Effect of vesicular-arbuscular mycorrhizae on growth nodulation and N accumulation by soybean

Abstract

The effect of vesicular arbuscular inycorrhizae on growth, nodulation and N accumulation by soybean (Glycine max (L.) Merrill) was studied in a Dard Red Latosol amended with increasing amount of super phosphate. Doses equivalent to 0 ppm, 15 ppm, 30 ppm, 60 ppm, 120 ppm and 240 ppm of P₂O₅ were applied to soil fumigated with Bromex (FUM), fumigated and infested with Glomus macrocarpum (MAC) and a non treated soil (SN). The added P and the soil treatments affected significantly all the variables evaluated. The effect of P was greater in plants colonized by G. macrocarpum. This effect was maximum when 60 ppm and 120 ppm of P₂O₅ were applied and decreased thereafter. When 60 ppm of P₂O₅ were applied, N accumulation in plants with MAC was twice as greater as in control plants with no mycorrhiza. Root colonization rates were maximum for P₂O₅ levels of 15 ppm and 30 ppm: Although the colonization rates by the native fungi reached the same level of those of MAC, the latter exhibited low effectiveness to soybean. It is concluded that application of low amounts of P combined with inoculation of G. macrocarpum can maximize growth and N accumulation by soybean growing in cerrado soil.