Section II Essential Elements––Macronutrients 2 Nitrogen Discovery of the essentiality of nitrogen is often credited to de Saussure (1–3), who in 1804 recognized that nitrogen was a vital constituent of plants, and that nitrogen was obtained mainly from the soil. | 7 5 2006 8 53 AM Page 19 Section II Essential Elements Macronutrients 7 5 2006 8 53 AM Page 20 7 5 2006 8 53 AM Page 21 2 Nitrogen Allen V. Barker University of Massachusetts Amherst Massachusetts Gretchen M. Bryson University of Massachusetts Amherst Massachusetts CONTENTS Determination of Nitrogen Metabolism and Nitrogenous Constituents in Nitrate Assimilation .23 Nitrate Nitrite Ammonium Assimilation .23 Glutamine Glutamate Glutamic Acid Dehydrogenase .24 Proteins and Other Nitrogenous Diagnosis of Nitrogen Status in Symptoms of Deficiency and Concentrations of Nitrogen in Concentrations of Nitrogen in Plant Ratios of Concentrations of Nitrogen to Other Nutrients in Nitrogen in Soils .32 Forms of Nitrogen in Organic Nitrogen in Soil .33 Inorganic Nitrogen in Soil Testing for Determinations of Total Biological Determinations of Availability Determination of Inorganic Amino Sugars .38 Nitrogen Properties and Use of Nitrogen Anhydrous Ammonia 82 N .40 Aqua Ammonia 21 N .40 Urea 46 N .40 .
