THE STUDIES TO CALIBRATE the rapid tissue test with the nitrogen nutritional status of sorghum were conducted in a nitrogen deficient field on the Rosolia Ranch near Orland. In 1970, initial soil samples were taken and plots laid out in a randomized complete block design with six treatments and three replications. The plots were 15 ft wide and 50 ft long. The treatments consisted of 0, 50, 100, 150, 200, and 250 lbs of nitrogen applied per acre. The nitrogen (as ammonium sulfate) was applied pre-plant and disked into the soil. Sorghum, variety NK 222, was planted on July 4, 1970 by drilling on 12-inch row spacing.