Aspergillus niger as a key to unlock fixed phosphorus in highly weathered soils


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Publication Details

Output type: Journal article

UM6P affiliated Publication?: Yes

Publisher: Elsevier

Publication year: 2021

Journal: Soil Biology and Biochemistry (0038-0717)

Volume number: 156

ISSN: 0038-0717

URL: https://doi.org/10.1016/j.soilbio.2021.108190

Languages: English (EN-GB)


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Abstract

Phosphorus (P) can undergo adsorption and precipitation reactions in the soil. When fixed to iron and aluminum oxyhydroxides in highly weathered soils, P is covalently linked to the soil solid phase and becomes unavailable to crops. Plants and microorganisms produce organic acids as a strategy to acquire P for growth. These compounds have been used to extract P from sparingly soluble phosphate minerals and may play a role in reverting P adsorption and fixation in the soil. The objective of this work was to study the ability of Aspergillus niger FS1 and organic acids to desorb P after 40 d of contact of the nutrient with 75-μm fractions of a typical highly weathered Oxisol. Samples of the soil fractions from the A and B horizons were incubated for 40 d with P at concentrations corresponding to 90 % of the soil maximum P adsorption capacity (MPAC). The ability of A. niger FS1 to desorb P from the soil was performed in a culture medium optimized for phosphate-solubilizing microorganisms. The desorption kinetics of the P bound to the soil fractions was evaluated for oxalic acid at 10 mmol L-1, and for a mixture of oxalic + citric acids, both at 5 mmol L-1. Water at pH 7.0 and at pH 2.0 was used as controls. The fungus released 18.0 % of the P from the A and B horizon fractions after 7 days of growth. Oxalic acid was the most efficient compound at desorbing P from the soil, releasing 32.7 % of the P from the A horizon fraction, and 18.5 %, for the B horizon fraction. These findings contribute to a better understanding of the mechanistic basis of microbial P release from highly weathered soils, opening prospects for the development of microbial techniques allowing plant access to P fixed in the soils and the improvement of P fertilizer use efficiency.


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Last updated on 2021-19-06 at 23:16