resumo o conhecimento sobre as alterações físicas e qualidade do solo é importante para o direcionamento adequado das estratégias de manejo a serem utilizadas quando da exploração do solo por cultivos agrícolas. este trabalho teve como objetivo avaliar os efeitos do cultivo e da aplicação de um biofertilizante, obtido a partir de esterco bovino, sobre a qualidade física de um cambissolo cultivado com Ficus carica l., irrigado por sistema de gotejamento. Para fins de avaliação da qualidade física, foram contempladas cinco situações de solo: sob cultivo de figo sem aplicação do biofertilizante (testemunha); com aplicação de 20, 40 e 60 % do biofertilizante na lâmina de irrigação; e mata nativa secundária (testemunha adicional), até a profundidade de 0,3 m, nas camadas de 0,0-0,1, 0,1-0,2; e 0,2-0,3 m, com quatro repetições. nessas camadas, foram coletadas amostras de solo com estrutura deformada e indeformada para realizar análises físicas, como granulometria, argila dispersa em água, carbono orgânico, densidade das partículas e do solo, resistência do solo à penetração e curva característica de água no solo. o cultivo do solo nas condições descritas nesta pesquisa, como preparo do solo por aração e gradagem, uso de irrigação e todos os tratos culturais necessários à condução da cultura de figo, não piora a qualidade física do solo em nenhuma das camadas avaliadas. A aplicação de biofertilizante melhora a qualidade física do solo, particularmente no tocante à retenção de água em decorrência do aumento da microporosidade.Palavras-chave: degradação física do solo, matéria orgânica, cultura do figo.Recebido para publicação em 18 de julho de 2014 e aprovado em 13 de fevereiro de 2015.

Biochar is a solid material formed during biomass thermochemical decomposition processes. This organic compound has particular properties that may cause effects on soils depending on its feedstock and processing conditions. Thus, the characteristics and purpose of use of this material must be recognized prior to its use. Two types of biochar, derived from different wood sources, were compared, one from caatinga biome species and another from cashew trees. Two species from caatinga biome were used, jurema-preta (Mimosa tenuiflora Willd. Poir.), and marmeleiro (Croton sonderianus Müll. Arg.). This study aimed to identify the best biochar material regionally available to increase water-holding capacity in the soil, based on laboratory tests and microstructural porosity evaluation. Biochar from Caatinga wood demonstrated an improved water-holding capacity if compared to cashew wood biochar. The particle diameters of 2 and 4 mm showed the highest levels, which were 2,268 g.g-1 for caatinga wood and 0.574 g.g-1 for cashew wood biochars, respectively. While the smaller quantities of macropores and a larger number of micropores (smaller radius) could explain the higher water-holding capacity for biochar from caatinga wood, the thick lignified cell walls of biochar from cashew wood support the idea of a hydrophobic effect contributing to water lower holding capacity.

Forest management activities influence fine root development, total soil carbon (TSC) and size of aggregates. A field experiment was carried out in Vertisols of two adjacent catchments in a seasonally dry tropical forest (SDTF) to investigate the thinning on fine-root biomass, stock of the total soil carbon and aggregate size. The catchments are located in the State of Ceará, Brazil. The control catchment of 2.1 ha has been under regenerating vegetation for 35 years (RC35), while the second catchment (1.1 ha) was subjected to thinning (TC5) in December of 2008. The analysed variables were: fine-root biomass in the 0-10, 10-20 and 20-30 cm soil layers, TSC and mean weight diameter of the soil aggregates in the 0-20, 20-40 e 40-60 cm layers. The data were submitted to Pearson correlation analysis and compared by paired t-test (P < 0.05). The 0-10 cm layer of the TC5 management stored double the average amount of fine-roots found in the RC35. Under the TC5 management, stocks of soil TSC increased by 237 and 151% in the 20-40 and 40-60 cm layers, respectively, when compared with RC35. Aggregates 2.15 times greater than those found under RC35 management were obtained in the topsoil (0-20 cm) under the TC5 management. The implementation of thinning in a Vertisol of a SDTF emerges as an alternative management to be considered in projects for sustainability in the semi-arid region, contributing to an improvement in soil structure as well as an increase in the stocks of total carbon.

-Soil-water characteristic curve (SWCC) is an important tool for water management in irrigated agriculture. However, factors such as texture and structure of soils influence SWCC behavior. According to the literature, wetting and drying cycles alter SWCC. A similar process of re-saturation and drying occurs during SWCC obtainment under laboratory conditions. Based on the hypothesis that re-saturation process alters SWCC due to clay loss in the sample, this study aimed to obtain the SWCC, S index, and pore size distribution from samples submitted to re-saturation cycles, as well as from not re-saturated samples but under higher matric potentials (−2, −4, −6, −8, and −10 kPa). For this, disturbed and undisturbed soil samples, collected from the A (sandy texture) and Btg (sandy clay loam texture) horizons of a Argissolo Acizentado, were used. After obtaining SWCC, each air-dried soil sample was submitted to particle size and clay dispersed in water analyses to verify whether the soil lost clay. The experimental design was a completely randomized design with two methods of SWCC constructing (with and without re-saturation) and eight replications. The re-saturation process generates a loss of clay in the sample, not causing significant changes in SWCC considering the assessed textural soil classes. In addition, sandy soil samples are more sensitive to changes in pore size distribution when submitted to re-saturation.Keywords: Irrigation management. Soil porosity. Water in soil.EFEITO DA RESSATURAÇÃO DA AMOSTRA SOBRE A CURVA CARACTERÍSTICA DE ÁGUA NO SOLO RESUMO -A curva característica de água no solo (CCAS) constitui importante ferramenta no manejo da água na agricultura irrigada. Entretanto, vale ressaltar que fatores como textura e estrutura do solo influenciam seu comportamento. Há informações na literatura que ciclos de umedecimento e secagem alteram a CCAS. Saliente-se que processo similar, de ressaturação e secagem, ocorre durante a obtenção da CCAS em laboratório. Tendo como hipótese que o processo de ressaturação, por provocar perda de argila na amostra, altera a CCAS, objetivou-se obter a CCAS, o índice S e a distribuição dos poros por tamanho a partir de amostras submetidas a ciclos de ressaturação em oposição àquelas não sujeitas a este processo em maiores potenciais mátricos (−2, −4, −6, −8 e −10 kPa). Para tanto, utilizaram-se amostras com estrutura deformada e indeformada, coletadas do horizonte A (textura arenosa) e Btg (textura franco argilo-arenosa) de um Argissolo Acinzentado. Após a obtenção da CCAS, cada amostra foi levada à condição de terra fina seca ao ar e submetida à análise granulométrica e de argila dispersa em água para verificar se houve perda de argila. O delineamento estatístico foi o inteiramente casualizado, com dois métodos de construção da CCAS -com e sem ressaturação -e oito repetições. Concluiu-se que o processo de ressaturação gera perda de argila na amostra, mas não provoca alterações significativas na CCAS nas classes texturais avaliadas; e que as amostras de solo de t...

DESEMPENHO DE SISTEMAS DE LEITURA DE TENSIÔMETRO EM CONDIÇÕES DE TEMPERATURA CONTROLADA  JOSIMAR DE AZEVEDO1; ALCIONE GUIMARÃES FREIRE1; THIAGO LEITE DE ALENCAR1; CARLOS LEVI ANASTÁCIO DOS SANTOS1; RAIMUNDO NONATO DE ASSIS JÚNIOR1; FRANCISCO MARCUS LIMA BEZERRA2 E JAEDSON CLÁUDIO ANUNCIATO MOTA1 *Artigo extraído da dissertação do primeiro autor.1Departamento de Ciências do Solo, Universidade Federal do Ceará, UFC, Av. Mister Hull, 2977, 60.021-970, Fortaleza, CE, Brasil. E-mail: eng.azevedofmi@hotmail.com; alcionegf@hotmail.com; thiagoleitealencar@yahoo.com.br; carloslevi@hotmail.com; assisjr@ufc.br; jaedson.mota@ufc.br.2Departamento de Engenharia Agrícola, Universidade Federal do Ceará, UFC, Av. Mister Hull, 2977, 60.021-970, Fortaleza, CE, Brasil. E-mail: mbezerra@ufc.br.  1 RESUMO Objetivou-se aferir sistemas alternativos ao vacuômetro de mercúrio para a quantificação do potencial mátrico da água no solo, definir o tempo para reestabelecer o equilíbrio entre as tensões da água no interior do tensiômetro e no solo após a inserção da agulha do tensímetro no tensiômetro, e quantificar erros na determinação do potencial mátrico e da umidade a partir dos sistemas alternativos. O ensaio foi realizado em vasos, em laboratório, com três tensiômetros por vaso, seis repetições, nas profundidades de 0,20, 0,35 e 0,50 m. Definido o tempo de equilíbrio comparou-se o potencial mátrico e a umidade volumétrica nos três sistemas de leitura. Concluiu-se que a leitura do tensímetro pode ser realizada em quaisquer dos tempos desde 30 a 180 segundos; o tensímetro substitui o vacuômetro de mercúrio desde a saturação até a capacidade de campo, e o vacuômetro de Bourdon da condição na ou próxima à capacidade de campo até a situação mais seca; e os erros decorrentes dos sistemas alternativos se refletiram na estimativa da umidade do solo, com subestimativa dos valores a partir da capacidade de campo. Palavras-chave: Potencial mátrico, água no solo, irrigação.  AZEVEDO, J.; FREIRE, A. G.; ALENCAR, T. L.; SANTOS, C. L. A.; ASSIS JÚNIOR, R. N.; BEZERRA, F. M. L.; MOTA, J. C. A.PERFORMANCE OF TENSIOMETER READING SYSTEMS UNDER CONTROLLED TEMPERATURE CONDITIONS  2 ABSTRACT                                      The study aimed at assessing alternative systems to the mercury vacuum for quantification of water matric potential, to define the time for restoring the equilibrium between the water tension in the interior of the tensiometer, and in the soil after the insertion of the needle in the tensiometer, and to quantify errors in the determination of the water matric potential and the soil moisture from the alternative systems. The essay was carried out in pots in the laboratory. Three tensiometers were installed per pot, six replications, at depths of 0.20, 0.35 and 0.50 m. After the definition of the equilibration time, the matric potential and volumetric moisture were compared in the three systems. It was concluded that after the insertion of the needle of the tensiometer the reading can be performed in any of the times from 30 to 180 seconds; The tensiometer replaces the mercury vacuum gauge from saturation to field capacity and the Bourdon vacuum gauge from the condition at or near the field capacity to the driest condition; and the errors resulting from alternative systems were reflected in the estimation of the soil moisture whereas the alternative systems underestimated the values from the field capacity. Keywords: Matric potential, soil water, irrigation.

Rain-fed agriculture in the semi-arid northeast of Brazil faces stronger challenges regarding water for agriculture. Biochar is recognized to promote soil water holding capacity. Its properties vary widely with feedstock material and processing conditions, so it is recognized the importance of its characterization and performance evaluation, before use. The objective of this study was to identify best regional available biochar for soil water-holding capacity increase, based on laboratory tests and microstructural porosity evaluation. Types of biochar were compared, according to wood source. Cashew tree and two species from caatinga biome were used, jurema-preta (Mimosa tenuiflora (Willd.) Poir. and marmeleiro (Croton sonderianus Müll. Arg.). For water holding evaluations, both biochar were submitted to Hainnes Funel. Samples were crushed and brought to the laboratory and separated using sieves of 16 mm; 8 mm; 4 mm; 2 mm; 1 mm; 0.5 mm; 0.25 mm; 0.12 mm and <0.12 mm mesh. Samples with particle size diameters of 2 mm and 4mm were submitted to Hainnes Funel. Transversal sections of both biochars were prepared to be observed under a scanning electron microscope, identifying macropores and micropores. Caatinga wood biochar demonstrated greater water holding capacity than cashew wood one in all evaluated diameters. Greater levels are observed related to caatinga wood biochar, 1.89 g g-1 for to particle size diameter of 2 mm and 2,27 g g-1 for 4mm and cashew wood biochar demonstrated water holding capacity of 0.57 and 0.53 g g-1 to 2mm and 4 mm particle size diameters respectively. The fewer quantity of macropores and larger number of micropores may give caatinga wood biochar higher water holding capacity, while thickly lignified cell walls of cashew wood biochar supports the idea that a hydrophobic effect may contribute to its lower holding capacity.