IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Session Details: Wednesday 30 November 2011
Concurrent Session 13 - Inoculant Quality & Application
1600 - 1740
Authors: Laetitia Herrmann 1 , Collins Majengo 2 , Edwin Mutegi 1 , Martin Kimanthi 1 , Paul Onyango 1 ,
Robert Okalebo 2 & Didier Lesueur 1,3
1 Tropical Soil Biology and Fertility institute of CIAT, World Agroforestry Center, PO Box
30677 Nairobi, Kenya.
2 Moi University, School of Agriculture and Biotechnology, PO Box 1125 Eldoret, Kenya.
3 CIRAD, UMR Eco&Sols - Ecologie Fonctionnelle & Biogéochimie des Sols &
Agroécosystèmes (SupAgro-CIRAD-INRA-IRD), 2 Place Viala, F34060 Montpellier,
France.
Presentation Title: Field evaluation of rhizobial inoculant: high nodule occupancy by the strain doesn‟t lead
to improved soybean yields in Kenya
Presentation Time: 1720 – 1740
A range of soybean commercial inoculants were tested under greenhouse and field conditions in different
locations in Kenya. One rhizobial (Legumefix) and one mycorrhizal (Rhizatech) inoculants were selected
according to the promising results obtained. The efficiency of these 2 products (single or combined inoculation)
was assessed in 150 farms in 3 mandate areas in Kenya presenting different soil characteristics and
environmental conditions. Both biomass and grain yields were measured and nodules occupancy of the rhizobial
strain was assessed by ELISA using specific monoclonal antibodies. Application of the rhizobial inoculant, alone
or in combination with the mycorrhizal product significantly increased the yields in all mandate areas (about 75%
of the farms). However, the co-inoculation didn‟t perform significantly better than the rhizobial product alone.
Controls plots gave poor results, as well as the mycorrhizal product, though that was not expected given the
good performances observed under greenhouse conditions. Nodule occupancy analysis showed that a high
number of nodules occupied by the inoculated strain did not obviously lead to an increase of soybean production.
Soil factors (pH, P, C, N…) seemed to affect the inoculant efficiency whether the strain is occupying the nodules
or not. Our statistic analysis showed that soil pH significantly affected nodulation and yield, though the effect was
variable depending on the region. P content also positively correlated with nodulation and yields. This study
provided relevant information on field efficiency of rhizobial inoculants on soybean yield in Kenya and showed
that the competitiveness of rhizobial strains might not be the main factor explaining the effect (or lack of) of
legumes inoculation in the field.
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