THE COMPOSITION OF NATURAL ORGANIC MATERIALS AND THEIR DECOMPOSITION IN THE SOIL

Publisher Website
Google Scholar
Abstract
A plant contains the largest amount of N and ash and the lowest amount of lignin at an early stage of growth. With advancing age there is a gradual decrease of the N ash, fat content and especially of the water soluble portion, and a gradual increase of the lignin, pentosan and cellulose content. Young rye plants contained 2 1/2% N, while at maturity the N content of the stems and leaves was only 0.24 %. The cellulose content increased from 18 to 36% and the lignin from 9.9 to 19.8%. The more mature plants decompose much more slowly than younger plants. The rapidity of decomposition is directly related to the amount of water soluble constituents and the N content, and is inversely related to the lignin content. When the N content of the plant is about 1.7%, it is just sufficient to cover the requirements of the microorganisms which are active in the decomposition of the material within a period of 4 weeks. If the N content of the plant is less than 1.7%, N starvation will take place during the earlier stages of decomposition and additional available N will be required. If the N content of the plant is above 1.7%, the excess of N will be readily liberated in an available form within even the first 4 weeks of decomposition. The water soluble substances of the plant are the first to be decomposed, followed by the decomposition of "the pentosans and celluloses. The lignins decompose less rapidly even under aerobic conditions than any of the other major plant constituents and tend to accumulate in the soil. The accumulation of the lignins and the synthesis of microbial nitrogenous complexes account for the increase in the soil "humus" as a result of the decomposition of organic materials.

This publication has 1 reference indexed in Scilit: