ABSTRACT Mining is a significant driver of soil mobilization, which impacts its physical, chemical, and biological properties. Changes in land-use affect the distribution of organic matter fractions in stable aggregates, a process that is still poorly understood, especially in drastically altered areas. Recovering and monitoring soil quality to ensure the sustainable development of agricultural crops in these areas after mining is challenging. This study aimed to evaluate the influence of agronomic practices in soil rehabilitation in a bauxite-mined area after three years of field experiment installations through an assessment of organic properties in soil and aggregate classes; an attempt was also made at proposing and elaborating a Soil Quality Index (SQI), which encompasses the soil’s physical, chemical, and organic properties. Different combinations of fertilization treatments and ground cover plants intercropping with coffee were evaluated as rehabilitation practices. The results showed that after three years of rehabilitation, when organic (OF), chemical (CF), and OF+CF fertilizers were applied to the areas of coffee intercropped with Brachiaria (B), they provided higher C and N contents to the soil and aggregates classes, as well as the compartments of soil organic matter (SOM). The minimum set of soil quality indicators for reclaimed bauxite-mined areas was composed of organic indicators: labile organic carbon (LOC) and mineral-associated organic matter (C-MOM); chemical indicators including pH and effective cation-exchange capacity (t), and physical indicators such as the bulk density (BD) and stable aggregates index in water (SAIW). The t and pH were the variables most sensitive to the management systems implanted during the rehabilitation of the mined area, and, therefore, were considered the best indicators of soil quality. Brachiaria was the cover plant that contributed most to improving the soil quality of mined bauxite areas by increasing the SQI, especially when fertilized. In general, when applied to the Brachiaria, the OF+CF fertilization presented a SQI of 0.78, differing statistically from that of the natural vegetation (1.00). Fertilizers and cover crops in association with coffee in the bauxite-mined areas improved the physical, chemical, and organic properties of the soil, thus representing a viable option for reconditioning mineral exploration areas.

ABSTRACT Rational management of spontaneous plants is an alternative for increasing productivity in tree crops. This study aimed to evaluate the impact of management systems between rows and under the canopy of early dwarf cashew trees on the soil chemical properties and light-fraction organic matter and cashew root systems; we also evaluated the nutrient inputs from the spontaneous plants phytomass and cashew leaves deposited on an Arenic Kandiustults. The management systems under study were disc harrowing (DH) and mechanical mowing (MM) between rows, both with clearing under the cashew canopy (crowning), and herbicide (HERB) between the rows and under the canopy (without crowning). Soil and plant samples (leaves, stems, and roots) were collected at three points: under the canopy, at the canopy projected limit, and between the rows of cashew plants, all after seven years of conducting the experiment. Soil samples collected at the layers of 0.00-0.05, 0.05-0.10, 0.10-0.20, and 0.20-0.30 m were evaluated for total organic carbon, light-fraction organic matter, and chemical attributes. Dry matter, Na, Ca, Mg, N, P, and K were determined in the spontaneous-plant phytomass from under the canopy, at the canopy projected limit, and between the rows. Results showed that between rows of cashew trees there are higher phytomass input and increases in the light fraction of organic matter, pH and Mg2+ in the soil in the treatment MM. Not removing crop residues or spontaneous plants by crowning promoted accumulation of organic material and higher contents of nutrients under the canopy. The management of spontaneous plants and also soil surface under the canopy of the cashew plants had a great influence on productivity. The crowning, used in MM and DH, led to lower productivity, 1,171.87 and 594.97 kg ha-1, respectively, when compared with the absence of crowning (HERB), which resulted in productivity of 1,363.80 kg ha-1. The practice of crowning is not recommended for soil management systems in dwarf cashew crops.

Abstract The biota of the humid mountain ranges of the Brazilian semiarid is still poorly understood. In order to fill this scientific gap, we carried out an extensive survey along altitudinal ranges (400m - 1,000 m) on both the windward and the leeward slopes of the Baturité Mountain Range, in the state of Ceará state. We registered 400 plant species and 92 families. The Myrtaceae (36 spp.), Fabaceae (25 spp.), Rubiaceae (20 spp.) and Bromeliaceae (15 spp.) families predominated on the windward slope; while Fabaceae (19 spp.), Myrtaceae (14 spp.) and Euphorbiaceae (11 spp.) were the most abundant on the leeward slope. As we expected, the species richness of trees, shrubs, subshrubs, epiphytes and terrestrial herbs was positively correlated with the altitude (R2 > 0.60). Above 800 m, we registered 273 species exclusive to the windward slope, 81 exclusive to the leeward slope, and 46 shared species. Therefore, management actions must consider the spatial heterogeneity, distribution and taxa richness.

ABSTRACT Forest cover in areas degraded by mining is an alternative way of mitigating CO2 concentrations in the atmosphere by fixing C in tree biomass. This study evaluated the growth and C stocks of forest cover in an area of bauxite mining with four sources of fertilizer. Height (Ht), diameter at ground level (DGL), and diameter at breast height (DBH) were determined in Anadenanthera peregrina (Ap), clonal Eucalyptus (Euc), and a mixed plantation of 16 native forest species (Nat) at 6, 18, 36, and 56 months of age. Trunk+bark volume, biomass, and C stock were also determined for these forest covers at 56 months of age. The fertilization treatments were a standard (SF) adopted by the company, SF plus organic fertilizer (OF), chemical fertilizer (CF), and OF+CF. Euc displayed greater values of Ht, DGL, and DBH under OF+CF and OF. Fertilization did not influence the Ht and DBH of Ap, but DGL was higher under OF+CF at 36 months compared to SF. The Ht values of Nat were influenced by fertilization at 18 months, with the lowest values under SF. The fertilization influenced the DGL of Nat at 36 and 56 months, which did not occur with DBH. The pioneer species had higher Ht, DGL, and DGB compared to non-pioneer species, regardless of the type of fertilization studied. Fertilization influenced the Ht and DGL of pioneer species at 18 and 36 months of age and only the Ht of non-pioneer species. The estimates of Euc biomass (255 Mg ha-1) and C stocks (120 Mg ha-1) under OF+OC were four times greater than in Ap and Nat, which showed no difference between themselves or the types of fertilization. The growth and estimates of volume, biomass, and C stocks of the forest cover were comparable to those of unmined areas. Euc had the greatest growth, biomass, and C stocks.

RESUMO: Irrigação com água produzida, que é gerada durante a extração de petróleo bruto e gás pode ser uma opção para agricultura irrigada em regiões semi-áridas mas o efeito desta água tratada no estado nutricional das plantas e no crescimento e desenvolvimento das culturas deve ser avaliado. Com esse propósito, determinamos alterações nos aspectos nutricionais da cultura de girassol irrigado com água produzida e os efeitos na produção de biomassa e de grãos de girassol. O girassol cv. BRS 321 foi cultivado durante três ciclos em áreas irrigadas com água produzida filtrada (FPW) e tratada por osmose (OPW) e água subterrânea (GW). Ao final de cada ciclo, raízes, parte aérea e grãos foram coletados para determinar as concentrações de nutrientes. Irrigação com água produzida afetou o acúmulo de nutrientes em plantas de girassol. Irrigação com OPW promoveu acúmulo de Ca, Na, N, P e Mg. Plantas irrigadas com FPW acumularam maiores teores de Na em raízes e parte aérea, e afetou negativamente a produção de biomassa e de grãos de girassol. Os níveis de Na na parte aérea de plantas irrigadas com FPW aumentaram ao longo dos três ciclos de cultivo. Sob condições controladas, é possível reutilizar a água produzida tratada por osmose inversa na agricultura, mas necessita de mais estudos a longo prazo para compreender o efeito cumulativo, nas propriedades químicas e biológicas do solo e na produção das culturas. Estes resultados sugerem que a irrigação com água produzida tratada adequadamente, é uma boa estratégia para a sustentabilidade dos recursos hídricos.

ABSTRACT: Irrigation using produced water, which is generated during crude oil and gas recovery and treated by the exploration industry, could be an option for irrigated agriculture in semiarid regions. To determine the viability of this option, the effects of this treated water on the nutritional status of plants should be assessed. For this purpose, we examined the nutritional changes in sunflowers after they were irrigated with oil-produced water and the effects of this water on plant biomass and seed production. The sunflower cultivar BRS 321 was grown for three crop cycles in areas irrigated with filtered produced water (FPW), reverse osmosis-treated produced water (OPW), or ground water (GW). At the end of each cycle, roots, shoots, and seeds were collected to examine their nutrient concentrations. Produced water irrigation affected nutrient accumulation in the sunflower plants. OPW irrigation promoted the accumulation of Ca, Na, N, P, and Mg. FPW irrigation favored the accumulation of Na in both roots and shoots, and biomass and seed production were negatively affected. The Na in the shoots of plants irrigated with FPW increased throughout the three crop cycles. Under controlled conditions, it is possible to reuse reverse osmosis-treated produced water in agriculture. However, more long-term research is needed to understand its cumulative effects on the chemical and biological properties of the soil and crop production.

Objetivou-se conhecer a contribuição de sistemas agroflorestais (SAFs) e tradicionais para o sequestro de carbono e a reserva de nutrientes presentes nas plantas, serrapilheira e solo. O estudo foi realizado na região semiárida brasileira, em experimento de longa duração realizado na Fazenda Experimental da Embrapa Caprinos e Ovinos. Estudaram-se dois sistemas agroflorestais: agrossilvipastoril (ASP) e silvipastoril (SP) e um tradicional (AG), sendo também utilizadas duas áreas sob pousio após o manejo tradicional (seis anos - F6 e nove anos F9) e uma área de Caatinga conservada (CAT). Nessas áreas, foram realizadas coletas de solo, serrapilheira e plantas, sendo os teores de C, N, P, K, Ca e Mg quantificados em cada um desses compartimentos. Os SAFs (ASP e SP) apresentaram estoques de nutrientes superiores ao tradicional e intermediários em relação à Caatinga conservada. No ASP, grande parte dos nutrientes extraídos pelas colheitas volta ao sistema por meio das entradas via serrapilheira, capinas das herbáceas e poda das leguminosas. Os estoques no solo, na serrapilheira e nas plantas herbáceas após os períodos de pousio de seis e nove anos foram semelhantes à Caatinga conservada, porém os estoques do estrato arbóreo foram inferiores à condição natural.

This study evaluated the contribution of agroforestry (AFS) and traditional systems to carbon sequestration and nutrient reserves in plants, litter and soil. The study was carried out in the semiarid region of Brazil in a long-term experiment on an experimental farm of the goat and sheep section of the Brazilian Agricultural Research Corporation (Embrapa). Two agroforestry systems were investigated: agrosilvopastoral (ASP) and forest-pasture areas (SP) as well as traditional agriculture management (TM), two areas left fallow after TM (six fallow years - F6 and nine fallow years - F9) and one area of preserved Caatinga vegetation (CAT). Soil, litter and plants were sampled from all areas and the contents of C, N, P, K, Ca and Mg per compartment determined. The AFS (ASP and SP) had higher nutrient stocks than the traditional and intermediate stocks compared to the preserved Caatinga. In the ASP, a relevant part of the nutrients extracted by crops is returned to the system by constant inputs of litter, weeding of herbaceous vegetation and cutting of the legume crops. After fallow periods of six and nine years, carbon and nutrient stocks in the compartments soil, litter and herbaceous plants were similar to those of the preserved Caatinga (CAT), but still lower than under natural conditions in the woody vegetation.

O objetivo deste trabalho foi avaliar o efeito das árvores de pau-branco (Cordia oncocalyx) sobre parâmetros fisiológicos, altura e biomassa do milho, em diferentes distâncias das árvores, em sistema agrossilvipastoril. Utilizou-se o delineamento experimental de blocos ao acaso, com quatro tratamentos (distâncias do caule das árvores de 1, 2, 3 e 4 m), além do controle (plantas do cultivo tradicional), e cinco repetições. Cada parcela consistiu de uma árvore de pau-branco, ao centro, e linhas de milho plantadas nas quatro distâncias avaliadas do caule. As medidas fisiológicas e a produção de matéria seca foram registradas aos 30, 60 e 90 dias após o semeio do milho. As plantas sob a copa do pau-branco, a 1 e 2 m do caule, tiveram suas trocas gasosas, altura e produção de matéria seca afetadas pelas árvores. As plantas cultivadas a 3 m do caule tiveram desempenho semelhante ao observado no cultivo tradicional, e as cultivadas a 4 m apresentaram maior fotossíntese, condutância estomática, transpiração, altura e produção de matéria seca. As plantas de milho sob a copa são afetadas negativamente pelo sombreamento das árvores, enquanto as plantas fora da copa podem se beneficiar da presença das árvores no sistema.

The objective of this work was to evaluate the effect of "pau-branco" (Cordia oncocalyx) trees on physiological parameters, height, and biomass of maize at different distances from the trees in an agrosilvipastoral system. The experimental design was a randomized complete block with four treatments (distances from trees of 1, 2, 3, and 4 m), besides a control (plants cultivated in the traditional system), and five replicates. The plots consisted of one "pau-branco" tree at the center, and maize rows planted at the four evaluated distances from the tree stem. Physiological measurements and dry matter production were recorded at 30, 60, and 90 days after the sowing of maize. The plants under the canopy of "pau-branco" - at 1 and 2 m from the stem - had their gas exchange, height, and dry matter production affected by the trees. The plants 3 m away from the stem had similar performance to those in the traditional system, and the plants at 4 m of distance had higher photosynthesis, stomatal conductance, transpiration, height, and dry mass production. Maize plants under the canopy are negatively affected by tree shading, whereas plants outside the canopy can be favored by the presence of trees in the system.

Práticas conservacionistas são importantes na melhoria da proteção ambiental de agroecossistemas em regiões semiáridas por estes serem considerados ambientes frágeis. Indicadores de qualidade do solo são elementos úteis na avaliação do impacto de algumas práticas de manejo agrícola e a utilização de indicadores reconhecidos e possíveis de serem mensurados por agricultores é uma abordagem inovadora que busca integrar conhecimento científico e local. Este estudo objetivou avaliar o impacto de algumas práticas de manejo em áreas de agricultores familiares que utilizam consórcios agroecológicos através de indicadores de qualidade do solo relacionados à estrutura do solo. Estes indicadores foram apontados como importantes pelos próprios agricultores, sendo propostas metodologias para aplicação em campo por eles mesmos, que foram posteriormente comparadas com aplicações em laboratório. Os indicadores utilizados foram resistência do solo à penetração, estabilidade e dispersão de agregados para áreas sob consórcio agroecológico e vegetação natural. Pode-se concluir que os consórcios agroecológicos contribuem para a conservação da estrutura do solo e o envolvimento dos agricultores é uma importante parte do desenvolvimento da pesquisa.

Conservation practices are important in improving the environmental protection of agroecosystems in semiarid regions, as these are considered to be fragile environments. Soil-quality indicators are useful elements in evaluating the impact of some agricultural management practices, and the use of recognized indicators which are able to be measured by farmers is an innovative approach that seeks to integrate both scientific and local knowledge. This study aimed to evaluate the impact of various management practices through indicators of soil quality related to soil structure, in areas of family farming where agroecological consortiums are employed. These indicators were identified as important by the farmers themselves, and methodologies were suggested for field application by the farmers, which were later compared to applications made in the laboratory. The indicators used were penetration resistance of the soil and stability and dispersion of aggregates for areas of agroecological consortium and natural vegetation. It can be concluded that agroecological consortia contribute to the conservation of soil structure and that the involvement of farmers plays an important role in developing research.

Na região semiárida, o manejo inadequado dos sistemas de cultivo, aliado à baixa produção de fitomassa, pode contribuir para reduzir os estoques de carbono (C) e nitrogênio (N) do solo; portanto, a adoção de sistemas de manejo para a preservação desses elementos é necessária. Objetivou-se avaliar as alterações promovidas nos estoques de C e N do solo por sistemas agrícolas agroflorestais (agrossilvipastoril e silvipastoril) e tradicional (com derrubada da vegetação, queima e cultivo por dois-três anos), confrontando-os à vegetação natural de Caatinga, após 13 anos, em experimento instalado em um Luvissolo Crômico órtico típico, no município de Sobral, Ceará. Amostras de solo foram coletadas nas profundidades de 0-6, 6-12, 12-20, 20-40 e 40-60 cm, em quatro repetições, considerando os relevos plano, convexo e côncavo em cada situação de estudo, sendo determinados o C orgânico total, o N total e as densidades do solo. Entre os sistemas agroflorestais estudados, o silvipastoril, em longo prazo, promoveu as maiores reduções nos estoques de C e N, enquanto o agrossilvipastoril as menores perdas, representando alternativa sustentável para o sequestro de C e N do solo nessas condições semiáridas. O sistema de cultivo tradicional apresentou reduções de 58,87 e 9,57 Mg ha-1 dos estoques de C orgânico e N total, respectivamente, indicando sua não adequação para as condições semiáridas brasileiras. Os relevos côncavo, no sistema agrossilvipastoril, e plano, no silvipastoril, apresentaram os maiores estoques de C orgânico, enquanto para o N total, a forma côncava apresentou os maiores valores na vegetação nativa, agrossilvipastoril e silvipastoril.

In the semiarid region of Brazil, inadequate management of cropping systems and low plant biomass production can contribute to reduce soil carbon (C) and nitrogen (N) stocks; therefore, management systems that preserve C and N must be adopted. This study aimed to evaluate the changes in soil C and N stocks that were promoted by agroforestry (agrosilvopastoral and silvopastoral) and traditional agricultural systems (slash-and-burn clearing and cultivation for two and three years) and to compare these systems with the natural Caatinga vegetation after 13 years of cultivation. The experiment was carried out on a typical Ortic Chromic Luvisol in the municipality of Sobral, Ceará, Brazil. Soil samples were collected (layers 0-6, 6-12, 12-20, 20-40 and 40-60 cm) with four replications. The plain, convex and concave landforms in each study situation were analyzed, and the total organic C, total N and densities of the soil samples were assessed. The silvopastoral system promoted the greatest long-term reductions in C and N stocks, while the agrosilvopastoral system promoted the smallest losses and therefore represents a sustainable alternative for soil C and N sequestration in these semiarid conditions. The traditional agricultural system produced reductions of 58.87 and 9.57 Mg ha-1 in the organic C and total N stocks, respectively, which suggests that this system is inadequate for these semiarid conditions. The organic C stocks were largest in the concave landform in the agrosilvopastoral system and in the plain landform in the silvopastoral system, while the total N values were highest in the concave landform in the native, agrosilvopastoral and silvopastoral systems.

Physiological differences in the Cordia oncocalyx tree growing at different densities in two distinct areas were investigated. An agrosilvopastoral system (AGP) and a secondary forest (SF) were studied. Under both types of land-use, C. oncocalyx presented a relative frequency of approximately 50%, and absolute densities of 670 and 80 individuals per hectare, respectively. Net photosynthesis (A), stomatal conductance (g s), and transpiration (E) were measured, and the SPAD index was recorded in sun leaves from the canopy and shade leaves from the lower canopy, in both the wet and dry seasons. We quantified the dry biomass of leaves and fruit on a per-tree basis at the end of the wet season. Net photosynthesis was higher in shaded leaves in the AGP in the wet season, reaching an average of 4.8 μmol m-2 s-1 against 3.2 μmol m-2 s-1 under SF. As trees began to shed their leaves at the beginning of the dry season and more radiation reached the shaded leaves, there was an increase in SF for A, depending on the intensity of light reaching the leaves. In the sun leaves, gas exchange was similar for the land-use systems during the wet season, but stronger in AGP than under SF during the dry season. This happened when the leaves in AGP retained more relative water content during a period of low gravimetric levels of the soil water. The lower tree density in AGP promoted a higher SPAD index and dry biomass in both the sun and shaded leaves, and allowed greater A, E and g s rates in the sun leaves at the beginning of the dry period.

Objetivou-se avaliar o efeito da irrigação localizada sobre a granulometria, pH e teores de nutrientes de um Neossolo Quartzarênico cultivado com coqueiro anão em área de perímetro irrigado no estado do Ceará. O estudo foi conduzido no campo experimental da Embrapa Agroindústria Tropical/CNPAT, situado no município de Paraipaba, CE. Foram selecionadas e amostradas duas áreas sob fertirrigação utilizando microaspersores do tipo difusor e rotativo. Comparações foram feitas entre pontos definidos na área sob influência da irrigação e pontos fora da área de alcance do microaspersor. Amostras de solo foram coletadas nas distâncias horizontais de 0,30; 0,60; 0,90; 1,20; 1,50; 1,80; 2,10; 2,40 e 2,70 m a partir da planta, nas profundidades de 0-10; 10-20; 20-30; 30-40 e 40-50 cm. Foram quantificados os teores de areia, silte e argila; os teores de Ca2+, Mg2+ e K+ trocáveis, P disponível, pH e a condutividade elétrica do extrato de saturação. Na área do emissor tipo difusor ocorreu aumento significativo de 1% nos teores de argila em subsuperfície, o que pode estar associado ao processo de dispersão das argilas pela presença de Na+ trocável na água de irrigação. A irrigação favoreceu acúmulo de Ca2+, Mg2+ e P disponíveis nas proximidades dos microaspessores em superfície, e de Na+ em profundidade. O acréscimo de Na+ em profundidade implica em um potencial risco de salinização, sugerindo que o manejo da irrigação deve considerar não somente o tipo de microaspersor, mas especialmente a qualidade da água de irrigação e as características físicas e químicas do solo.

The objective of this study was to evaluate the effect of located irrigation on the soil granulometry, pH and nutrient contents of a Quartzipsamments soil cultivated with dwarf coconut. The study was conducted at the experimental station of Embrapa Agroindústria Tropical/CNPAT, located at Paraibapa County, state of Ceará, Brazil. Two areas under fertirrigation using two models of microsprinklers (diffuser and rotative) were selected. Comparisons were made between irrigated area and non-irrigated area. Soil samples were taken from horizontal distances of 0.30; 0.60; 0.90; 1.20; 1.50; 1.80; 2.10; 2.40 e 2.70 m from each plant in the 0-10; 10-20; 20-30; 30-40 e 40-50 cm layers. The measured soil variables were sand, silt and clay contents; available Ca2+, Mg2+, K+ and P; pH and soil electrical conductivity. In the area adopting diffuser microsprinkler occurred an increase of 1% in the clay content at the soil subsurface, which may be attributed to clay dispersion process due to the presence of available Na+ ions in the irrigation water. The fertirrigation favored accumulation of Ca2+, Mg2+ e P at the neighborhood of the microsprinklers in the soil surface, and increase of available Na+ in the deeper soil layers. The increase of Na+ in the soil profile suggests the increase of potential hazard of soil salinization, thus the management of irrigation must consider not only the type of microsprinkler but also the quality of water used in the irrigation associated to the soil physical and chemical properties.

Estudos comprovam que na região semiárida cearense sistemas agroflorestais aumentam os teores de C orgânico do solo. Entretanto, não há registro se tal incremento implica também mudanças qualitativas nos diferentes compartimentos da matéria orgânica do solo. O objetivo deste estudo foi verificar possíveis alterações das características químico-estruturais das frações ácidos fúlvicos e ácidos húmicos de um Luvissolo em áreas sob sistemas agroflorestais, cultivo intensivo e vegetação nativa em experimento de longa duração, instalado na região semiárida cearense. O estudo foi conduzido no campo experimental do Centro Nacional de Pesquisa de Caprinos da EMBRAPA, município de Sobral-CE, onde foram avaliados os seguintes tratamentos: agrossilvopastoril (AGP), silvopastoril (SILV), cultivo tradicional intensivo em pousio (CIP) e áreas sob mata nativa (MN). As frações ácidos fúlvicos (AF) e ácidos húmicos (AH) foram extraídas das camadas de 0-6 e 6-12 cm e caracterizadas por meio das análises de composição elementar, termogravimetria e espectroscopia na região do infravermelho. A análise da composição elementar da fração AH confirma o comportamento dos dados da fração AF, mostrando redução dos teores de C, H e N e aumento do teor de O nos tratamentos AGP e CIP em relação aos sistemas SILV e MN. A fração AH apresentou maiores percentuais de perda de massa na região de maior estabilidade térmica (350-600 °C) em todos os tratamentos, à exceção do SILV na camada de 0-6 cm. A despeito da similaridade entre os espectros de infravermelho, no tratamento SILV a fração AF extraída da camada de 6-12 cm sofreu diminuição das bandas de absorção em 1.708 e 1.408 cm-1, seguida de aumento da banda de absorção em 1.608 cm-1, atribuída a grupamentos aromáticos C = C. Tal comportamento sugere o aumento do caráter aromático da estrutura. Os sistemas AGP e CIP, por promoverem maior revolvimento do solo, favorecem a permanência de substâncias húmicas de maior caráter aromático em comparação com os sistemas SILV e MN. O menor caráter aromático das substâncias húmicas do solo no sistema SILV implica aumento dos sítios de troca da matéria orgânica do solo, implicando na melhoria da ciclagem de nutrientes e na manutenção do processo produtivo do sistema.

Studies have proven that the agroforestry systems in the semi-arid region of the State of Ceará, Brazil, induce an increase in soil organic C levels. Notwithstanding, there is no information if this increase also results in qualitative changes in different pools of soil organic matter. The objective of this study was to verify the possible chemical and structural alterations in fulvic and humic acids of a Luvisol in areas adopting agroforestry, traditional intensive cultivation and native forest in a long-term experiment conducted in the semi-arid region of Ceará State, Brazil. The study was conducted in an experimental area of the National Goat Research Center (Embrapa) in Sobral, CE. The following treatments were evaluated: agrosilvopasture (AGP), silvopasture (SILV), intensive cultivation under fallow (ICF), and areas with native forest (NF). Soil fulvic and humic acids fractions were extracted from the 0-6 and 6-12 cm layers and characterized by elemental composition, thermogravimetry and infrared spectroscopy analyses. The elemental composition analysis of humic acids confirmed the data found for fulvic acids, showing reduction in the C, H and N levels, followed by an increase in O contents in the AGP and ICF treatments over SILV and NF. In all treatments, except to SILV in the 0-6 cm layer, the percentage of mass loss was highest (300-600 °C) for humic acids in the thermally most stable region. Despite the similarity between infrared spectra, soil fulvic acids in the SILV treatment extracted from 6-12 cm depth decrease the absorption bands at 1708 and 1408 cm-1 followed by an increase in the absorption band at 1608 cm-1 attributed to aromatic C=C groups. This behavior suggests an increase in the aromatic character of the structure. The AGP and ICF treatments, which increase the soil tilling, favored the maintenance of humic substances with a more aromatic character in the soil than SILV and NF. The less aromatic humic substances in the SILV treatment resulted in an increase of exchange sites of soil organic matter, indicating improved nutrient cycling and maintenance of productivity in the system.

O estudo teve por objetivos: (a) avaliar a produção de biomassa proveniente da copa do cajueiro-anão precoce, clone CCP 76, com idades de 2, 3, 8 e 9 anos de implantação da cultura; (b) determinar a taxa de decomposição das folhas; e (c) quantificar a contribuição de nutrientes potencialmente disponíveis na biomassa para serem reciclados no solo. O trabalho foi conduzido no Campo Experimental do Curu, no Município de Paraipaba, CE, no período de dezembro de 2003 a janeiro de 2005. Os tratamentos constituíam de pomares com 2, 3, 8 e 9 anos de implantação, distribuídos em delineamentos inteiramente casualizados com oito repetições. Para a coleta da serapilheira, utilizaram-se coletores de 1 m² com malha de 1 mm² colocados a 40 cm da superfície do solo. Após a coleta, o material foi separado em frações: folhas, galhos, inflorescência, pedúnculo e castanha, que após secadas em estufa foram pesadas. Na fração folhas, determinaram-se os teores de N, P, K, Ca, Mg, S, Na, Cu, Fe, Mn e Zn. De cada planta, coletaram-se folhas prestes a cair, para determinar a taxa de decomposição. Utilizaram-se 12 g desse material seco em estufa, o qual foi colocado em bolsas de náilon com 20 x 20cm e malha de 2mm, as quais foram distribuídas na superfície do solo e coletadas após 112, 233 e 369 dias. Em cada coleta, o material foi seco em estufa, determinando-se as quantidades remanescentes de biomassa e de nutrientes (N, P, K, Ca, Mg, S, Na, Cu, Fe, Mn e Zn). As plantas com 8 e 9 anos de implantação depositaram maiores quantidades de serapilheira durante o período do experimento e apresentaram os maiores potenciais de reciclagem de nutrientes. Durante o período do experimento, observou-se, de modo geral, que o processo de decomposição foi rápido nos primeiros quatro meses e, posteriormente, manteve-se lento até o término das observações. No cajueiro, a maior parte dos nutrientes foi liberada nos primeiros quatro meses de decomposição das folhas.

This study aimed to (a) to evaluate the biomass production from the crown of the young dwarf cashew, clone CCP 76, at 2, 3, 8 and 9 years of culture implantation, (b) to determine the rate of leaf decomposition and (c) to quantify nutrient contribution potentially available in the biomass to be recycled into the soil. The research was conducted at the Experimental Field of Curu, in Paraipaba - CE, from December, 2003 to January, 2005. The treatments consisted of orchards with trees of 2, 3, 8 and 9 years of plantation, distributed in a completely randomized design with eight replications. Litter was collected using 1 m² collectors with 1 mm² mesh place 40 cm above the soil surface. After sampling, the material was sorted out into portions of leaves, branches, inflorescence, peduncle and nut, oven dried and weighed. In the leaf portion, the compositions of N, P, K, Ca, Mg, S, Na, Cu, Fe, Mn and Zn were determined. Leaves ready to fall were collected from each plant to determine their decomposition rate and 12 g of this material was stove dried, and placed in 20 cm x 20 cm nylon bags and 2 mm mesh which were distributed on the soil surface and collected after 112, 233 and 369 days. In each collection, the material was oven dried and the remaining nutrient biomass (N, P, K, Ca, Mg, S, Na, Cu, Fe, Mn and Zn) was determined. The 8- and 9- year- old plants deposited greater quantities of litter during the experimental period and showed greater potential for nutrient recycling. During the experimental period it was generally observed that the decomposition process was fast in the first four months, remaining slow until the end of the observation period. Most of the nutrients in the cashew tree were released in the first four months of leaf composition.

Os sistemas agroflorestais têm sido amplamente promovidos como sistemas de produção agrícola sustentáveis, principalmente para regiões subdesenvolvidas, onde o uso de insumos externos é inviável. Este trabalho objetivou avaliar o impacto de quatro sistemas agroflorestais e um sistema convencional sobre os teores de N total, mineral e em diferentes frações orgânicas, após cinco anos de uso de um Luvissolo na região semi-árida cearense, em experimento instalado na Embrapa Caprinos, em Sobral (CE). Os sistemas testados foram: agrossilvipastoril (AGP); silvipastoril (SILV); tradicional cultivado em 1998 e 1999 (TR98); tradicional cultivado em 2002 (TR02); cultivo convencional (CC); e uma área de Caatinga (CA). Nas amostras de solo, avaliaram-se os teores de N total, N-NH4+, N-NO3-, N microbiano, N da matéria orgânica leve (livre e oclusa) e o N das substâncias húmicas. Os resultados indicaram que todos os tratamentos condicionaram elevados teores de N-NO3-, representando entre 10,3 e 23,5 % dos teores de N total. O sistema CC reduziu os teores de N total e das frações das substâncias húmicas em 38 e 44 %, respectivamente, na camada superficial do solo. Dentre os sistemas agroflorestais, os sistemas AGP e TR98 causaram redução significativa dos teores de N total, N da matéria orgânica leve (livre e oclusa) e N das substâncias húmicas. O tratamento SILV preservou e, em alguns casos, aumentou os teores de N do solo e, portanto, constituiu um sistema que pode ser recomendado como uma alternativa sustentável de manejo do solo para o semi-árido cearense.

The agroforestry systems have been widely promoted as one sustainable agricultural system, mainly for developing areas, where the external use of resources are not feasible. The aim of this study was to evaluate the impact of one conventional and four agroforestry systems on the contents of total soil nitrogen, mineral nitrogen and different organic nitrogen fractions after five years of experimental cultivation on a Luvisol (Alfisol). The study area was in the semi-arid zone at the National Caprine Research Center (CNPC) of Embrapa, Ceará, Brazil. The following treatments were tested: agrosilvopasture (AGP), silvopasture (SILV), traditional agroforestry in 1998 and 1999 (TR98), traditional agroforestry in 2002 (TR02), conventional cropping (CC), and seasonally dry native vegetation ("Caatinga") (CA). Total-N, N-NH4+, N-NO3-, microbial-N, light organic matter N (free and occluded) and N in the humic substances were evaluated. Results indicated high nitrate-N (NO3-) content in all treatments, accounting for 10.3 to 23.5 % of the total N. The CC treatment reduced the total N and N in humic substances by 38 and 44 %, respectively. The AGP and TR98 agroforestry treatments significantly reduced N in the light organic matter and in humic substances. On the other hand, the SILV system preserved, and in some cases, improved the concentration of the soil. This system can therefore be recommended as a sustainable alternative for soil management in the semi-arid region of Ceará state.

RESUMO Entre os impactos diretos causados pela instalação de redes elétricas sobre a vegetação e o solo ressaltam-se a fragmentação de trechos de mata, os efeitos de borda decorrentes da derrubada de áreas florestadas, o estabelecimento de corredores sob as linhas de transmissão de energia e a aceleração de processos erosivos do solo. Objetivou-se, no presente estudo, propor alternativas de manejo racional da cobertura vegetal de mata atlântica em áreas sob linhas de transmissão de energia elétrica (ALTEEs), instaladas na Serra de Baturité, Ceará. Foram selecionadas e delimitadas ALTEEs situadas na vertente barlavento e nos intervalos altitudinais abaixo de 600, entre 600 e 800 e acima de 800 metros, em redes de média (13,8 kV) e alta tensão (69 kV). Foram selecionadas e avaliadas áreas não-perturbadas, consideradas como referencial no estudo comparativo com as ALTEEs. Os resultados apontaram que o manejo da vegetação em áreas sob linhas de transmissão de energia deve considerar principalmente os seguintes aspectos: (1) o hábito de crescimento das espécies em áreas não-perturbadas; (2) a taxa de crescimento da vegetação; (3) ações distintas nas regiões imediatamente abaixo da rede elétrica, na faixa de servidão e acima da faixa de servidão. A execução do plano de manejo, associado às constantes avaliações técnicas, possibilitarão a adequação da metodologia para as diferentes situações ambientais da Serra de Baturité e/ou outras localidades.

ABSTRACT Forest fragmentation, board effects, establishment of corridors without vegetation and the acceleration of soil erosive processes are some direct impacts occurring on the vegetation and soil due to installation of electrical transmission lines. The goal of the present study was to propose alternatives for the sustainable management of the Atlantic Forest in areas under electrical transmission lines (ALTEEs) installed in the Baturité Mountain, Ceará, Brazil. It was selected and delimited ALTEEs located in the windward slope at the altitudinal ranges below to 600, between 600 and 800 and above to 800 meters in electric networks of low (13,8 kV) and high tension (69 kV). It was also selected undisturbed areas considered as referential in comparison to the ALTEEs. The results pointed out that management of the vegetation in areas under electrical transmission lines should mainly consider the following aspects: (1) growth habit of tree species within undisturbed areas; (2) growth rates of the vegetation; (3) differentiated management procedures on the vegetation situated immediately below the electrical lines, within intervention area and beyond to the intervention area. The execution of the management plan associated to the constant technical evaluations will make possible the adaptation of the methodology for the different environmental situations in the Baturité Mountain and/or other regions.