ABSTRACT
Zag-1 phage was isolated from the rhizosphere of cowpea plants grown in fields in Sharqia, Egypt. The existence and propagation of cowpea Rhizobium and its Zag-1 phage were studied in clay and sandy soils. The maximum bacterial counts were recorded in clay soil after seven weeks of incubation compared with eight weeks for sandy soil. The infectivity of Zag-1 phage persisted for five and ten weeks in clay and sandy soils, respectively. Testing the roles of Zag-1 phage on nodulation and growth of cowpea showed significant alterations. Zag-1 phage inhibited nodule formation in plants grown in sterile potted clay soils but with only a reduction for those grown in sandy soil. Appreciable reduction was obtained for the growth and total nitrogen content of plants grown in both soils