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Interactive effects of Phosphorus and salinity

It’s not enough to have phosophorus in the soil, plants have to be able to use it. A new study examines how salinity interacts with the ability to take up phosphorus.

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Soil phosphorus (P) deficiency and salinity are constraints to crop productivity in arid and semiarid regions. Salinity may weaken the effect of P fertilization on plant growth. Su and colleagues investigated the interactive effects of soil P availability and salinity on plant growth, P nutrition and salt tolerance of two alfalfa (Medicago sativa) cultivars.

Photographs of alfalfa plants grown for 75 d in a loess soil with different rates of added P and NaCl. Panels (A–D) are for ‘Golden Empress’ and panels (E–H) are for ‘Salt-tolerant Star’. Source Su et al. 2022.

A pot experiment was carried out to grow two cultivars of alfalfa in a loess soil under a combination of different rates of added P (0, 40, 80 and 160 mg P kg−1 soil as monopotassium phosphate) and sodium chloride (0, 0.4, 0.8 and 1.6 g NaCl kg−1 soil). Plant biomass, concentrations of P ([P]), sodium ([Na]) and potassium ([K]) were determined, and rhizosheath carboxylates were analysed.

There were significant interactions between soil P availability and salinity on some, but not all, of the parameters investigated, and interactions depended on cultivar. Plant growth and P uptake were enhanced by P fertilization, but inhibited by increased levels of salinity. Increasing the salinity resulted in decreased plant P-uptake efficiency and [K]/[Na]. Only soil P availability had a significant effect on the amount of tartrate in the rhizosheath of both cultivars.

Su and colleagues write: “[I]nteractions between soil P and salinity on plant growth, P nutrition and salt tolerance are complex, and the interactions depend on crop cultivar. However, increased salinity negatively affected plant P uptake and aggravated P deficiency, thus further limiting plant growth, which is often limited by P. Soil P supply affects Na uptake by plants and Na translocation within plants; appropriate application of P fertilizers can improve the salt tolerance of crops and increase their productivity in saline soils.”


Rui Su, Zekun Zhang, Chao Chang, Qi Peng, Xiao Cheng, Jiayin Pang, Honghua He, Hans Lambers, (2022) Interactive effects of phosphorus fertilization and salinity on plant growth, phosphorus and sodium status, and tartrate exudation by roots of two alfalfa cultivars, Annals of Botanyhttps://doi.org/10.1093/aob/mcab124


The Annals of Botany Office is based at the University of Oxford.

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