Resumo -O objetivo deste trabalho foi avaliar o efeito do manejo de plantas de cobertura na floração e na maturação fisiológica sobre a produtividade do milho cultivado em sucessão. O experimento, em delineamento de blocos ao acaso com parcelas subdivididas, foi realizado em Latossolo Vermelho, em sistema plantio direto, com nove espécies. Foram avaliados: produtividade de matéria seca; tempo de ciclagem dos resíduos vegetais; teores de N das plantas de cobertura; e produtividade de grãos e teores de N nas folhas do milho. As espécies Pennisetum glaucum, Mucuna aterrima, Cajanus cajan e Canavalia brasiliensis apresentaram as maiores produtividades de matéria seca na floração. Na maturação fisiológica, Sorghum bicolor, P. glaucum, C. brasiliensis, Crotalaria juncea e C. cajan apresentaram produtividades mais elevadas de fitomassa. Não houve efeito da época de corte e da interação planta de cobertura e época de corte sobre a produtividade do milho. As maiores produtividades de milho foram obtidos após cultivo de Urochloa ruziziensis, C. juncea, C. brasiliensis, C. cajan, P. glaucum e Raphanus sativus, e estão relacionadas ao maior acúmulo de matéria seca e ao menor tempo de ciclagem dos resíduos vegetais das plantas de cobertura.Termos para indexação: Brachiaria ruziziensis, Canavalia brasiliensis, Pennisetum glaucum, decomposição de resíduos vegetais, plantio direto, ciclagem de nutrientes. Management of cover crops at flowering and physiological maturity and its effect on maize yieldAbstract -The objective of this work was to evaluate the effect of cover crop management at flowering and physiological maturity on maize yield cultivated in succession. The experiment, in a randomized complete block design in a split-plot arrangement, was carried out on a Cerrado Oxisol under no-tillage system, with nine species. The following were evaluated: dry matter yield; turnover time of plant residues; N contents in cover crop plants; and maize grain yield and N contents in leaves. The species Pennisetum glaucum, Mucuna aterrima, Cajanus cajan, and Canavalia brasiliensis showed the highest dry matter yields during flowering. In physiological maturity, Sorghum bicolor, P. glaucum, C. brasiliensis, Crotalaria juncea, and C. cajan showed higher phytomass contents. There was no effect of mowing time and of the interaction between cover crop species and mowing time on maize yields. The highest maize yields were obtained after planting of Urochloa ruziziensis, C. juncea, C. brasiliensis, C. cajan, P. glaucum, and Raphanus sativus, and are associated with the higher dry matter yield and lower turnover time of the plant residues of the cover crop species.

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Resumo -O objetivo deste trabalho foi avaliar o efeito da adubação nitrogenada no nitrogênio da biomassa microbiana do solo (N BMS ), em diferentes profundidades, em um Latossolo Vermelho-Amarelo cultivado com cevada. O experimento foi instalado em junho de 2004, em área experimental de primeiro ano de plantio direto, anteriormente cultivada com milheto por três anos e posteriormente com soja por duas safras. Foram utilizados os seguintes tratamentos: quatro doses de nitrogênio (30, 60, 90 e 120 kg ha Microbial biomass nitrogen in cerrado soil with nitrogen fertilizer applicationAbstract -The objective of this work was to evaluate the effect of different nitrogen doses and soil depths on soil microbial biomass nitrogen (N SMB ) in a sandy textured Oxisol, cultivated with barley. The experiment was established in June, 2004, in an area which had been cultivated with millet for three years and subsequently with soya beans for two seasons. The treatments were four doses of nitrogen (30, 60, 90 e 120 kg ha -1 ) and a control without any dose. Soil samples were collected in four depths: 0-5, 5-10, 10-20 e 20-30 cm, comprising three replicates and three sampling periods: tillering, flowering and right after the harvest. The N SMB and N SMB :N total decreased according to depth. Higher doses of nitrogen did not increase the N SMB . The N total was not altered with the application of nitrogen, but it decreased with depth. There were negative correlations between the N SMB and soil pH for all the doses, except for the treatment without nitrogen. There were also positive correlations between the N SMB :N total and N SMB , but not between N SMB :N total and N total .

-The objective of this work was to evaluate the dynamics of soil microbiological attributes under integrated production systems, continuous pasture, and native cerrado. The study was conducted in a transition area from crop to livestock. Four areas with different land uses were evaluated: an integrated crop-livestockforestry system (ICLFS), cultivated with Eucalyptus urograndis alley cropping, spaced 2x2 m between plants and 22 m between alleys; an integrated crop-livestock system (ICLS

-The objective of this work was to evaluate the effect of two legumes (Crotalaria juncea and Mucuna pruriens), as cover crops, and of natural fallow, as a control treatment, on the emissions of NO x , N 2 O, and CO 2 from an Oxisol cultivated with corn, under conventional and no-tillage systems, in the Cerrado region, in Central Brazil. Variations of CO 2 fluxes in the soil were explained mainly by soil humidity and, in the legumes, under conventional system, by soil NH 4 + -N concentration. Plots with legumes under no-tillage system had higher annual emissions of CO 2 , NO x , and N 2 O than natural fallow. Results show that the use of legumes as cover crops favors the emissions of NO x -N + N 2 O-N and CO 2 -C. However, when considering the potential for mitigation of CO 2 and nitrogen oxide emissions from the soil, it is important to evaluate changes in soil carbon and nitrogen stocks.