Resumen del Libro
Sustainable production of shaded coffee brings multiple benefits, including the conservation and increase of soil fertility. The objective of this study was to evaluate the capacity of biological N2 fixation of 30 different legume trees in two representative soils that include Humatas and Los Guineos series, from Puerto Rico coffee production region. The experiments were carried out in the greenhouse. Data was recorded at 90 and 180 days after planting for plant height and dry weight, nodule number and nodule dry weight and total nitrogenase activity by acetylene reduction assay (ARA). Rhizobium strains were isolated from nodulated trees, acetylene reduction assay for orthodox seeds species, and total nitrogen with Kjeldahl method for recalcitrant seeds species were conducted. The results indicated that total nitrogenase activity was higher in F. macrophylla, C. farchildiana, A. procera, E. berteroana and E. variegata. Based on the results of the ARA species, I. vera, I. fagifolia, I. spectabilis and I. quaternata, showed an important N2 fixation potential after 300 days seeding, in spite of not being included in the experimental design of orthodox seeds. From the 28 nodulated species, the ones that produced the highest amount of nodules were: C. farchildiana, F. macrophylla, I. vera, I. spectabilis, I. quaternata and A. procera. Species O. krugii and A. peregrina only nodulated in Los Guineos soil, and C. surinamensis and P. pedunculata did not nodulate at all. For future studies, tree species should be evaluated under the same experimental design, with different levels of liming and phosphorus fertilization, to improve the soil pH and plant growth.