Determination of alfalfa nutrition requirement in different salinity levels

In this project, alfalfa nutritional requirement was studied in saline soils of Qom province. The experiment was conducted with 3 levels phosphorus (0,100 and 200 kg Triple superphosphate /ha), 3 levels nitrogen (0, 250 and 500 kg Urea/ha splited for per cutting), 2 levels potassium (0 and 100kg Potassium sulfate/ha) and 3 levels salinity in irrigation water (6, 8 and 10 (dS/m)) as 4 factors in randomize complete block design, with 3 replications in 2 years. Results of this study showed that independent effect of nitrogen and phosphorous, resulted in the increase of alfalfa dry matter. with increasing salinity up to level 8 (dS/m), plant need to these fertilizers increased. In the highest salinity level (10 dS/m) a reduction in yield was observed, so that fertilizer application had no significant effect on yield. In none of years, independent effect of potassium on yield was not significant. With increasing salinity levels, concentration of macronutrients including N,P, and K and nitrate alfalfa decreased. Application of nitrogen and potassium fertilizers caused an increase of nitrate (NO-3) concentration in plant.