Management of soil nitrogen supplies for high yields and quality is one of the major problems fac ing the sugarbeet industry at the present time. If soil testing procedures can be success­ fully used to predict nitrogen fertilizer requirements, the poten­ tial benefits to the industry are substantial. Until recentl y, the concept that soil mineral nitrogen was not a good index of nitrogen avai lable for crop production was widely accepted. Scarsbrook (6) states, "Although nearly all available nitrogen is in the NI-I.1+ or N03' form , the amount in the soil at a givell time is a poor indicator of the nitrogen avail­ ability to crops during th e gTowing season". During the past few years this concept has been chall enged by a number of in­ vestigators, particul arly in the wes tern USA and Canada. Soper and Huang (7) in Manitoba found that percent of maxi­ mum barley yields were highly correlated with log of N03 ' ni­ trogen to a depth of 4 ft. H erron et al . (3) fou nd in Nebraska that yield of corn on unfertilized plOlS w'as highly correlated with residual NO g ' in the soil profile. James et al. (4) have shown that nitrogen uptake and sugar percentag(, of sugarbeets in cen­ tral 'Washington are highly correlated with total soil NO g' to a depth of ::; ft. Geist et al. (2) found that yield and quality of malting barley in Colorado was closely related to the sum of the fer tilizer nitrogen plus the soil mineral nitrogen found in the top foot of soil at planting time. T hey also sho'wed that this r elation could be improved by including an index of es timated nitrogen mineralized from the organic forms as detennined by a m odel proposed by Reuss and Geist (5). The success of these inves tigators in relating yield and ni­ trogen uptake to N O g ' or N 0 3plus NH,+ nitrogen , in spite of the previously widely accepted con cept that these parameters are poor indicators of nitrogen availability to crops, is undou bt­ edly r ela ted to modern fertilizer practices that often su pply ni­