Deficit Irrigation and Split N Fertilization on Wheat and Barley Yields in a Semi-Arid Mediterranean Area

This study investigated the interactive effects of different rates of deficit irrigation and timings of N application on wheat and barley yields since there was no report on this important subject. Field experiments in strip-plot designs using sprinkler line sources were conducted for two years at a semi-arid Mediterranean site. The experiments consisted of 4 and 7 irrigation levels with 3 and 6 N treatments in 4 replicates in 2002-03 and 2003-04, respectively. In both years, there was a significant irrigation-by-N interaction on wheat grain yield but not on barley. In 2003-04, N application at stem elongation and heading produced the highest wheat grain yield at the four higher irrigation levels, but highest yield was obtained when N was applied at sowing and tillering at the two lowest irrigation levels. Nitrogen application at stem elongation and heading also gave the highest grain N content. The existence of interaction due to irrigation-by-timing of N application in wheat but not in barley could be because wheat has a higher N uptake after anthesis but lower nitrogen remobilization efficiency than barley. Results suggested that wheat farmers better apply N at stem elongation and heading for a higher yield and grain N content unless they are not irrigating or irrigate with minimum amount of water.