This investigation was carried out in the experimental orchard, Faculty of Agriculture, Assiut University, Egypt, to study the influence of slow release N, organic and bio-form fertilizers on growth vigour and fruiting of Balady mandarin trees during 2006, 2007 and 2008 seasons.
The experiment was arranged in a randomized complete block design with three replications, using a tree as an experimental unit and it consisted of 7 treatments.  Fast release nitrogen fertilize was added at three equal doses in March, May and August, while the slow-release N, and bio-fertilizers were applied once at the start of spring growth.
The obtained results could be summarized as follow:
-    The application of slow release N and other three fertilizers once a year surpassed the application of fast release (mineral) N in improving shoot and leaf traits.
-    The slow release-N fertilizer and organic, bio and inorganic forms (three forms) significantly increased N, P and K contents of leaves as well as the total carbohydrates and C/N ratio of shoots compared to using the fast release-N fertilizer.
-    The fertilization using either 80% of the recommended N dose as slow release-N or other three forms would achieve a beneficial improvement to vigour and nutrient status of the trees.
-    The use of slow release-N fertilizer and either bio-fertilization or organic and bio-forms plus mineral-N form increased the yield and improved the fruit quality of Balady mandarin trees.
-    No significant influence was detected on such traits due to rising the slow release-N from 80 to 100% of the recommended N dose (RND).
It is evident from the foregoing results that using either 80% of the RND as a slow release-N fertilizer or other three fertilization forms improved the

tree nutrient status, yield and fruit quality. In addition, it minimized the production costs and environmental pollution which could be occurred by excess of chemical fertilizers