Resumo -O objetivo deste trabalho foi estimar as quantidades de nutrientes reciclados por cinco espécies vegetais utilizadas como culturas de cobertura do solo e que podem retornar ao solo pela mineralização da biomassa. Foram coletadas de vários experimentos amostras da matéria verde de aveia-preta (Avena strigosa Schreb), mucuna-preta (Stizolobium aterrimum Piper & Tracy), guandu (Cajanus cajan (L.) Millsp), tremoço (Lupinus albus L. e L. angustifolius L.) e ervilhaca (Vicia sativa L.). Foi estimado o rendimento de matéria seca e determinados os teores de N, P, K, Ca, Mg, Mn, Zn, Cu, e, a partir dessas concentrações, foram calculadas a média observada, a média estimada e o intervalo de confiança a 95% para cada nutriente dentro de cada classe de rendimento de matéria seca, em cada espécie vegetal. Os dados foram tabulados dentro de intervalos de classe de rendimento de matéria seca e apresentadas as quantidades estimadas de nutrientes minerais. Foram ajustadas equações para estimar as quantidades desses nutrientes. A aveia-preta e a ervilhaca reciclam grande quantidade de K, e a ervilhaca, a mucuna-preta, o tremoço e o guandu reciclam grande quantidade de N. Todas as espécies reciclam quantidades apreciáveis de Ca, Mg e micronutrientes, porém baixas quantidades de P. A rotação de culturas é um meio de implementar com sucesso o aumento das áreas de lavoura em semeadura direta.Termos para indexação: plantas de proteção, reciclagem de nutriente, mineralização, rotação de culturas. Mineral nutrients in the shoot biomass of soil cover cropsAbstract -The objective of this work was to estimate the quantity of nutrients recycled by five species of cover crops and returned to the soil after the mineralization of the biomass. Fresh samples of several experiments of black oats (Avena strigosa Schreb), black mucuna (Stizolobium aterrimum Piper & Tracy), pigeon pea (Cajanus cajan (L.) Millsp), lupin (Lupinus albus L. and L. angustifolius L.) and common vetch (Vicia sativa L.) were taken to estimate dry matter yield and determine the content of N, P, K, Ca, Mg, Mn, Zn, and Cu. From the dry matter yield, nutrient content were analyzed, and the estimated and observed mean, and a confidence limit at the 95% level, for each nutrient, in each class of dry matter yield and in each cover crop species were calculated. The data were tabulated with the corresponding dry matter class intervals and estimated quantity of nutrients. Equations were adjusted to estimate the quantity of nutrients in relation to dry matter yield. Black oats and common vetch, are good for recycling K, and common vetch, black mucuna, lupin and pigeon pea recycled large amounts of N. All species recycled large amounts of Ca, Mg and micronutrients, but small amounts of P. Crop rotation is a way of successfully increasing field areas under no-tillage.Index terms: protective plants, nutrient recycling, mineralization, rotational cropping.(1) Aceito para publicação em 16 de setembro de 2002.

A study was performed to evaluate the pH and the availability of Zn, Cu, Mn, Pb, and Ni in soil amended with increasing doses of composted solid wastes, collected in Rio de Janeiro, Rio de Janeiro State and in Coimbra, Minas Gerais State, Brazil. The influence of the time elapsed between compost application to the soil and the sampling of the plant growth substrate (soil + compost) for pH and metal availability analyses was also examined. The availability of heavy metals in the soil, in the compost and in the substrate was evaluated using DTPA solution for metal extraction. The increase of the compost doses added to the soil resulted in the increase of the pH in the substrate. The addition of the compost from the bigger city, Rio de Janeiro, resulted in higher increase in soil pH and available Zn, Cu, Pb, and Ni levels as compared to the addition of the compost from the smaller city, Coimbra. Increasing the time elapsed between the compost application to the soil and the sampling of the mixture resulted in higher available Zn, Cu, Mn, and Pb levels. The addition of the compost from Rio de Janeiro resulted in substrate metal concentrations in the order Zn > Pb > Ni > Cu > Mn and for the Coimbra compost the metal concentrations in the substrate was Zn > Pb > Cu > Ni > Mn. The higher values of pH and available metals obtained for the bigger city were attributed to the greatest metal contamination of its compost.

a b s t r a c tThe objective of this work was promote oxidation of b-glucan from oat bran with hydrogen peroxide at different concentration levels (0.3%, 0.6% and 0.9% H 2 O 2 ) and reaction times (30 and 60 min), and evaluate the physicochemical and functional properties of isedoxidised b-glucan with in-vitro tests. An increase in carbonyl and carboxyl groups and alterations in swelling power were verified in the oxidised b-glucan. The cholic acid binding capacity increased in the oxidised b-glucan; however, the fat binding capacity was not affected. After chemical digestion, the available glucose of the oxidised b-glucan was increased. Oxidation with hydrogen peroxide decreased the viscosity, hardness, adhesiveness and gumminess of the b-glucan gels. More studies are necessary to determine the effect of the oxidative treatment of b-glucan on its technological properties in food products, and biological properties should be examined with in-vivo studies.

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The ability of a rhizobacterium to protect tomato plants against naturally occurring diseases as well as to improve crop yield under field conditions was studied. The rhizobacterium was introduced to the plants through seed microbiolization. Treatments consisted of different frequencies of fungicide (Chlorothalonyl) sprayings (5, 10 or 20 applications) of tomato plants grown from either microbiolized or non-microbiolized seeds over a 90-day evaluation period. Treatment of non-microbiolized seeds without fungicide application was included as a control. The progress of the following three naturally occurring diseases was evaluated in the field and quantified: early blight (Alternaria solani), late blight (Phytophthora infestans), and septoria leaf spot (Septoria lycopersici). All treatments resulted in reduced disease severity when compared with the control treatment. Highest final fruit yields were found after treatment of plants grown from non-microbiolized seeds and sprayed with fungicide 20 times over 90 days, and for treatment of plants from microbiolized seeds that received 10 fungicide spray applications, although all treatments increased yield over that obtained in the control treatment. The results demonstrate that combined rhizobacterial and chemical treatments in the field may permit reducing fungicidal spraying frequency while at the same time increasing crop yields.