The effect of No3-N on Nodulation, dry matter yield and n2 fixed by Calliandra Calothyrsus
Abstract
Calliandra calothyrsus Meissn. is a fast- growing leguminous tree which has
been introduced to many tropical regions, including Kenya where it is used in
agroforestry systems for fu elwood, soil improvement, reforestation and fodder
production. The nitrogen fixing potential of the tree has been hampered by constraints
suchas lack of compatible rhizobia in the soil, inhibitive effects of soil mineral nitrogen
and unexploited host genotypic traits.
Two experiments were carried out to (l) screen eleven strains of Rhizobium for
N2 fixing potential in symbiotic association with C. calothyrsus and (2) assess the.
influence of inorganic N03- -N on nodulation and N2 fixed by four of C. calothyrsus
provenances. In experiment I, there were significant differences (p<O.05) between the
Rhizobium strains on the improved growth and N2 fixed by the four of C. calothyrsus
provenances. Strain effectiveness (S.E) of the eleven Rhizobium strains ranged from -
0.2% to 75.1%. Out of the three reference strains tested, only TAL 1145 gave S.E>50%.
Among the strains isolated from Kenyan soils, C.C.KARJ had the highest S.E of 65.4%
which was quite c10~~ to the best performing commercial strain TAL 1145 whose S.E
was 75.1 %. This shows that there is a large genetic variation among Rhizobium strains
which can be exploited for use in production of inoculants to improve the growth and
performance of C. calothyrsus.
In experiment 2, significant differences (p<O.05) were found between the
provenances in shoot height, root collar diameter, root and shoot dry weights.
Provenance St. Maria de Jesus from Guatemala performed best while provenance San
Ramon from Nicaragua was the worst. Increasing the soil nitrogen concentration to 99
kg N03- -N ha-1 improved the plant growth significantly (p<O.05) but did not completely
inhibit nodulation or nitrogen fixation, suggesting that C. calothyrsus was fairly tolerant
to high soil nitrate. Therefore, the current lack of nodulation by C. calothyrsus in the
soil profile under natural field conditions experienced in areas such as Embu district in
Kenya may be as a result of low population or absence of effective rhizobia rather than
mineral N.
Citation
Anditi, A.J.(1999). The effect of No3-N on Nodulation, dry matter yield and n2 fixed by Calliandra CalothyrsusSponsorhip
University of NairobiPublisher
Department of soil science, University of Nairobi
Description
Msc -Thesis