A four year trial was conducted during 2006-2009 seasons in Balady mandarin orchard .Two N fertilizer
forms: a. traditional N fertilizers i.e. ammonium sulfate and ammonium nitrate and b. controlled release N
fertilizers namely urea formaldehyde and phosphorus coated urea .Two N fertilizer rates 200 & 300g N/tree and
400 & 600g N/tree were tested for conventional N fertilizers in an expected "Off" and "On" years, respectively.
Moreover, 100 & 150g N/tree and 200 & 300g N/tree were tested for controlled release N fertilizers in an
expected "Off" and "On" years, respectively. Application frequency of traditional N fertilizers was tested under
four application systems, whereas, controlled release N fertilizers were applied once a year. Briefly, the two
tested controlled release N fertilizers at the two rates reduced N application rate and enhanced the studied tree
productivity parameters without adverse effect on fruit quality.