Differential Access to Phosphorus Pools of an Oxisol by Mycorrhizal and Nonmycorrhizal Maize

Abstract

This study investigated whether arbuscular mycorrhizal fungi (AMF) could take up phosphorus (P) from pools that are normally considered unavailable to plants. An aluminum (Al) resistant maize variety, inoculated with three species of Glomus or uninoculated, supplied with nutrient solution without P, was cultivated (90 days) in the A and B horizons of a P‐fixing Oxisol. Plant uptake of P was calculated by assessing P content of shoots and roots and correcting for seed P. Soil P fractionation was done prior to and at the end of the experiment. Phosphorus in the A and B soil horizons (∼270 mg soil kg⁻¹) was differently distributed among the pools. Nonmycorrhizal plants did not acquire any P from the soil, and all P found in the plants was from the seeds. Mycorrhizal plants depleted the inorganic Resin‐P and NaHCO₃‐P, used part of the inorganic NaOH‐P, and used neither the recalcitrant inorganic P nor the organic P fractions. Changes in plant P content matched changes in the soil P pools. Mechanisms by which maize through the mycorrhizal association acquires P are discussed. In the cultivar used, the mechanisms to cope with P deficiency and Al excess are different.

Keywords:

• Acid soil
• Al resistance
• arbuscular mycorrhiza
• maize
• P fractionation
• P fixation

Acknowledgments

We thank Willem Menkveld, Arie Brader, and Peter Pellen for help in the greenhouse, Simon Maasland for help with the preparation of the pots, and Jaap Nelemans and Willeke van Tintelen for helping in the laboratory. Sidney Netto Parentoni from Embrapa (CNPMS) is acknowledged for the maize seeds and Joe Morton (INVAM) for the inoculum of AMF. We thank Arne Janssen for commenting on previous versions of the manuscript and David Janos for stimulating discussions on the role of iron in glomalin in relation to soil P dynamics. Thanks also to CAPES, the Brazilian sponsor of Irene Maria Cardoso.