Impact of Different Nitrogen forms on Soil Fertility and Cowpea Productivity under Conditions Saline Soil

The field experiment was carried out at the south-west portion of Shall El-Tina region, north Siena Governorate Egypt. The study investigated evaluations of different nitrogen fertilizers sources (ammonium nitrate, ammonium sulphate and urea fertilizers) and rates (100%, 75% and 50% recommended dose of all different nitrogen forms) alone or combined with bio-fertilizer (Rhizobium radiobacter sp.) strain on improve nutrients available and contents in cowpea productivity in newly reclaimed saline soil conditions during two summer seasons 2019 and 2020. The studies treatments were disturbed among the experimental plots in split design. The obtained results showed that using ammonium sulphate fertilizer was more effect on EC, pH, and available N, P, K, Fe, Mn and Zn values by increasing application rates compared with other treatments. Moreover, data recorded the applied ammonium sulphate75% with bio-fertilizer was increase of plant height, weight of 100 seeds, weight of pods (g plant-1), seeds yield (ton fed-1) have been affected by inoculation with bio-fertilizer combined with different nitrogen forms and different application rates than other treatments. The highest values of N, P, K, Fe, Mn and Zn concentrations and uptake in seeds were obtained with ammonium sulphate application combined with bio-fertilizer compared with other treatments. The increase of chlorophyll, protein contents in cowpea plants with decreasing soil salinity, while the increase of proline content was increasing soil salinity. The application of ammonium sulphate at application rate 75% N combined with bio-fertilizer improves soil properties and cowpea productivity under saline soil conditions.