The Role of Organic Matter, Especially Manure, in the Nutrition of Rice

Abstract

1. Rice plants grown in sand or solution culture were found to respond to the addition of manure with marked increases in growth. This effect of manure could not be duplicated by variations of the composition of the major or minor elements of the nutrient solution within wide limits. A systematic investigation of the nature of the effect of manure and other kinds of organic matter on the growth of rice was therefore undertaken. 2. The findings of earlier investigators that rice seedlings utilize ammonium rather than nitrate as a source of nitrogen were confirmed. In addition, it was found that ammonium nitrogen is toxic to the rice seedling at relatively low concentrations. 3. Manure and other kinds of nitrogenous organic matter are able to serve as sources of nitrogen for cultures of rice seedlings. The nitrogen of protein, peptone, and various amino acids is shown to be available to rice seedlings. These compounds are probably decomposed by micro-organisms before their nitrogen is utilized by the plant, since under aseptic conditions the nitrogen of protein does not appear to be utilized by rice. 4. The influence of manure on the growth of rice under the present experimental conditions is shown to be quantitatively attributable to the organic nitrogen content of the manure. The nitrogen of organic matter appears to serve as a supplement to the relatively low concentrations of free ammonium salts which are tolerated by the plant. 5. No evidence was found to suggest the presence in manure of a specific organic substance important in plant growth.