Effect of inoculation with Penicillium albidum, a phosphate-solubilizing fungus, on the growth of Trifolium pratense cropped in a volcanic soil.

Volcanic soils in the south of Chile have an elevated quantity of total P, which is scarcely available due to its high P fixation capacity. One strategy for increasing the availability of P for the vegetables that grow there would be to use phosphate-solubilizing microorganisms. In one assay conducted in a greenhouse on a volcanic soil, the effect of inoculation with Penicillium albidum, a phosphate-solubilizing fungus, was studied on the growth of red clover (Trifolium pratense L). Some chemical and biological properties of the soil were also evaluated. There were three treatments: a) active inoculum [In(+)], b) inactive inoculum (autoclaved) [In(-)] and c) without inoculum [In(0)], each one done in three replicates. The In(+) significantly (P < 0.050) increased the growth of the plants, contributing particularly to root development. The P mobilized to the shoot with In(+) was higher than twofold related to In(0) and In(-) treatments; however, the In(+) plants had similar concentration of shoot P. In the soil, available-P was not statistically different (P < 0.050) among the treatments but phosphatase activity in In(+) was higher (P < 0.050) in comparison to In(0). The results suggest that Penicillium albidum contributed to growth and nutrition of the red clover through the induction of root development and enhancing phosphate mobilization from the soil and into the plant. It is concluded that Penicillium albidum, under greenhouse conditions, in soils deficient in available P can increase the inoculation potential for volcanic soils in Chile. Anyway further studies are required, especially in organic farming where the use of soluble P fertilizer is avoided.