Effect of saline irrigation on the biomass yield, and the protein, nitrogen, phosphorus, and potassium composition of alfalfa in a pot experiment

Effect of saline irrigation was studied on the germination, biomass yield, protein content, and nitrogen (N), phosphorus (P), potassium (K) composition of three alfalfa (Medicago saliva) cultivars in a pot experiment. The percent germination of alfalfa cultivars decreased to 15% (Hassawi), 13% (Supreme), and 30% (CUF-101) receiving irrigation water having total salinity of 12.3 dS/m; and up to 30% (Hassawi), 22% (Supreme), and 64% (CUF-101) with irrigation water salinity of 16.5 dS/m. The mortality of young alfalfa seedlings was 100% after two weeks of germination with irrigation water salinity of 12 dS/m and above. The mean green-matter yield was 56.72 g (Hassawi), 54.29 g (Supreme), and 59.91 g (CUF-101) per pot irrigated with water having total salinity of 7.8 dS/m. The difference in yield was not significant among the three cultivars. Overall, a green-matter yield of 11-12 tons/ha per cutting (equivalent to 2.69-3.14 tons/ha dry matter per cutting) could be obtained with irrigation water having an EC of 7.8 dS/m. There was no significant difference in the salt tolerant level between the local (Hassawi cultivar) and the imported (Supreme and CUF101) alfalfa cultivars tested. The mean protein contents of alfalfa plants were 22.58% (Hassawi), 29.10% (Supreme), and 23.09% (CUF-101) irrigated with water having total salinity of 7.8 dS/m. The ranges for the mean concentrations of different macro-elements in alfalfa plants were 2.51 to 3.94% N, 0.22 to 0.44% P, and 1.48 to 3.22% K. The analyses of regression indicated a strong interaction between N, P, and K in alfalfa plants. In conclusion, there was no significant difference in biomass yield, salt-tolerant level, and the protein contents between local and the imported alfalfa cultivars irrigated with water having salinity of 7.8 dS/m. An appreciable alfalfa green forage yield of 11-12 tons/ha per cutting could be obtained under moderate saline water irrigation.