Y. Emam - Department of Agronomy, College of Agriculture, Shiraz University, Islamic Republic of Iran.
A. R. Borjian - Agricultural Research Center, Khanssar, Islamic Republic of Iran.

Foliar urea application is one of the nitrogen (N) application methods in cereal grain crops. Yield and yield components may be affected by foliar urea application. To investigate the effect of rate and time of such treatment on yield and yield components of two winter wheat cultivars, a field experiment was conducted at Badjgah, Agricultural Research Farm (۲۹° ۳۶ N, ۵۲° ۳۲ E) of Shiraz University, Shiraz, Iran during ۱۹۹۸-۹۹ growing season. The experimental treatments were two winter wheat cultivars (‘Phalat’ and ‘Marvdasht’), five levels of foliar urea application (۰, ۸, ۱۶, ۲۴ and ۳۲ kg N ha-۱) at three times of application (pre-anthesis, anthesis and post-anthesis). The experimental design was a randomized complete block one with treatments arranged as split-plot factorial with three replicates. The results showed that cultivars responded differently to the rate of foliar N feeding so that, over the growth stages, Marvdasht cultivar produced significantly greater grain yield (+۱۹%) by application of ۸ kg N ha-۱, whereas, the Phalat cultivar had greater grain yield (+۲۷%) when it was supplied by ۱۶ kg N ha-۱. Increase in grain yield was mainly due to an increase in number of grains ear-۱. The fertile ears m-۲ and mean grain weight were not significantly affected by foliar urea feeding, however, the harvest index and biological yield were increased. The pre-anthesis foliar feeding with urea resulted in higher yields as compared with later applications. Also the early foliar urea feeding increased the harvest index from ۴۲.۴% to ۴۶.۹% at ۳۲ kg N ha-۱ in Marvdasht cultivar. The results of the present investigation also suggest that late foliar application could decrease nitrogen use efficiency.

Grain yield, Foliar N application, Winter wheat