Activities of rhizosphere microorganisms as affected by application of organic amendments in a calcareous loamy soil. 2. Nitrogen transformations

Abstract

The activities of some nitrogen transforming microorganisms in the rhizosphere of both alfalfa and wheat growing in a calcareous loamy soil of Saudi Arabia as affected by organic amendments have been studied in a greenhouse experiment. The organic amendments were sludge (narrow C/N ratio) and wheat straw (wide C/N ratio), applied at 2% w/w to the soil. Total nitrogen in the rhizosphere and nonrhizosphere soils of alfalfa and wheat significantly increased with application of organic amendments. The increase was especially evident in the rhizosphere region. Ammonium nitrogen values in the soils amended with organic matter were higher in the root regions of both plants than in unamended soil, indicating a high ammonification rate for the former by heterotrophic microorganisms. -from Authors