To study the effect of salinity of irrigation water on biological nitrogen transformation. Lab experiments were conducted at ascientific unit research in college of agriculture university of Baghdad. soil samples were collected at depth 0-30cm from college field treated with mixture of following salts KCl ,MgCl2 , NaCl, CaCl2 to give four levels of salanity : 0.3 ,2.5 , 4.8 , 7.2 ds m-1, the treated soil samples were put in plastic cans(200gm),nitrogen fertilizer with two levels were added (as urea)(100kg N ha-1)(200N kg ha-1).The samples were incubated four weeks at 30*c. Soil samples were taken to determine NH4+ , NO3– , SAR and the number of nitrobacter and nitrosomanas bacteria .The results of the experiments showed asignificant increase in the amount of NH4+ in both treatment of tap water , the first level of nitrogen fertilizer after two weeks of incubation was 305.5 mg N kg-1 . while the amount of NH4+ decreased to 291.8 mg N kg-1 when the consentration of salinity in creased . Also there was adecline in the amount of NH4+ when the value of SAR increased and gave 281.5 mg N kg-1 soil , the elevation of salinity of the water caused reduction in the oxidation of NH4+ to NO3– which give 94.7mg N. the high salinity of water played an important role in SAR value which increased from 18 to 33.5 at 7.2 ds.m-1 , the results showed also was a clear decline in the the sailinty of water increased after four weeks of incubation number of nitrosomonas from 0.401 x 106cfu to 0.014×104 cfu . gm-1 when. we can canclude that nitrobacter bacteria more sensitive to salinity than the nitrosomonas.
Abdul Hameed, B. A., Agric College, Baghdad Univ.
Nada hamaid majaid, Agric College, Baghdad Univ.
Farage H. A., Agric College, Baghdad Univ.