Effects of salinity and N nutrition on prussic acid (HCN) concentration of forage sorghum (Var.Speedfeed)

The effects of salinity and nitrogen nutrition on growth , protein content and prussic acid concentration of forage sorghum Var. Speedfeed was determined in sand and hydroponics culture in greenhouse and growth chamber. The treatments were included two salinity levels (0,100 mM NaCl) and three nitrogen source (nitrate, ammonium and ammonium plus nitrate ). The dry weight of roots, shoots and leaves, length of shoot, concentration of Na+, K+, protein and prussic acid in plants were determined after harvesting . The results indicated that salinity effect on all parameters was significant, whereas effects of N nutrition and N+ salinity was significant only on roots, shoots and leaves dry weight and shoot length. Salinity induced significant reduction in plant growth protein and K+ concentration in shoots and roots. Salinity also resulted in increase of Na+ and prussic acid concentration of shoots. The prussic acid concentration was significantly lower in ammonium treatment without salinity than nitrate and ammonium plus nitrate treatments. Salinity induced significant increase in prussic acid concentration in ammonium feed plants compared with other N nutritions. The highest K+ concentration and the lowest Na+ concentration were observed in nitrate and ammonium plus nitrate treatments under salinity. consequently lead to the lower toxicity. On the contrary, ammonium nutrition resulted in the higher accumulation of Na+ and consequently the higher toxicity that lead to protein reduction, prussic acid accumulation and ammonium toxicity. Without salinity, ammonium is the best N from nutrition. However, under salinity, nitrate and ammonium plus nitrate are recommended due to the higher protein and K+ concentration and the lower prussic acid Further experiments are recommended to confirm these results.