EARLY GROWTH-RATE AND NITROGEN-FIXATION POTENTIAL IN 44 LEGUME SPECIES GROWN IN AN ACID AND A NEUTRAL SOIL FROM CENTRAL CHILE

Forty legume species, of which most were tree species of potential multipurpose value, were grown for 120 days in individual containers in an outdoor nursery, in a slightly acidic soil (pH 6.0) taken from a subhumid field site where test plantings were planned. Twenty-four species were also grown in a neutral soil (pH 7.2), taken from an arid zone field site. Dry weight of shoots, roots and nodules, as well as N2 content (DW) and nodule types were compared for all species and four provenances of the locally dominant Acacia caven. A nitrogen fixation and uptake (NFU) ratio was calculated as N2/nodules (DW). In both soil types, members of sub-family Mimosoideae nodulated more and grew faster than the Caesalpinioideae or Papilionoideae tested. Within the Mimosoideae, Acacia species, especially of sub-genus Acacia (= series Gummiferae Benth.), grew faster and accumulated more nitrogen than several Prosopis species or any other genus. In acidic soil, the local provenance of Acacia caven performed as well or better than three introduced provenances. Weedy species nodulated more consistently than non-weedy ones. Within the range tested, soil pH did not appear to affect relative performance of species and provenances tested. NFU ratios did, however, vary in the different soils. On the basis of these nursery tests, several weedy candidate species were excluded from field trials, in favor of similarly performing candidates with less potential of becoming invasive weeds.