Early Sowing and Irrigation - Differential Response of Barley and Oat.

In cool Mediterranean areas, ensuring early emergence of barley and wheat by early sowing and early irrigation gives significant higher seed and straw yields. This study investigated if oat yields would benefit from early sowing and early irrigation similar to barley. The two-year experiment was conducted on stony fields with shallow soils at the Agricultural Research and Educational Centre of the American University of Beirut in central Bekaa Valley, Lebanon. The long-term annual precipitation of the site is 513 mm, 58% of which falls in December-February. There were 3 irrigation treatments - no (control), early (EI), and late (LI) irrigation, with 4 replicates. Seeds were sown in late October instead of the usual mid-November. After sowing, EI received 30 mm irrigation immediately. The LI treatment received irrigation (100 mm in 2008; 60 mm in 2009) when barley was heading. Seedling emergence was 20 days earlier under EI in 2007-08, which had 367 mm precipitation. In 2008-09, which received 594 mm precipitation, rain came 4 days before the scheduled sowing and early irrigation. There was significant irrigation x crop x year interaction for grain and shoot dry-matter yields. Barley yields under EI were higher (110% in seed; 54% in straw) than the control in both years, and were higher (42% in seed; 40% in straw) than LI in 2007-08. In contrast, there were no significant differences in oat yields under the three irrigation treatments in both years. Similarly, EI led to higher harvest index and taller plants in barley but not in oat. Heading and maturity were 15 days and 5 days earlier under EI than the control in barley, but only 4 and 2 days in oat, respectively. In conclusion, unlike barley, early sowing and early irrigation did not increase grain and straw yields for the later maturing oat.