evaluation of barley–vetch intercrop at different nitrogen rates

to evaluate the yield and quality of barley (hordeum vulgare)–vetch (vicia desycarpa) intercropping, a series of experiments were conducted at the experimental field of the college of agriculture, university of tehran, in karaj (iran) from 2003 to 2005. the ex-periments were arranged in a randomized complete block with a split plot design and four replications. three levels (0, 45 and 90 kg n ha-1) of nitrogen fertilizer and three cropping systems (sole barley, sole vetch and barley-vetch intercropping) were allocated to the main and sub plots, respectively. the barley-vetch intercropping treatment had a replacement arrangement (50: 50) with single alternate rows. land equivalent ratio (ler), was used to compare sole cropping with intercropping systems. results showed the supremacy of intercropping of barley and vetch over single crops. generally, increas-ing nitrogen fertilizer caused a decreasing trend in the biological efficiency of intercrop-ping. the highest ler for grain was obtained in control (n fertilizer free) plots (ler= 1.145). nitrogen fertilizer increased the forage yield, grain yield, crude protein content, and crude protein yield of barley and vetch in sole and intercrops. nitrogen application increased water use efficiency. in this study, barley was the dominant crop. the inter-cropping vetch and barley had the highest productivity and crude protein yield.