In order to explore the suitable water content of different salt soils of slfalfa in the Hetao Irrigation District

a pot experiment was carried out. Three water levels

three salt levels and one control (CK) are set up to monitor the changes of soil water storage

quality and yield of alfalfa from the bud stage to the initial flowering stage. The results showed that:(1) Plant height

aboveground biomass

underground biomass

water consumption and hay yield increased with the increase of water under the same salt conditions. But with the increase of irrigation amount

the increasing effect of irrigation on the yield of alfalfa was significantly reduced. Under the same water condition

the water consumption and the underground biomass increased with the increase of salt and then decreased. If the soil salinity was more than 3 g/kg

the water storage in the soil increased significantly

and gradually increased with the increasing irrigation amount. (2) When the soil salt content was 1~3 g/kg

water stress was beneficial to increase the content of crude protein. The content of crude protein in low water treatment was significantly higher than that in middle water and high water treatment (p<0.05). When the salt content was 3~4 g/kg

the soil salt changed the water stress threshold. The crude protein content of the treated water was significantly higher than that of the low water and high water treatment (p<0.05). Under the salt and water stress

the amino acid content of the plant increased

and the F3W1 treated amino acid content was the largest

which was 20.90%. Under the same salt condition

the amino acid content decreased stepwise with the increase of water content. Correlation analysis of each free amino acid and crude protein content showed that the correlation between glycine and methionine was not significant

but the correlation between other amino acids and crude protein was positively correlated (p<0.05). (3) When the soil salinity was in the range of 1~2 g/kg

and the water use efficiency of the water was decreasing. But when the soil salinity exceeded 2 g/kg

and the water use efficiency increased first and then decreased with the inceasing irrigation amount. When the soil salinity was 1~2 g/kg

and the water content was 70%θf~75%θf

both the yield of hay and water use efficiency were increased. When the soil salinity was 2~3 g/kg

the water content was 70%θf~85%θf

the water use efficiency was improved

the hay yield was decreased

but it is not significant. When the soil salt content was 3~4 g/kg

and the water content was above 85%θf

alfalfa production was increased. The results of this study could provide a theoretical basis for the cultivation and rational irrigation of salinized farmland.