Abstract
In order to evaluate the effect of different nitrogen application methods on wheat canopy, leaf chlorophyll, and yield, a field experiment with a split plot arrangement in complete randomized block design with four replicates was conducted in 2006. Basal dressing in three levels (with no basal dressing, strip and distributing nitrogen fertilizer) as main plot and top dressing in six levels (distributing on tillering, two distributing on tillering and before spike appearance, water soluble fertilizing with herbicide application before spike appearance, two water soluble fertilizing on tillering and before spike appearance, two application: one distributing on tillering and one water soluble fertilizing before spike appearance and finally, three water soluble fertilizing on tillering, before spike appearance and milking period) as subplot were applied. The amount of fertilizer in strip application was 2/3 of distributing method. In the compartmented application, the amount of applied fertilizer was two third of distributing fertilizer method. Leaf area index for no basal nitrogen fertilizer application treatment was 21% lower than the mean of LAI for band and broadcasting application treatments. Band and broadcasting application of basal nitrogen fertilizer caused 454 and 61.6% increase in leaf area per plant in comparison with no basal nitrogen treatment respectively. Light transition from canopy for no basal nitrogen fertilizer treatment was 81.1% higher than the mean of light transition for band and broadcasting nitrogen application treatment. Although there was not significant differences between band and broadcasting application method, the lowest and the highest leaf chlorophyll was belong to no basal nitrogen and broadcasting treatment respectively. Based on leaf chlorophyll, split or integrated treatments of top dressing application of nitrogen fertilizer in spite of reducation of nitrogen application, because of optimization, did not have significant difference with conventional treatment (wholly distributing of top dressing nitrogen fertilizer on tillering).

Keywords: Wheat, Nitrogen fertilizer, Basal dressing, Top dressing, Leaf chlorophyll