Aggregation of a ferruginous nodular gleysol in a pasture area in Cuba, under the influence of Arbuscular mycorrhizal fungi associated with hybrid Urochloa

Abstract

The objective of this study was to evaluate in the field the influence of different arbuscular mycorrhizal fungi (AMF) inoculated in a pasture area of hybrid Urochloa (cv. CIAT BR 02/1752 “Caymam Pasture”) regarding the stability of aggregates of a Ferruginous Nodular Gleysol in Cuba. The experiment was conducted at the Pasture and Forage Experimental Station in Cuba (22°39′58.77″ N and 80°31′06.35″ W), using Urochloa hybrid, inoculated with three strains of AMF EcoMic® (Glomus cubense, Funneliformis mosseae and Rhizoglomus irregularis). The chosen design was in plots subdivided over time, with four treatments: three combined inoculations + non-inoculated treatment and two evaluation times (at 140 and 876 days after sowing). The number of spores, glomalin-related soil protein production, the quantification of total extraradicular mycelia, the structural stability coefficient of the soil (dry and wet) and the Soil Structural Stability Index were all evaluated. Greater stability of the aggregates was verified in dry sieving at 140 and 876 days of cultivation, however, influence of inoculation was only observed at 876 days. On the other hand, less stability was found for aggregates immersed in water. The effect of inoculation on soil aggregates can be associated with glomalin increments at 140 days, which has a cementing and cumulative character in the soil, and the length of mycelia at 876 days, which acts in the entanglement of mineral and organic soil particles, favoring the aggregation. Inoculation with AMF associated with the roots of hybrid Urochloa contributed to the best aggregate stability index at 876 days of cultivation, with an emphasis on the species G. cubense, which also showed greater competitiveness with a greater number of spores over time. Inoculation and/or soil management aimed at increasing the infectious potential of AMF is of great relevance for the formation and stability of soil aggregates in these grazing areas.