Eucalyptus grandis (W. Hill ex Maiden) leaf traits and tree growth were studied over 3 years after the establishment of two adjacent complete randomized block designs in southern Brazil. In a nitrogen (N) input experiment, a treatment with the application of 120 kg N ha(-1) was compared to a control treatment without N addition, and in a potassium (K) input experiment a control treatment without K addition was compared to a treatment with the application of 116 kg K ha(-1). Young leaves were tagged 9 months after planting to estimate the effect of N and K fertilizations on leaf lifespan. Leaf mass, specific leaf area and nutrient concentrations were measured on a composite sample per plot every 28 days until the last tagged leaf fell. Successive inventories, destructive sampling of trees and leaf litter fall collection made it possible to assess the effect of N and K fertilization on the dynamics of biomass accumulation in above-ground tree components. Whilst the effects of N fertilization on tree growth only occurred in the first 24 months after planting, K fertilization increased the above-ground net primary production from 4478 to 8737 g m(-2) over the first 36 months after planting. The average lifespan of tagged leaves was not modified by N addition but it increased from 111 to 149 days with K fertilization. The peak of leaf production occurred in the second year after planting (about 800 g m(-2) year(-1)) and was not significantly modified (P < 0.05) by N and K fertilizations. By contrast, K addition significantly increased the maximum leaf standing biomass from 292 to 528 g m(-2), mainly as a consequence of the increase in leaf lifespan. Potassium fertilization increased the stand biomass mainly through the enhancement in leaf area index (LAI) since growth efficiency (defined as the ratio between woody biomass production and LAI) was not significantly modified. A better understanding of the physiological processes governing the leaf lifespan is necessary to improve process-based models currently used in Eucalyptus plantations.

Understanding the underlying mechanisms that account for the impact of potassium (K) fertilization and its replacement by sodium (Na) on tree growth is key to improving the management of forest plantations that are expanding over weathered tropical soils with low amounts of exchangeable bases. A complete randomized block design was planted with Eucalyptus grandis (W. Hill ex Maiden) to quantify growth, carbon uptake and carbon partitioning using a carbon budget approach. A combination of approaches including the establishment of allometric relationships over the whole rotation and measurements of soil CO(2) efflux and aboveground litterfall at the end of the rotation were used to estimate aboveground net production (ANPP), total belowground carbon flux and gross primary production (GPP). The stable carbon isotope (δ(13)C) of stem wood α-cellulose produced every year was used as a proxy for stomatal limitation of photosynthesis. Potassium fertilization increased GPP and decreased the fraction of carbon allocated belowground. Aboveground net production was strongly enhanced, and because leaf lifespan increased, leaf biomass was enhanced without any change in leaf production, and wood production (P(W)) was dramatically increased. Sodium application decreased the fraction of carbon allocated belowground in a similar way, and enhanced GPP, ANPP and P(W), but to a lesser extent compared with K fertilization. Neither K nor Na affected δ(13)C of stem wood α-cellulose, suggesting that water-use efficiency was the same among the treatments and that the inferred increase in leaf photosynthesis was not only related to a higher stomatal conductance. We concluded that the response to K fertilization and Na addition on P(W) resulted from drastic changes in carbon allocation.

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RESUMOA ocorrência de chumbo (Pb) e zinco (Zn) foram determinadas em amostras de solo e de gramíneas coletadas em três pontos de um trecho de 143 km da rodovia Presidente Dutra, entre os estados de São Paulo e Rio de Janeiro, nas distâncias perpendiculares de 0-10 m, 10-20 m, 20-35 m e 35-50 m da margem da rodovia. As concentrações de Pb e de Zn foram maiores nas amostras mais próximas da rodovia, diminuindo com o aumento da distância da rodovia, tanto nas amostras de solo, quanto nas amostras de planta. Os coeficientes de correlação entre concentração do metal no solo e concentração do metal na planta foram positivos, tanto para Pb quanto para Zn. De modo geral, as concentrações de Pb encontradas nas amostras de solo foram inferiores ao valor de referência de qualidade estabelecido para os solos no estado de São Paulo. Já para o Zn, até 10 m de distância da margem da rodovia a concentração foi superior ao valor de referência.Palavras-chave: poluição do solo, metais pesados, contaminação ambiental. Occurrence of lead and zinc in soils and plants at the margins of a highway with heavy traffic ABSTRACTThe occurrences of lead (Pb) and zinc (Zn) were determined in soil and grasses collected at three points on stretch of 143 km of the Presidente Dutra highway between the states of São Paulo and Rio de Janeiro. The soil and plant samples were collected by sampling transections perpendicular to the highway at distances of 0, 10, 20, 35 and 50 m from the highway edge. Concentrations of Pb and Zn were higher in samples closest to the highway edge, decreasing with increasing distance from the road. There were positive correlation coefficients between the metal concentration in the soil and the metal concentration in the plant. Concentrations of Pb found in soil samples were below the reference value established for the soil quality in the state of São Paulo, while for Zn, up to 10 m away from the highway edge, the concentration was higher than the reference value.

ResumoO plantio convencional no cultivo de mandioca emite gases de efeito estufa e causa a erosão do solo, declínios no rendimento e na qualidade das raízes. Comparou-se o plantio convencional (CONV) da mandioca IAC 576-70, incorporando com aração e gradagem os resíduos das culturas de cobertura: Sorgo (S), Crotalária (C), Coquetel (S+C), Brachiaria decumbens e B. ruziziensis; com o sistema de plantio direto (SPD), mediante a roçada. Sorgo e B. ruziziensis aportaram em média 3,5 t ha-¹ de matéria seca, com taxa de cobertura do solo superior a 80 %, cuja produtividade de 23,9 t ha-¹ no SPD foi 7,0 t ha-¹ inferior ao convencional; porém, equivalentes o índice de colheita (53 %), a massa fresca total e o tempo de cozimento. A colheita da mandioca no SPD aos 10 meses acumulou 63,5 t ha-¹ de fitomassa fresca, minimizando a erosão.Palavras-chave: conservação do solo, tecnologia limpa, reduções de emissões.

Agricultural crop management practices that guarantee soil quality are necessary for the sustainability of agrosystems. The use of agroforestry systems to make food production viable with less loss of soil fertility is a possible alternative for sustainable agriculture. This work evaluated the chemical characteristics of an Oxisol in three systems of use and management: 1) peach for palm heart production; 2) peach palm for fruit and seed production; and 3) Urochloa decumbens pasture. In these areas, located at Fazenda Piloto of the Agricultural Sciences Department at the University of Taubaté - UNITAU, Taubaté-SP, Brazil, samples were collected at the depths 0-10cm, 10-20cm and 20-40cm. In these soil samples, levels of P, K, Ca, Mg, B, Cu, Fe, Mn, Zn, pHCaCl2, H+Al, total organic carbon and organic carbon stock were determined. The sums of bases (SB), cation exchange capacity (CEC) and base saturation (BS) were calculated. The results were subjected to analysis of variance and the means were compared using the Tukey test at 5%. The results indicate that soil cultivated with peach palm for palm heart production showed better fertility compared to peach palm for fruit and seed production and pasture. The upper layers 0-10cm and 10-20cm are the most fertile, concentrating P, Ca e Mg, high CEC, SB and BS.