Effects of Soil Salt Stress on Phosphorus Utilization of Alfalfa

Abstract

[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.

Keywords

• medicago sativa l.
• phosphorus availability
• salinity
• phosphorus-uptake efficiency
• rhizosphere tartaric acid