Physiological effects of salinity on nitrogen fixation in legumes – a review

Among other crop plants legumes are of great significance for agricultural practice since they represent a major source of proteins for human and animal consumption. Through their participation in symbiotic nitrogen fixation in a tight relationship with soil bacteria, atmospheric nitrogen is reduced to ammonium which is a more suitable form of N for utilization of nearly all plant species. Symbiotic nitrogen fixation is a natural means for improving soil fertility advantageous over chemical fertilizing which has lower efficiency and greater economic and ecological costs. High soil salinity seriously decreases crop yield and productivity. In this review, we examine the current knowledge and understanding of the effect of salinity stress on legumes and symbiotic nitrogen fixation and discuss mechanisms and management strategies for improving crop performance. The potential of using legumes as green manure in order to ameliorate plant productivity in saline environments is discussed. Promising technologies for increasing crops nutrient content like the utilization of plant growth-promoting bacteria and the newest research efforts involved in transferring nitrogen-fixing capacity to non-legumes and economically important plant species are outlined.