Diazotrophs quantification in the rhizosphere of an olive orchad (Olea europaea L.) grown in Boyacá, Colombia

摘要

The aim of this research was to determine the effect of formative pruning of olive trees in the quantity of nitrogen fixing fungi colonies and their activity in the rhizosphere of productive trees established in Sutamarchán, Boyacá. Trees in productive stage (4 years) old were selected and a complete randomized design with two treatments (pruning and no pruning) and three repetitions was used. Rhizosphere soil samples were carried out to determine the population of diazotrophs microorganisms and concentrations of NH4, NO3, CO, Fe y Mg; leaves were sampled to determine elements concentration. The statistical analysis concluded that pruning olive trees tended to increase the acidity in soil. N concentrations in soil and leaves were significantly lowest than the no-pruning trees. However, nitrogen fixing microorganisms populations were higher but with less efficiency, possibly related with the free-living fixation. The concentrations of Fe and Mg in soil, suggest a constant nitrogenase activity, but N is immobilized possibly by the microbial metabolism, lowering the possibility of being absorbed by the trees; Ca levels restricts the N nutrition. To take into account in future experiments, it's suggested to identify microorganisms populations, and measure acetylene reducing activity and the mineralization rate.