Effects of Soil Salt Stress on Phosphorus Utilization of Alfalfa
[Objective]In order to explore the effects of soil phosphorus(P)fertilizer and salt and their interaction on the plant growth,P nutrition and salt tolerance of alfalfa(Medicago sativa).[Methods]Alfalfa"Gannon Ⅶ"was planted by adding phosphate fertilizer(0,40,80,160 mg/kg,in the form of KH2PO4)and NaCl(0,0.4,0.8,1.6 g/kg)with different concentration gradients to the loess soil.[Results]The aboveground and underground biomass of alfalfa increased with the increase of P application level,but decreased with the increase of NaCl addition level.When P was added,P uptake by plants increased.When P was added at 160 mg/kg,P concentrations in roots,stems,and leaves all reached the maximum.However,the addition of salinity inhibited the absorption of P.When NaCl was added at 1.6 g/kg,P concentrations in roots,stems,and leaves all significantly decreased,when compared with that without NaCl.The content of tartrate in rhizosphere of alfalfa decreased with the increase of P compared with that without P,and the addition of exogenous salt significantly increased the content of tartrate in rhizosphere.The rhizosphere soil pH of most treatments was lower than that of non-rhizosphere pH,the decrease of soil pH under salt stress might increase the availability of soil P and P uptake by plants.A high-dose(160 mg/kg)of P significantly reduced the P-uptake efficiency of P-utilization efficiency of alfalfa.[Conclusion]In summary,there was a significant interaction between soil P fertilization and salinity,and the increase in salinity exacerbated plant P deficiency.Appropriate application of P-fertilizers can improve the salt tolerance of alfalfa and enhance its productivity in saline soils.
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