BIOMASS PRODUCTION AND WATER-USE EFFICIENCY OF BARLEY AND WHEAT PLANTS WITH DIFFERENT IRRIGATION INTERVALS AT VARIOUS WATER LEVELS

Biomass production in terms of dry-matter yield of both straw and grai ns of barley (Hordeum vulgare L., cv. 'Walfajr') and wheat (Triticum a estivum L., cv. 'Karaj I') plants subjected to water stress were studi ed at the College of Agriculture, University of Tehran Experimental fa rm located in the city of Karaj, Iran. The treatments consisted of two irrigation intervals, 7 and 14 days. Six water levels, 100, 80, 60, 4 0, 20, and 0% of the crops' total water requirements were used at each irrigation interval. The experimental units consisted of 2.5m x 2.5m plots replicated three times for each treatment. A 1m x 1m sub-plot at the center of each 2.5m x 2.5m plot was selected and the plants were harvested to prevent border effects. After each harvest, the straw and the grains were separated and weighed. Total dry-matter yield of stra w and grains significantly decreased by decreasing applied water level s (especially, at the lower water levels, 40, 20, and 0%) and increasi ng irrigation intervals for both plants. Water use efficiency (WUE) wa s higher at the higher applied water levels for the straw than for the grains for barley, however, the trend was reverse for wheat plants. T he WUE decreased for straw by deceasing applied water in both barley a nd wheat plants.