Background:

Many landscapes, both natural and anthropogenic, are dominated by degraded soils that have low phosphorus availability due to low overall phosphorus concentration or to phosphorus sequestration by iron-rich minerals.

Questions and / or Hypotheses:

Does the application of low molecular weight organic acids improve phosphorus availability and plant growth in phosphorus-poor soils, and is this effect modulated by ectomycorrhizal fungi?

Studied species / data description /Mathematical model:

Pinus pseudostrobus and its ectomycorrhiza Pisolithus arhizus, in addition to six sodium salts of organic acids.

Study site and dates:

The experiment was carried out in a shade house (35 % shade) in Morelia, Michoacán in 2015.

Methods:

We conducted experiments with Pinus pseudostrobus and its ectomycorrhiza Pisolithus arhizus in addition to six sodium salts of organic acids. Sodium salts of citrate, oxalate, acetate, tartrate, succinate and malate were added to the soil at 0, 4, 8, 16, 32 and 64 micromolar concentrations.

Results:

The salts of the organic acids-particularly tartrate and malate-solubilized phosphorus and improved plant growth after 12 months in the absence of P. arhizus. When plants were inoculated with P. arhizus, the effect of most organic acids was either detrimental or non-significant. However, citrate, tartrate and succinate improved biomass and morphological parameters.

Conclusions:

These results suggest that adding appropriate organic acids to heavily degraded soils can aid P. pseudostrobus establishment and its benefits are higher than the association with mycorrhiza for young plants during the initial stages of fungal colonization.

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