SUMMARYAgricultural development projects frequently promote new crop production technologies for adoption at scale on the basis of research and pilot studies in a limited number of contexts. The performance of these production technologies is often variable and dependent on context. Using an example from the Agroforestry for Food Security Project in Malawi, that promoted agroforestry technologies for soil fertility enhancement, we explore the nature and implications of variation in performance across farmers. Mean effects of these technologies, measured by differences in maize yield between agroforestry and sole maize plots, were modest but positive. However, there was large variation in those differences, some explained by altitude, plot management and fertilizer use but with much unexplained. This represents risk to farmers. Those communicating with farmers need to be honest and clear about this risk. It can be reduced by explanation in terms of contextual factors. This should be an aim of research that can often be embedded in scaling up the promotion of agronomic innovations.

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The endophytic colonization, nitrogen fixation, and plant growth-promoting abilities of Herbaspirillum sp. strain B501 gfp1, which is a diazotrophic endophyte isolated from wild rice, were studied after infection (at 10 2 and 10 8 cells ml −1 ) of seedlings of cultivated rice Oryza sativa cv. Nipponbare. Both doses resulted in colonization of the roots and stem (basal stem and leaf sheath). No colonization of leaves was observed. Higher bacterial populations were observed in the roots than stems. The bacteria colonized the intercellular spaces of the root epidermis and the spaces at the junctions of the lateral roots. They also colonized the epidermis and pericycle of the basal stem and the sub-epidermal tissues of the dermal tissue system of the leaf sheath at later stages. The colonizing bacteria incorporated significant amounts of 15 N2 into the infected plants. The inoculated plants also had higher dry weights and fresh weights than the control (uninoculated) plants.

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