SHELF-LIFE OF LEGUME INOCULANTS IN DIFFERENT CARRIER MATERIALS AVAILABLE IN EAST AFRICA

Adoption of legume inoculation with rhizobia by small-scale farmers in East Africa, and the resultant increase in biological nitrogen fixation requires that quality inoculants meet minimum standards. BIOFIX is one of the commercially available rhizobia/legume inoculants in East Africa, whose standard is at least 109 rhizobia g-1. We examined the effect of carrier material and storage conditions on the populations of two industry standard rhizobia, Bradyrhizobium japonicum USDA 110 for soybean ( Glycine max ) and Rhizobium tropici CIAT 899 for common bean ( Phaseolus vulgaris ) over 165 days, using the drop plate method on Congo Red Yeast Extract Mannitol Agar. Viable populations of rhizobia differed significantly between carriers and rhizobia strains (P<0.05). Rhizobium tropici CIAT899, prepared with filter mud carrier, achieved a shelf-life of 135 days and B. japonicum USDA110 contained over 109 cells g-1 for 105 days. Both of these results fall below the stated six months expiry period of BIOFIX. Replacing filter mud carrier with vermiculite, resulted in an inferior product; although, both more thorough sterilisation and refrigerated storage, after a 14 day curing stage, improved the shelf-life thizobia in the inoculant packet.L\u2019adoption d\u2019inoculation de l\ue9gumineuses avec des rhizobiums par les petits producteurs en Afrique de l\u2019Est, et l\u2019augmentation de la pratique de fixation biologique d\u2019azote qui en r\ue9sulte n\ue9cessite que de bonnes qualit\ue9s d\u2019inoculum soient fournies aux producteurs. BIOFIX est l\u2019une des maisons de commercialisation d\u2019inoculum en Afrique de l\u2019Est, dont la norme minimale est de 109 cellules g-1. Nous avons examin\ue9 l\u2019effet du support et les conditions de stockage sur les populations de deux inocula de norme industrielle, Bradyrhizobium japonicum USDA 110 utilis\ue9 pour le soja ( Glycine max ) et Rhizobium tropici CIAT 899 utilis\ue9 pour le haricot commun ( Phaseolus vulgaris ) pendant 165 jours, la m\ue9thode de goutte \ue9tal\ue9e sur extrait de Congo Red Yeast Mannitol Agar a \ue9t\ue9 utilis\ue9e. Les populations de rhizobiums viables diff\ue9raient significativement d\u2019un support \ue0 un autre et d\u2019une souche de rhizobium \ue0 une autre (P<0.05). Rhizobium tropici CIAT899, pr\ue9par\ue9 avec un support en boue filtr\ue9e, assuraient la plus longue dur\ue9e de vie (135 jours) et B. japonicum USDA110 contenait plus 109 cellules g-1 pour une dur\ue9e de 105 jours. Tous ces deux r\ue9sultats sont en dessous des six mois de d\ue9lai d\u2019expiration mentionn\ue9 sur les produits BIOFIX. En rempla\ue7ant le support en boue filtr\ue9e par des vermiculites, on obtient un produit de qualit\ue9 inf\ue9rieure, malgr\ue9 que la sterilisation et r\ue9frig\ue9ration minutieuse, apr\ue8s 14 jours solidification, am\ue9liorent la dur\ue9e de vie des rhizobums dans l\u2019inoculum

Mapping the drivers of parasitic weed abundance at a national scale : a new approach applied to Striga asiatica in the mid‐west of Madagascar

The parasitic weed genus Striga causes huge losses to crop production in sub‐Saharan Africa, estimated to be in excess of $7 billion per year. There is a paucity of reliable distribution data for Striga ; however, such data are urgently needed to understand current drivers, better target control efforts, as well as to predict future risks. To address this, we developed a methodology to enable rapid, large‐scale monitoring of Striga populations. We used this approach to uncover the factors that currently drive the abundance and distribution of Striga asiatica in Madagascar. Two long‐distance transects were established across the middle‐west region of Madagascar in which S. asiatica abundance in fields adjacent to the road was estimated. Management, crop structure and soil data were also collected. Analysis of the data suggests that crop variety, companion crop and previous crop were correlated with Striga density. A positive relationship between within‐field Striga density and the density of the nearest neighbouring fields indicates that spatial configuration and connectivity of suitable habitats is also important in determining Striga spread. Our results demonstrate that we are able to capture distribution and management data for Striga density at a landscape scale and use this to understand the ecological and agronomic drivers of abundance. The importance of crop varieties and cropping patterns is significant, as these are key socio‐economic elements of Malagasy cropping practices. Therefore, they have the potential to be promoted as readily available control options, rather than novel technologies requiring introduction