Abstract
ABSTRACT Soil structure, which is defined by the arrangement of the particles and the porous space forming aggregates, is one of the most important properties of the soil. Among the biological factors that influence the formation and stabilization of soil aggregates, arbuscular mycorrhizal fungi (AMF) are distinguished due to extrarradicular hyphae and glomalin production. In this context, the objective of this study was to evaluate different AMF (Acaulospora colombiana, Acaulospora longula, Acaulospora morrowiae, Paraglomus occultum and Gigaspora margarita) associated with Urochloa brizantha (A. Rich.) Stapf on soil aggregate stability. The study was conducted in a completely randomized design, using an Oxisol and autoclaved sand 2:1 (v/v), with seven treatments: five AMF; and treatments with plants without inoculation and with only the soil, with 5 replicates. The experiment was conducted during 180 days and the following variables were evaluated: mycelium total length (TML); production of easily extractable glomalin-related soil protein (GRSP) in the soil and aggregate classes; stability of the dry and immersed in water aggregates through the mean geometric diameter (MGD) and the mean weighted diameter (MWD) of aggregates; and the soil aggregate stability index (ASI). It was observed that the inoculation favored soil aggregation, with a high incidence of A. colombiana, which presented the highest MGD, TML and GRSP production in the aggregates with Ø>2.0mm and for A. colombiana and A. morrowiae in the aggregates with Ø<0.105 mm, when compared to the treatment without inoculation. These results show that there is a distinction between the effects of different AMF on the formation and stability of soil aggregates.
Highlights
Soil structure is considered one of the most important properties of soils because it exerts an essential action in soil quality maintenance, guaranteeing its greater resilience considering biotic and abiotic stresses (Rabot et al, 2018)
The inoculation with 537 UFLA showed the best results for MGDd, MGDw, total extrarradicular mycelium length (TML) and higher concentration of glomalin-related soil protein (GRSP) within the aggregates with diameter Ø> 2.0mm (Figures 1A, 1B, 1C, and Figure 2)
537 UFLA showed a higher total extraradicular mycelium (TML) with an increase of up to 32 fold when compared with the treatment without inoculation (Figure 1C)
Summary
Soil structure is considered one of the most important properties of soils because it exerts an essential action in soil quality maintenance, guaranteeing its greater resilience considering biotic and abiotic stresses (Rabot et al, 2018). Among the groups of microorganisms that play important functions in the construction of the soil structure are the arbuscular mycorrhizal fungi (AMF), which act in the formation and stabilization of the aggregates, besides contributing in terms of nutritional benefits, support to diverse stresses and promotion of growth to the plants in different phytophysiognomies (Rubin; Stürmer, 2015; Lehmann; Zheng; Rillig, 2017; Singh; Ghosh, 2018; Marinho et al, 2019). The hyphae act in the orientation of soil particles during growth on extrarradicular fungal mycelium by the “mechanical” action of pressure of the particles, forming microaggregates adjacent to the mycelia and later by the release of glomalin, which exerts an aggregating and cementing effect in the soil (Vilela et al, 2014; Rubin; Sturmer; 2015; Lehmann; Leifheit; Rillig, 2017; Kinany et al, 2018)
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