Study on optimal nutrient level and the effects of fertilizers in improving the nutritional status of the (Acer negundo) for urban greening

To improve the nutritional status of Acer negundo trees, a three- year experiment was conducted in the National Botanical Garden of Iran which is currently suffering under low soil nutrient availability and occasional symptoms of yellow leaves. Firstly, samples were taken from both weak and vigorous trees in different stands located inside and outside the project site. Next, a factorial experiment based on a randomized complete block design with four replications was conducted, in which the factor A included the application of organic, inorganic and mixed fertilizers. The factor B included two levels of applying fertilizer via 1) solution in the irrigation water and 2) deep placement. The leaf samples were analyzed at growing season for NPK. Statistical comparison of means based Duncan's test showed an increment of N and K elements in leaves compared to control samples following two-year fertilization. Furthermore, an analysis tree vitality based on leaf chlorophyll availability and leaf nutritional status showed no differences in leaf P concentration between fertilizer treatments as a function of fertilizing method. As a conclusion, optimum levels of N and K content in A. negundo leaves are 1.90 % and 1.20 %, respectively.