This book deals with biotic and abiotic factors of the environment and focuses  an emerging branch of science which deals with the input of secondary metabolites of one plant, release from any part of plants either by means of leaching by rainwater, dew, fog or volatilization of volatile compounds or root exudates into the environment, on other plants. This study adopted Many crop plants thrive well in the water logging conditions where other aquatic weeds also grow. This book also highlights on allelopathic effect of water hyacinth (E. crassipes) on seed germination and seedling growth only on limited crop plants.