Foliar nutrition diagnose of red Fuji apple during different periodsin the Weibei Dry Highland of Shaanxi Province

Shaanxi Province is the largest apple production region in China. Realizing high-yield and high-quality of apple production plays an important role in ensuring the farmers income. However, there exist some problems in apple production such as excessive application of nitrogen fertilizer and unreasonable use of microelements fertilizer. In order to promote rational fertilization of apple production in Weibei Dry Highland, the mineral nutrient content in red Fuji apple leaves during different growth stages were determined. Apple tree leaves were sampled at June, July and August respectively in Heyang County, Shaanxi Province, and contents of mineral nutrients were analyzed. Then DRISes proposed by Beaufils, Jones and Elwali & Gascho was used to diagnose nutrient status and requirements of red Fuji apple tree. Results showed that nutrients contents in apple leaves varied from June to August. During this period, high yield trees (yield > 25 kg per tree), N content decreased in July and then increased slightly in August, while P content decreased all the time. For low yield trees (yield ≤ 25 kg per tree), N content decreased all the time, the change of P just followed the tendency of N in high yield trees. Other nutrients showed the same trend in both kinds of trees: K and Zn decreased; Ca and Mg increased; Cu, Fe and Mn increased in July and then decreased in August. The diagnosis parameters determined by DRIS standard program were different during different periods. Compared with the diagnosis indices calculated with method of Elwali & Gascho, those with methods of Beaufils and Jones were significantly correlated with nutrient content, and the corresponding order of nutrient requirement was similar. From June to August, the elements needed mostly were K, Fe, Ca+Mg by Beaufils and K, Ca, Ca+Mg by Jones for high yield trees, and K, Fe, N for low yield trees. The results suggested that leaf nutrient diagnose should be conducted during different growth periods of red Fuji apple.