Maintaining soil fertility and the use of plant nutrients in sufficient and balanced amounts is one of the key factors for increasing crop yield and decreasing adverse environmental effects and pollutions arising from nonpoint fertilizer usage. Two field experiments were conducted during the summer and winter seasons at experiment at station of EL-Nubaria area El-Behira Governorate, Egypt. The aim of this study was to compare the effect of different rates and forms of nitrogen fertilizer, i.e., ammonium sulphate (20.6% N), ammonium nitrate (33.5% N), and Enciabien, 40% N (slow-release) with or without inoculation by (plant growth promoting rhizobactteria) (PGPR) on yield and nutrients concentrations of maize and wheat plants as well as soil fertility of calcareous soil and enzyme activity. Three sources of nitrogen fertilizer were applied as hand broadcast on the soil surface at three rates (50, 75 and 100 %) from recommended doses of minerals nitrogen (60, 90 and 120) and (40, 60 and 80) Kg N for maize and wheat plants. The obtained results showed that there were significant effects on grain and straw yields, as well as nutrients concentrations of both maize and wheat plants due to N sources and rates. In general, Enciabien gave higher grain and straw yields in both maize and wheat crops than ammonium sulfate and ammonium nitrate. Data indicated that rate (100%) from recommended doses increased significantly yield and nutrients concentrations than other N doses. The present results focused highlight on the practical importance of adequate N fertilization and different rates of N source on (grain and stover) yields and (grain and straw) yields in maize and wheat crops and suggest that Enciabien application at (100%) N from recommended doses will be about adequate to meet crop N requirements. The obtained results indicated that the concentration of N, P and K in (grain and stover); (grain and straw) of maize and wheat plants were clearly significantly higher under the application of Enciabien fertilizer followed by ammonium sulphate and lately ammonium nitrate. On the other hand, plants received Enciabein at rate of (100%) N from recommended doses showed significantly effect on Fe, Mn, Zn and Cu concentration than those received ammonium sulphate or ammonium nitrate fertilizer at the same rate. The residual nitrogen in the soil was significantly increased with application of nitrogen fertilizer. It was noted that plots that received (100%) N from recommended doses significantly retained more nitrogen and was higher by 12.3 and 5.9%, respectively than application rates of (50% and 75%) N from recommended doses. It is worthy to notice that ammonium sulphate yielded the highest values of soil available nitrogen than ammonium nitrate and Enciabein. But, the residual phosphorus and potassium in the soil were significantly decreased with increased application rate of nitrogen fertilizer. The results indicated that the use of ammonium sulphate surpassed the ammonium nitrate and Enciabein in increasing soil available phos...
