Croissance des plantules de carotte de la germination jusqu'a l'apparition des premieres feuilles

National audienc

Carbohydrate and amino acid metabolism in the Eucalyptus globulus-Pisolithus tinctorius ectomycorrhiza during glucose utilization

International audienc

Redistribution of seed reserves during the emergence of carrot seedlings and its influence on subsequent growth.

National audienc

Influence de la profondeur de semis, de l'etat de surface du sol et de la taille des semences sur la levee des plantules de carotte

National audienc

Eucalypt NADP-dependent isocitrate dehydrogenase

International audienc

Eucalypt NADP-dependent isocitrate dehydrogenase

International audienc

Comportamento compressivo de um nitossolo: efeito do tamanho de agregados, do teor de água e da pressão aplicada Compression behaviour of a clay soil: effects of aggregate size, water content and applied pressure

A compactação do solo tem sido assunto de intensivas pesquisas nos últimos anos; no entanto, os mecanismos que implicam o processo de compactação dos solos agrícolas, ainda permanecem pouco conhecidos. A contribuição do tamanho de agregados do solo, bem como o efeito do teor de água e da pressão normal aplicada na compactação e pressão de pré-compactação do solo, foi investigada em um Nitossolo Vermelho eutrófico. Amostras de solo deformado, constituídas por agregados menores que 2,5 mm e de 9,3 a 19,4 mm, foram submetidas a ensaio de compressão uniaxial drenado. O índice de vazios e a pressão de pré-compactação foram avaliados. Os resultados obtidos mostram que o tamanho de agregados teve efeito no processo de compactação do solo. A mudança da compactação do solo pode ser prevista em função do estado inicial do solo, da pressão aplicada e do teor de água.<br>Soil compaction has been the subject of intensive researches in the last ten years, but the mechanisms involved in the soil compaction process remain a little known. The contribution of aggregate size of the soil as well as the effect of water content and normal pressure applied on soil compaction and pressure of pre-compaction were investigated in a Clay soil during this trial. Disturbed soil samples constituted by aggregates less than 2.5 mm and 9.3 to 19.4 mm were submitted to a drained compression uniaxial test. The void ratio and the pre-compaction pressure were also evaluated. The results obtained show that the size of the aggregates had effect on the process of soil compaction. The change of soil compaction can be predicted according to the initial state of soil, the applied pressure and the water content of the soil

Agroecology as farmers’ situated ways of acting : a conceptual framework

International audienceThe limits of numerous agricultural systems developed on principles set after the Second World War are increasingly identified and highlighted. Meanwhile, agricultural and food systems associated with agroecological principles are progressively institutionalized in various countries. Whereas a dominant research production by agronomists consists in deduction of “agroecological practices” from fundamental agroecological principles, a gap remains between those principles and the specific management actions on farms that allow to build new agroecological framing systems. In this study, we stem from an analysis of management actions in eight different case studies corresponding to farmers’ collectives engaged in an evolution of their practices towards agroecology. We review the agroecological scientific literature to identify shared principles and system properties deduced from them, that we iteratively compared to the practices implemented by farmers, making the transition in our case studies. Our proposal is then to describe agroecology “in the making” as 4 interconnected ways of acting, each corresponding to specific relations between management actions and the systems’ properties. Lastly, the analysis of agroecology from the actors’ management practices allows us to support a new viewpoint about a research agenda for agronomists, giving reflexive benchmarks to relocate research activities within the institutionalization dynamics of agroecology