The use of soil amendments has been proposed as a means for improving soil quality, crop growth and limiting the severity of soil- borne plant diseases. Several by-products generated from processed agricultural crops which are generally regarded as wastes may be recycled in crop production systems.This monograph presents an assessment of four agricultural wastes ?maize husk, locust beans chaff, rice husk and soya beans chaff as organic amendment for soil. The changes in soil properties; the response of soil borne pathogenic microflora to the soil amendments; the effects of these amendments on the growth and yield of Cowpea (Vigna unguiculata L. Walp.) are presented. This crop is the most economically significant African traditional legume crop, which is important for poor people in less developed countries (Valenzuela and Smith, 2002). Poor farmers in developing countries who have difficulty in controlling crop diseases and maintaining soil fertility due to financial constraint will find the information herein valuable. Additional information on improvement of soil properties by recycling of agricultural by-products is provided for all students of Agriculture.