Effect of P application on the root nodulation of Frankia of alder (Alnus acuminata) plantations in Andisols of Costa Rica

Abstract

The effect of P application on the Frankia spp. root nodule biomass of alder trees (A. acuminata) cultivated in two soils (Typic Udivitrands at Landelina y Vista de Mar) and Entic Udivitrands (at Matinilla) was evaluated. Increasing levels of P2O5 were applied in plantations of 2, 4 and 7 years of initial age. The results showed no differences, either in theroot nodule biomass’ dry weight or in the number of active and dead nodules, with the addition of P. Nevertheless, when eliminating the site effect, an increase was observed in the number of active nodules with the addition of 61 g of P2O5 tree-1. The number of active and dead nodules dropped off with the age of the plantation. On the other hand, the root nodule biomass was high in the evaluated plantations, which constitutes an important source of organic vegetable material and of nutrients. A model was found (p=0.0001) for the prediction of the number of active nodules based on the trees’s diameter. A low correlation (r2=0.46) between diameter and the number of