Irrigation water salinity affect dynamics of organic carbon and nitrogen derived from Alfalfa and Barley residues

Incorporation of plant residues in soils of arid and semiarid regions is a major principle for sustainable agriculture. This experiment was performed to evaluate the effects of saline of irrigation water on organic carbon and nitrogen dynamics. For this purpose, a pot experiment with split – split plot arrangement with three replications was conducted in University of Zanjan using litter bag method. The Examined factors were two types of plant residues (barley and alfalfa residues), three salinity levels of irrigation water (0.3, 4 and 8 dSm-1) and four incubation time intervals (1, 2, 3 and 4 months). The results showed that the amounts of organic carbon and nitrogen lost decreased by increasing the salinity level of irrigation water. The amounts of organic carbon lost after 4 months were respectively 65.52, 61.71 and 58.89% for alfalfa residue and 60.95, 51.95and48.33% for barley residue when salinity levels of irrigation water adjusted at 0.3, 4 and 8 dSm-1correspondingly. The corresponding amounts of organic nitrogen lost were 65.99, 54.02 and 48.09% for alfalfa residues and 61.04, 52.31 and 44.13% for barley residues respectively. The results showed that by increasing the salinity level of irrigation water from 0.3 to 4 and 8 dSm-1, the amounts of organic carbon lost from alfalfa and barley residues decreased by 5.82 and 10.12% and 14.77 and 20.71% respectively. The decrease in the amounts of organic nitrogen lost with increasing the salinity levels of irrigation water were 18.13 and 27.12% for alfalfa residues and 14.30 and 27.70% for barley residues respectively.