Effect of nitrogen source on some rhizospheric properties and persistence of mycorrhizal fungal propagules in an Andisol.

Resumen

Nitrogen fertilization influences plant growth and rhizospheric properties, affecting the functionality and persistence of arbuscular mycorrhizal fungi (AMF). In order to analyze the effect of two N-sources (NH4 + and NO3 -) on the persistence of AMF propagules (colonized root, mycelium and spores) and some rhizospheric parameters (pH, P available), a greenhouse experiment was carried out using two wheat (Triticum aestivum L.) cvs. Otto and Metrenco, which were grown in an Andisol. Plant biomass was determined at the dry grain stage (Zadocks 99, 150 days after sowing, DAS), the density of AMF propagules was determined three months later (240 DAS), and pH and available P were determined at both stages. The results showed that N-source and cultivar influenced most of the studied variables. The NO3 - + Metrenco combination showed the highest values for biomass, pH, available P and AMF spores (150, 13, 5 and 375% more than NH4 + + Otto interaction, respectively; p < 0.001). On the other hand, close relationships were found between biomass production and density of AMF spores (r2 = 0.89; p < 0.001), suggesting that this propagule is quantitatively affected by host plant biomass production. This propagule is probably also indirectly affected by rhizospheric conditions. This result is of a special agronomic and ecological interest in acidic soils destined to annual crops, in which nitrogen fertilization is a habitual practice, being the N-source very influential in yields.