Resumo

GALVIS-SPINOLA, Arturo  e  HERNANDEZ-MENDOZA, Teresa M. Cálculo del nitrógeno potencialmente mineralizable. INCI [online]. 2004, vol.29, n.7, pp.377-383. ISSN 0378-1844.

Potentially mineralizable nitrogen (N₀) is used to compare the efficacy of new, alternative analytical techniques, as an indicator of the soil capacity for crop production, or as an indicator of the soil N supply, thus aiding in putting forward recommendations for N fertilizer application. Its importance notwithstanding, the procedure for obtaining N₀ is still controversial. This paper discusses its in vitro determination, emphasizing both conceptual and practical errors when interpreting results. It was found that the magnitude of N₀ and its mineralization rate in exponential models was dependent on the method of iterative adjustment, when an evident asymptotic distribution of accumulated mineralized N with respect to time was not obtained. This poses the risk of over-estimating N₀ and it renders unreliable the assumption that the slope is solely the result of microbial biomass activity. The findings also indicated that the rate of mineralization was not constant and that its magnitude varied during the incubation period. It was concluded that N₀ and its mineralization rate should not be calculated using just one model and that the incubation period should be divided in two parts, 0 to 5 weeks of incubation for obtaining labile N₀, and from 5 weeks onward for obtaining the N₀ found in the fractions resistant to the attack of the microbial biomass.

Palavras-chave : Modelo Exponencial; Nitrógeno Estabilizado; Nitrógeno Lábil; Tasa de Mineralización.