar, soil test and leaf sample were taken from orchards and 10 orchards randomly fertilized based on soil test and leaf analysis. Leaf nutrients concentration were measured and average yields were calculated for each orchard. The compositional nutrients diagnosis (CND) was used to devide high and low yielding orchard groups and critical nutrients norms were calculated for both regions. In south of Fars region, the optimum yield was obtained 33.5MT per ha for Valencia orange orchard and related norms were N= 3.0, P= 0.17, K= 1.37, Ca= 3.3, Mg= 0.36 percent and for Mn= 24, Zn= 17.5, Fe= 75.5, Cu= 8 and B= 76 mg kg-1 dw. Data showed differences between low and high yield orchards is due to boron concentration in the plants where increasing of boron in the leaves resulted in low yield. 62% of orchards had higher than 76 ppm boron in the leaf. 68% of orchards showed N deficiency, 52% of them showed Ca deficiency and 39% of them showed Mn deficiency according to CND norms respectively. In east Mazandaran region, the optimum yield was obtained 71 MT per ha for Thomson navel orange orchard and related norms were N= 2.32, P= 0.17, K= 1.74, Ca= 3.38, Mg= 0.41 percent and for Mn= 40, Zn= 45, Fe= 199, Cu= 14 and B= 80 mg kg-1 dw. data showed that increase of leaf K, P and Mg respectively, resulted in higher yield. High level of Fe in the plant probably resulted in Mn deficiency in the orange Thomson orchards.Keywords: CND, Orchard, Reference Norm, Thamson orange, Valencia orange, yield
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