Improving N management would eventually depend on the accuracy with which the N status of plant can be assessed. the usefulness of SPAD chlorophyll meter readings for plant N assessment is based on the direct proportionality between leaf chlorophyll and leaf N concentration. Field experiments were conducted during 2005 and 2006 to determine the response of grain yield, leaf and grain nitrogen concentration and chlorophyll content of leaf to nitrogen fertilizer application rate. Dynamics of chlorophyll was measured by using a SPAD chlorophyll meter on the youngest fully developed leaves of a full season hybrid of maize. the average of SPAD values were increased with the increasing of fertilizer application, irrespective of the growth stage. SPAD readings at R1 growth stage accurately predicted yield and nitrogen concentration in leaf. Incraesing nitrogen fertilizer up to 400 kg.ha-1 significantly increased maize biological yield and SPAD readings, but higher N application did not significantly increase these parameters further. In general results showed that using SPAD meter is not a good technique for early prediction of N status in corn. Based on our results photosynthesis maturity is the best time for predicy\tion of N status in corn, because as this time leaf chlorophyll reaches to its maximum.

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