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There has been a growing interest in academia regarding the term 'social innovation', including in disciplines such as sociology, administration, history, management, psychology, and economics. The literature highlights the lack of scientific clarity in the use of the term, and some scholars argue that the term is no more than a 'buzzword' or a 'fad'. This article focusses on the analysis of the conceptualizations of social innovation, contrasting sociological and economical approaches, and adopts an integrative approach to propose a categorization scheme of social innovation projects based on three distinct variables, namely the level of policy support, the profit orientation and the geographical scale. We argue that government support and the scalability of social innovations should be carefully pondered depending on the characteristics of the social innovation initiatives. We conclude that policy support should privilege social innovation initiatives that, while having the potential to deliver social good, are constrained by market failures. In addition, we also argue in favour of policy support for small bottom-up initiatives that have a profit-logic but are not sufficiently robust to survive on their own due to the liabilities of smallness and newness. Finally, we advise caution in public policies supporting scale-up strategies and highlighted the inherent challenges.

RESUMO -Nos ambientes tropicais, os Cerrados destacam-se pelo seu potencial agrícola. Apesar das funções dos microrganismos no crescimento das plantas e na produtividade das culturas, existem poucas informações dos efeitos resultantes do manejo do solo, na ecologia microbiana. Neste estudo, foram avaliados os efeitos das condições ambientais e das práticas agrícolas sobre as populações bacterianas. As densidades das populações em solos com vegetação nativa foram variáveis e diferenciadas. Em Sete Lagoas, MG, as populações de actinomicetos variaram de 1,7 a 50 X 10 4 UFC/g de solo seco, enquanto em Planaltina as densidades das populações bacterianas em solo com primeiro e segundo ano de cultivo de soja foram semelhantes, mas superiores ao solo com vegetação nativa. A utilização agrícola deste solo não resultou em desequilíbrios acentuados das populações de actinomicetos provenientes de esporos e hifas. As relações esporos/hifas variaram de 1,1 a 5,8. Na rizosfera da soja, os coeficientes de correlação entre as populações de actinomicetos com as demais populações bacterianas foram significativos. Os resultados evidenciam que as práticas agrícolas utilizadas na introdução da cultura da soja em solos de Cerrados pode influenciar o equilíbrio das populações na comunidade bacteriana.Termos para indexação: actinomicetos, soja, Glycine max. DYNAMIC OF BACTERIAL POPULATIONS FROM CERRADO SOILSABSTRACT -Among tropical environments, Cerrados stand out because of its agriculture potencial. Although microorganisms play an important role on soil sustainability and crop production, few information is available on the effects of soil management systems on Cerrado s microbial ecology. In this study the effects of environmental conditions and soil management practices on bacterial populations were evaluated. Bacterial population densities in soil under native vegetation were variable and diferentiated. Actinomycetes densities varied from 1.7 to 50 X 10 4 CFU/g dry soil in Sete Lagoas region, Brazil, whereas bacterial populations in both the first and second year of land use were similar and higher than those from soil under native vegetation in the Planaltina region. Soil management practices did not cause strong modifications in the equilibrium among actinomycetes populations obtained from both spores and hyphal. The spore/hypha ratios varied from 1.1 to 5.8. Correlation coefficients among actinomycetes and other bacteria populations were signifficant in soybeans rhizospheres. Results show that soil management practices used for soybean cultivation in Cerrado soils may influence the equilibrium of bacterial populations.

In a ficld experiment on a dark-red latosol (haplustox) in the Cerrado of Brazil, green manure, including maize residues, increased yield of maize grain. Samples of soil from the experiment were investigated in the laboratory. Green manure caused no effect on amounts of phosphate extracted by Bray's solutions, nor by anion exchange resin. Adsorption measurements showed that green manure did not affect the total amount of phosphate adsorbed by the soil, in relation to the amount added nor to the concentration of phosphate in solution. However, green manure increased the proportion of added phosphate that became isotopically exchangeable so that after desorbing some phosphate in two stages, 99% of the adsorbed added phosphate was exchangeable in soil with green manure, but 89% was exchangeable in soil without it. Green manure increased the concentration of phosphate in solution that was maintained by a specific amount ofexchangeable phosphate held by the soil. Buffer power increased with time, without and with green manure; but it was less in its presence indicating that phosphate was less strongly held, and would be more mobile in soil in the field.The results indicate that easily decomposable organic material, such as green manure and crop residues, makes fertilizer phosphate more effective for crops growing in an oxisol.

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