Nitrogen Transformations in the Soil

Abstract

IN his presidential address to the National Academy of Sciences, India, on January 15, Prof. N. R. Dhar gave a very comprehensive account of his work on nitrogen transformations in the soil, various aspects of which have recently been described in NATURE (137, 462, 629, 1000; 138, 648, 1060; 1936). Further evidence was provided of increases both in soil nitrogen content and in crop yield following the application of molasses, and striking results were reported in the reclamation of alkali land by molasses on the practical scale. Other carbohydrate-rich materials, and the sodium salts of fatty acids, were also shown to promote nitrogen fixation. Cow dung had a double action, not only supplying extra nitrogen but also leading to nitrogen fixation as well. With more highly nitrogenous materials, however, such as oil cake or sulphate of ammonia, a loss of nitrogen from the soil took place, especially if it was exposed to sunlight. This loss was reduced when leaves or cow-dung were also added’, while molasses converted the loss into a gain, nitrogen fixation occurring in spite of the presence of much available nitrogen.