Impacts of Rock Mineral and Traditional Phosphate Fertilizers on Mycorrhizal Communities in Pasture Plants

Intensive fertilizer use can constrain contributions from soil biological processes in pastures, including those associated with arbuscular mycorrhizal (AM) fungi. We evaluated the effect of fertilizers of different P solubility on the colonization of the roots of two common pasture plants by a community of AM fungi in a pasture soil. The treatments were a rock mineral fertilizer, a chemical fertilizer and a microbial inoculant. Subterranean clover and annual ryegrass were grown in pots for 10 weeks. Both fertilizers reduced the proportion and length of roots colonized by naturally occurring AM fungi. However, by 10 weeks, there was a much greater length of mycorrhizal root for annual ryegrass than for subterranean clover. The relative abundance of mycorrhizal fungi in the families Glomeraceae and Acaulosporaceae in roots was not affected by the form of fertilizer, but diversity indices of AM fungi in roots were altered. The chemical fertilizer had a greater negative effect on AM fungal diversity indices in the annual ryegrass roots compared with the subterranean clover roots. The reduction in OTU richness of AM fungi with fertilizer application corresponded with reduced soil pH. Differential effects of P fertilizers on naturally occurring AM fungi in this agricultural soil have the potential to influence the efficacy of P fertilizer use and dominance of plant species in grasslands.

Automated summary

Excessive fertilizer usage can limit soil biological processes in pastures, especially those related to arbuscular mycorrhizal (AM) fungi. This study examined the effect of fertilizers with different P solubility on AM fungal colonization in the roots of two common pasture plants. The results showed that both fertilizers reduced the proportion and length of roots colonized by AM fungi, but the reduction was more pronounced in subterranean clover compared to annual ryegrass. The diversity indices of AM fungi were also altered, with the chemical fertilizer having a greater negative effect on the diversity of annual ryegrass roots. The findings suggest that different P fertilizers can influence the efficacy of fertilization and dominant plant species in grasslands.