Abstract. Environmental conditions such as soil salinity, high temperature, and soil toxicity of heavy metals have harmful effects on plant s growth and nitrogen uptake by root and its metabolism. Changing in osmotic pressure usually relates to varying Cl concentration and excessive sulphate concentration also leads to plant toxicity more than Cl- .Increasing in N concentration in saline soil solution has a positive effect on the other nutrient uptake. Many of experts believe that the important progress in cereals production in recent half century has been obtained by harvest index (HI) increasing not necessarily from total biomass growing. A green house experiment was carried out in Ferdowsi University of Mashhad. This experiment was included six Cl-/SO4= ratios consist of (C0S0, C1S1, C1S2, C1S3, C2S1 and C3S1) as main treatments and two nitrogen fertilizers (N1=75 Kg/ha and N2= 150 Kg/ha) as sub treatments by using complete randomize design (factorial) with three replications to study Cl- and SO4= salinity and nitrogen on amount, uptake and nutrient interaction in barley, grain harvest index, N,P,K,Cl,SO4 harvest indices determining, N agronomic efficiency (PFNUE) , N recovery efficiency (PFNRE) and finally N physiological efficiency (PFNUTE) measuring under the predominant of Cl- & SO4= condition. The results showed that maximum grain and straw yield existed in C1S3 and C1S2 ratios and also maximum N, P and K concentration presented in straw and grain in C1S2, C1S3 and C1S1 ratios. The maximum of N, P and K concentrations under the effects of Cl-/SO4= ratios and nitrogen condition showed in low Cl- concentration and high concentration of SO4= too. Maximum of grain and N harvest index showed in C1S3 treatment, but C1S1 treatment for P. Maximum of grain and N harvest index under the effects of anion ratios and nitrogen showed in C1S3N2 and C1S3N1 treatments, whereas C1S1N2 and C1S1N1 treatment for P harvest index. The results also indicated that S harvest index was higher in high Cl- ratios (C2S1 & C3S1) because of high sulphate concentration in biomass rather than it in grain in sulphate salinity. The results of experiment also showed that PFNUE & PFNRE were maximum in high SO4= and low Cl- concentration (C1S3 and C1S2) treatments, however, PFNUTE process was opposed to PFNUE & PFNRE. So that, maximum of PFNUTE showed in high Cl- and low SO4= concentrations (C3S1 and C2S1) that it was the reason of antagonistic effect between SO4= and NO3- . Observed process in PFNUTE, PFNUE & PFNRE was similar in two levels (75 and 150 Kg/ha) of N and it was double for 75 Kg N /ha rather than 150 Kg N/ha. The use of N fertilizer in saline soils may prevent the stresses of salinity particularly Cl- toxicity through the improvement in growth and yield of barley when SO4= is a dominant anion.

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