Abstract

MEYER, J; FRIGERIO, K  and  CORTES, M. Dinámica del nitrógeno mineral y la biota edáfica durante la descomposición de enmiendas orgánicas en un ambiente semiárido. RIA. Rev. investig. agropecu. [online]. 2012, vol.38, n.2, pp.196-201. ISSN 1669-2314.

The use of legumes as green manure depends on its decomposition rate and nitrogen release. The use of no tillage practice, required in fragile soils, might diminish both by not allowing a direct contact between the soil microorganisms and the residues. We studied the relationship between vetch decomposition, with and without the addition of cow manure, microbial community dynamics and Inorganic Nitrogen release in a semiarid soil of San Luis, Argentina. We incubated soils during one year, without any addition, with two different amounts of vetch with and without manure added. We also placed plastic bags containing vetch residues with and without manure, for a common decomposition study. We placed the bags in the surface and at 10 cm depth, simulating the location of residues in the two agronomic labors commonly used in the region. We took samples every three months and measured Inorganic Nitrogen, as Nitrate and Ammonium and microbial functional groups. We also withdrew and weighted bags for the decomposition study. Ammonium content in the pot soil increased from 6.7 (D1), 28 (D2), 7.3 (D3) and 26 (D4) mg/Kg in one year; the content of Nitrate increased in 17 (D1), 32 (D2), 23 (D3) and 41 (D4) mg/Kg. The increase in the inorganic Nitrogen corresponded with the evolution of ammonifiers and nitrifiers populations, confirming the strong influence of microbial succession over nutrient release in residue decomposition. Decomposition was a 20% faster in the residues placed at 20cm depth that the one on top of soil. Vetch residues liberate an important amount of Inorganic Nitrogen in the first year (even in the presence of manure and its influence over the C/N relationship and the equilibriums mineralizationimmobilization). It is recommendable a minimal tillage for a better and faster residue decomposition and nutrient liberation.

Keywords : Legumes; Decomposition; Microbial activity; Ammonium.

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