Solubilización bacteriana de fosfatos y ensayos de inoculación de alfalfa en condiciones de invernáculo

Abstract

Phosphorus is the limiting macronutrient most important for plant
growth in the soil after nitrogen. Most agricultural soils contain large reserves
of total phosphorus, but only a small proportion of it is immediately available in
the solution. In this context, microorganisms play a fundamental role mediating
the mobilization of phosphates. The aim of this work was to study the capacity to
solubilize phosphates from diverse sources by the strains Sinorhizobium meliloti
B399, Pseudomonas fluorescens CHA0 and Bacillus sp. R19 and evaluate them in
simple and mixed inoculation trials in alfalfa. The strains used grew in all culture
media, although they did better in media supplemented with calcium. While S.
meliloti B399 showed no solubilizing activity, P. fluorescens CHA0 and Bacillus sp.
R19 showed the formation of halo of solubilization in the three culture media
where the phosphate was bound to calcium. In no case did the strains under study
form a halo of solubilization in the media where phosphorus was bound to iron
and aluminum and growth in these media was lower than that observed in those
where phosphorus was bound to calcium. The effect of the lack of availability of
soluble phosphorus on plant growth could not be reversed by simple inoculation
with S. meliloti B399 but it did occur in the treatments with P. fluorescens CHA0
and Bacillus sp. R19 and when these strains were co-inoculated with S. meliloti
B399. A mixed inoculant containing these nitrogen-fixing and phosphate-solubilizing
strains could be developed for use in agricultural practices.