The culture of citrus in Florida is frequently associated with sandy soils which allow rapid leaching and lead to nitrogen deficiency symptoms in the trees. The application of commercial forms of nitrogen to such soils leads to the question of the efficiency with which citrus trees utilize this nitrogen. The present article deals with certain observations made on the absorptiojn of nitrate, ammonium, and urea nitrogen by year-old budded citrus trees. Methods Twelve trees of Valencia orange budded on rough lemon root stock were set in coarse (I to 1 inch) silica gravel. The containers were concrete conduit tile measuring one foot inside diameter and five feet tall, and were supported by concrete blocks to a height one foot above the ground. The lower end of each container was plugged with concrete at an angle, with an orifice at the lower edge to allow for complete drainage. The interior of each container was painted with an inert emulsifiable asphalt compound. In front of each container was a 5-gallon glass carboy for the appropriate nutrient solution, which was delivered to the container through the orifice by compressed air and returned to the carboy by grav- ity (6).The methods employed to analyze the amounts of the different forms of nitrogen were all colorimetric, using a Fisher Electrophotometer, and employing standard colorimetric procedures slightly 'adapted to the requirements of the solutions themselves. Urea nitrogen was determined by means of Xanthydrol reagent (4, 5). Ammonium nitrogen was determined with Nessler's reagent (5, 9). Nitrite nitrogen was determined with dimethylaniline reagent (12). Nitrate nitrogen was determined by means of brucine reagent (5,8,9,11). Results The trees, after being severely pruned of roots and shoots, were set in place May 7, 1948. Nutrient solutions were supplied starting May 10. The first leafy sprouts appeared after one week. The nutrient solutions were renewed at varying periods, depending on the amounts of the original forms of nitrogen changing to other forms of nitrogen, or the amounts

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