The aim of this study was to evaluate microbial activity in soils under conventional and organic agricultural system management regimes. Soil samples were collected from plots under conventional management (CNV), organic management (ORG) and native vegetation (AVN). Soil microbial activity and biomass was significantly greater in ORG compared with CNV. Soil bulk density decreased three years after adoption of organic system. Soil organic carbon (SOC) was higher in the ORG than in the CNV. The soil under organic agricultural system presents higher microbial activity and biomass and lower bulk density than the conventional agricultural system

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RESUMO

Resumo -O objetivo deste trabalho foi avaliar a influência do plantio direto, do preparo convencional do solo e de plantas de cobertura sobre indicadores biológicos associados ao ciclo do fósforo (P). O trabalho foi realizado em três áreas adjacentes, num Latossolo Vermelho-Amarelo, distribuídas da seguinte maneira: área I, dois anos de experimentação, comparando esses sistemas de plantio; área II, seis anos de experimentação e área III, Cerrado nativo. Em julho/1998 e janeiro/1999, avaliaram-se: o P da biomassa, populações de fungos e bactérias totais e solubilizadores de fosfato e a atividade da fosfatase ácida, nas profundidades de 0-5 e de 5-20 cm. A atividade da fosfatase e a ocorrência de fungos e bactérias solubilizadoras nas áreas com plantio direto foram significativamente superiores às das áreas com plantio convencional, na profundidade de 0-5 cm. O tempo de implantação acentuou as diferenças entre plantio direto e convencional quanto aos indicadores avaliados. O P da biomassa diminuiu no tratamento plantio direto com nabo forrageiro (Raphanus sativus) da área II. Os fungos solubilizadores aumentaram na presença de guandu (Cajanus cajan) e nabo forrageiro, e as bactérias solubilizadoras aumentaram na presença de guandu. O solo sob vegetação nativa apresentou maior atividade da fosfatase em relação ao das áreas cultivadas, evidenciando a importância da mineralização do P orgânico nesse ecossistema.Termos para indexação: P da biomassa microbiana, fosfatase ácida, microrganismos solubilizadores de fosfato, culturas de cobertura. Soil biological indicators associated to the phosphorus cycle in a Cerrado soil under no-till and conventional tillage systemsAbstract -The objective of this work was to evaluate the effects of no-till, conventional tillage and cover crops on biological indicators associated to the P cycle. The work was carried out on three adjacent areas on a RedYellow Oxisol: area I, a two-year experiment comparing the two management systems; area II, a six-year experiment, and area III, a native Cerrado vegetation. The soil was sampled at two depths (0-5 cm and 5-20 cm) in July/1998 and January/1999. The biological indicators evaluated were microbial biomass P, acid phosphatase activity, phosphate-solubilizing and total soil fungi and bacteria. Acid phosphatase activity and number of phosphatesolubilizing microorganisms, at the 0-5 cm depth, were significantly greater in the no-till soil, as compared to the conventional tillage. Differences between the tillage systems, regarding the biological indicators evaluated, were more pronounced in area II in which the no-till system had been established for a longer period. Microbial P decreased in the no-till Raphanus sativus treatment. P-solubilizing fungi increased in the presence of Cajanus cajan and Raphanus sativus, whereas the P-solubilizing bacteria increased in the presence of C. cajan. Highest activities of acid phosphatase were detected in the soil under native vegetation, evidencing the importance of organic P mineralization in this ecosystem.

We stand at the start of a new century that promises complexity and no let up in the scale and pace of change. Learning how to understand, adapt to and prosper in these turbulent times has become an urgent matter and a critical competence. Hence the decision to produce an issue of the European Journal of Education (EJE) that is entirely devoted to the debate around the broad directions of learning policy and practice in Europe. This publication follows two seminars that were organised in 2005, one in Glasgow (24-25 June) and the other in Paris (25-26 November) and which aimed to provide 'food for thought'. Its purpose is to raise awareness about research in the field of learning that is likely to have a significant impact on future practice, both in the formal and non-formal sectors. As an overall outcome of the exercise, we wish to ensure that this knowledge is disseminated amongst policy-makers, decision-makers and practitioners.But acting on these priorities to advance learning, using evolving theory to develop new policies is not easy. The biggest challenge remains effective implementation. As we look ahead, there are many uncertainties that tax the ingenuity and foresight of decision-makers in government, enterprise and civil society. They raise such questions as:• Can we foresee how a new generation of technologies and interfacesubiquitous, embedded and mobile -will reshape access to and delivery of learning? • Do we have the will to bridge effectively the digital divide? • How will effective lifelong learning policies and practices change the supplydemand equation? • Will the locus of learning move away from the traditional institutions of education? What will be the future roles of governments, enterprises and civil society when learning is taken out of the traditional institutions? • If it is true that brain research remains in its infancy, then how will a better understanding of the human mind influence learning in the 21 st century? • Can we expect dramatic changes in the ways we organise and transmit knowledge between generations? • Is the network society an enhanced learning society?To tackle such a vast and complex agenda lies well beyond the possibilities of one single enterprise. Rather, this issue of EJE will focus on how the learning systems