| dc.description.abstract | The aims of the study were to investigate nodulation of four
tree species namely Leucaena leucocephala, Leucaena diversifolia,
Calliandra cel.ot.trisyas and Sesbania sesban in various ecological
zones of the country. During the study Rhizobium bacteria were
isolated from nodules of the four tree legumes, characterized and
screened for their nitrogen fixing potential in potted field
soils.
Among the Rhizobium isolates 16, 14, 10 and 18 cultures were
authenticated as Rhizobium strains for L. leucocephala, L.
diversifolia, C. calothyrsus and S. sesban respectively. All the
isolates gave an acid reaction in a yeast extract mannitol agarbrornothymol
blue medium indicating they were of the fast growing
type. However, the Rhizobium isolates varied considerably in
their compatibility with the four tree species. All the 30
Leucaena isolates cross-nodulated both Leucaena spp. and C.
calothyrsus seedlings but only 17 of the isolates cross-nodulated
S. sesban. Among 10 C. calothyrsus isolates, 6 cross-nodulated L.
diversifolia and 5_ sesban while 4 cross-nodulated L. diversifolia
and S. sesban while. 4 cross-nodulated' L. leucocephala. From a
total of 18 S. sesban isolates, 9, 11 and 7 Rhizobium isolates
cross-nodulated .1. leucocephala, L . diversifolia and C.
calothyrsus respectively. However, all the isolates nodulated
their respective hosts.
Relative effectiveness varied from one isolate to the other.
Inoculation of the tree species in vermiculite using Rhizobium
isolates resulted in shoot dry matter increases ranging between
34.3 - 102.9%, 16 - 56%, 0 - 25% and 0 - 186% for L. leucocephala,
L diversifolia, C. calothyrsus and S. sesban respectively over the
uninoculated treatments. Correlation between shoot dry weight
and nodule dry weight was significant at 5% probability level in
L. diversifolia (r = 0.703) and S. sesban (r = 0.614) but was not
significant in the case of L. leucocephala (r o . 578 ) and C.
calothyrsus (r = 0.409).
In both the Kibwezi and Kabete soils used in this study
the control plants in uninoculated treatments nodulated except L.
leucocephala in the Kabete soil. Inoculation of the tree species
using Rhizobium strains resulted in shoot dry weight increases
ranging between 0 - 89%, 0 - 14%, 0 - 169.7% and 0 -86.8% for L.
leucocephala, L. diversifolia, s. sesban and C. calothyrsus
respectively over the uninoculated treaments in the Kibwezi soil.
However; plants in Kabete soil recorded shoot dry weight increases
of 0 - 48%, 0 - 54%, 0 - 15.2% and 0 - 15.1% for the four tree
species respectively. Correlation between nodule dry weight and
shoot dry weight was significant at 5%- probability level for all
the four tree species in the Kibwezi soil but was not significant
in the Kabete soil. Correlation between shoot nitrogen content
and shoot dry weight was significant at 5% probability level for
c. calothyrsus and s. sesban in both the Kabete and Kibwezi soils. | en |
