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Effects of different levels of nitrogen and phosphorous fertilizers and irrigation intervals on some agronomic traits of Speedfeed, a forage sorghum
variety, were studied in a split plot design for two years in two locations-Karaj and Khossrovshahr. Combined analysis of data showed that differences between years and location were significant for all traits studied, but yearlocation interactons for the traits were non-significant. Different levels of
phosphorous did not affect fresh-feed, dry-feed yield, plant height and tiller number significantly, while phosphorous year interaction in relation to tiller
number was significant. Significant differences between nitrogen levels as well as between irrigation intervals for fresh-feed yield and dry-feed yield were obtained. Highest fresh and dry-feed yield, as well as plant height were obtained when 8 day irrigation intervals were applied. Diffierence between this interval with other irrigation intervals was significant for these traits. Applying 200 Kg N/ha produced highest dry and fresh-feed yield, but it was not significantly different fll)m 150 Kg N/ha treatment.