ResumoO objetivo deste trabalho foi avaliar o potencial de plantas de cobertura semeadas em diferentes sistemas de cultivo quanto à produção de fitomassa e acúmulo de nutrientes, no cerrado piauiense. O experimento foi instalado no ano agrícola 2010/2011, na Serra do Quilombo, município de Bom Jesus (Piauí). O arranjo utilizado foi em parcelas subdivididas, com os seguintes sistemas de manejo do solo: preparo convencional e plantio direto avaliados nas parcelas e, nas subparcelas, os sistemas de produção: S 1 -Soja no verão em monocultura; S 2 -Soja no verão e Penissetum glaucum na safrinha; S 3 -P. glaucum pré-soja de verão e sobressemeadura de Urochloa ruziziensis na soja no estádio R 5.5 ; S 4 -Soja de verão e sobressemeadura de P. glaucum na soja no estádio R 5.5 ; S 5 -Milho verão + U. ruziziensis simultâneo. Utilizou-se o delineamento em blocos casualizados, com quatro repetições. Os sistemas com a sobressemeadura do P. glaucum e do U. ruziziensis na soja e o consórcio de milho + U. ruziziensis destacaram-se na produção de fitomassa seca, cobertura do solo e acúmulo de nutrientes durante a entressafra no cerrado piauiense. Os nutrientes com maior taxa de acúmulo pelas plantas de cobertura foram o nitrogênio e o potássio.Palavras-chave: Braquiária, milheto, decomposição, crotalária, plantio direto. Biomass production and nutrient accumulation by cover crops in the Brazilian Cerrado of Piauí State AbstractThe objective of this work was to evaluate the biomass production and nutrient accumulation in potential cover crops sown in different cropping systems in the Brazilian Cerrado of Piauí State. The experiment was conducted in the crop season 2010/2011 in the Serra do Quilombo, county of Bom Jesus, Piauí, Brazil. This study was arranged in split plot scheme, with soil management systems (conventional tillage and no-tillage) evaluated in plots and crop systems in subplots: S 1 -Soybean monoculture in the crop-season; S 2 -Soybean in crop-season and Pennisetum glaucum for off-season; S 3 -P. glaucum before soybean crop-season and Urochloa ruziziensis oversown on soybean in the phenological stage R 5.5 ; S 4 -Soybean crop-season and P. glaucum oversown on soybean in R 5.5 ; S 5 -Maize + U. ruziziensis simultaneously in crop-season. The experimental design was in randomized blocks, with four replications. The crop systems with oversown of P. glaucum and U. ruziziensis on soybean and the consortium maize + U. ruziziensis improved the biomass production, soil coverage and nutrient accumulation during the off-season in the Cerrado from Piauí State, Brazil. The nutrients with greater accumulation rate by cover crops were nitrogen and potassium.

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Sandspur grass has hindered the integrated weed management in the Brazilian crop systems. This study aimed at evaluating the efficiency of biomass levels of different cover crops on the soil surface to control the sandspur grass. A complete randomized blocks design with four replications, in a 6 x 5 + 1 factorial arrangement, was used. The first factor consisted of six cover crops (Pennisetum glaucum-ADR 7010 and ADR 300 cultivars, Crotalaria ochroleuca, Urochloa ruziziensis, Fagopyrum tataricum and Crambe abyssinica) and the second one consisted of five biomass levels of each species (2 t ha-1, 4 t ha-1, 8 t ha-1, 12 t ha-1 and 16 t ha-1), plus a control treatment without soil cover. The variables analyzed were the total number of emerged plants, germination speed index, leaf area, root volume and shoot and root dry biomass. U. ruziziensis excelled in the suppression of C. echinatus growth by reducing the number of emerged plants, emergence speed index, shoot and root dry biomass, root volume and leaf area.

The objective of this work was to evaluate the performance of cover crops as for biomass production and nutrient accumulation during the crop off-season in an oxisol in Cerrado, in Goiás State, Brazil. The experiment was performed in Rio Verde, GO, Brazil, from November, 2007 to October, 2008. It was used a randomized block design, with plots divided according to time, with cover crops, and subplots, concerning biomass sampling, with four repetitions. The evaluated cover crops were: Brachiaria ruziziensis, Pennisetum glaucum and B. ruziziensis + Cajanus cajan, and as a reference, fallow treatment with sponteneous species. The biomass samples were collected five times, since the desiccation date of P. glaucum, 60 days after cover crop sowing, which occurred on June, 12 th , 2008. The P. glaucum has shown the greatest amount of biomass and nutrient accumulation at 60 days after sowing, while the B. brizantha, B. ruziziensis and B. ruziziensis + C. cajan have shown significant accumulation in the end of the crop off-season.

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