Abstract

ANRIQUEZ, Analia Liliana et al. Impact of silvopastoril systems on microorganisms related to the N cycle. Cienc. suelo [online]. 2018, vol.36, n.2, pp.117-128. ISSN 1850-2067.

The objective of this work was to evaluate the impact of the conversion of secondary forest to silvopastoral systems on the abundance of total microorganisms, microorganisms related to the nitrogen cycle, relationship with the soil N availability; in two ecological sites of the Chaco region, under different tree cover. With a completely randomized design, the "land use" factor and the "coverage" factor were studied. Land uses were: secondary forest (T), and silvopastoral of one (SP1), five (SP5) and nine years (SP9) implemented with low intensity roller-chopping (RBI) with seeding of Panicum maximun cv Gatton panic. Coverages were: Aspidosperma quebracho blanco (Qb), Schinopsis lorentzii (Qc) and Ziziphus mistol (M). Soil (Haplustol éntico) was sampled comprising the 0-15 cm depth and during the wet season. N and C of microbial biomass (Nbm and Cbm); abundance of nitrifiers (Nitr); abundance of free life N2 fixatives (Fij N₂); soluble nitrogen (Ns) and total nitrogen (Nt) were determined. The silvopastoral systems implemented through RBI: i) affected the Nbm and Cbm depending on the ecological site and the cover, ii) long-term use, regardless of ecological site, has a positive effect on the nitrifier community, and is a function of the fraction of Ns, iii) in the short and medium term use, increased Fij N₂, regardless of the coverage, while long term (SP9) the increase dependents on the coverage and is conditioned by the ecological site, iv) long term use, attenuates the effect of roller-chopping on the microbial communities related to the N cycle, therefore the vegetation cover and grazing are the main determinants of its variations, and v) to maintain the diversity of tree species and the inclusion of pastures, ensures greater heterogeneity of habitat, generating greater microbial diversity, favoring the sustainability of the soil resource.

Keywords : low intensity selective rolling; microbial biomass; tree cover; low intensity roller-chopping; microbial biomass; tree cover; Chaco region.

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