ABSTRACT The objective of this study was to evaluate substrates formulated with proportions of sewage sludge (SS)-solarized and SS-biochar in the production of seedlings of two indicator crops: lettuce (Lactuca sativa L.) and black wattle (Acacia decurrens Wild). The study was composed of two experiments conducted in greenhouse, in randomized block designs. The treatments consisted of five doses of SS-solarized and SS-biochar, combined with rice husk ash and vermiculite in different proportions (20:40:40, 30:35:35, 40:30:30, 50:25:25 and 60:20:20) and two commercial substrates (controls). Morphophysiological characteristics of the seedlings and the physico-hydric characteristics, pH and electrical conductivity of the substrates were evaluated. The pyrolysis process enhanced the characteristics of SS as a component of substrates, where the substrate with 20% of SS-biochar, 40% of vermiculite and 40% of rice husk ash, presented the better performance.

Resumo Avaliou-se o efeito da retenção de água de substratos para plantas formulados a partir de diferentes proporções de lodo de esgoto (LETE) solarizado, na produção de mudas de acácia-negra (Acacia mearnsii). O experimento foi conduzido em casa de vegetação e no Laboratório de Física do Solo da Embrapa Clima Temperado. O LETE utilizado foi coletado em leitos de secagem de uma Estação de Tratamento de Esgoto aeróbio de Rio Grande - RS. Os tratamentos consistiram de cinco doses de LETE solarizado, combinadas com cinza de casca de arroz e vermiculita em diferentes proporções (20:40:40, 30:35:35, 40:30:30, 50:25:25 e 60:20:20) e dois substratos comerciais (Beifort® S10 B e Mec Plant®). O delineamento experimental foi de blocos casualizados. Foram avaliadas as características físico-hídricas: água facilmente disponível, água tamponante, água remanescente e capacidade de retenção de água. As variáveis de crescimento avaliadas foram: massa fresca da parte aérea e do sistema radicular. O substrato com 20% de LETE solarizado, 40% vermiculita e 40% cinza de casca de arroz apresentou a melhor condição físico-hídrica para o desenvolvimento de mudas de acácia-negra.

Abstract This work evaluated the effect of water retention of plant substrates formulated with different proportions of solarized sewage sludge (SS) in the production of black wattle (Acacia mearnsii) seedlings. The study was conducted in a greenhouse and in the Laboratory of Soil Physics at the Lowland Experimental Station of Embrapa Clima Temperado. The SS was collected in drying beds at an aerobic sewage water treatment plant from Rio Grande, Rio Grande do Sul state. The treatments consisted of five doses of SS-solarized combined with rice husk ash and vermiculite in different proportions (20:40:40, 30:35:35, 40:30:30, 50:25:25 and 60:20:20) and two commercial substrates (controls) (Beifort® S10 B and Mec Plant®). The experimental design was randomized blocks. The following physico-hydric atributes were determined easily available water, buffer water, remaining water and water retention capacity. The following variables were evaluated: dry mass of aerial parts and the dry mass of roots. The substrate with 20% of SS-solarized, 40% of vermiculite and 40% of rice husk ash presented the best physico-hydric condition for the development of black wattle seedlings.

ABSTRACT: Soil physical quality in lowlands from the Pampa biome under no-tillage (NT) plays an important role; therefore, this study aimed to establish a soil physical quality index (SPQi) from a minimum data set to detect the effects of different deployment times of NT in an Albaqualf. The comparison of areas with one (NT1), three (NT3), five (NT5) and seven (NT7) years of notillage was established using as reference a non-cultivated field plot (NC) for at least thirty years, nearby the sites under NT. Soil samples with undisturbed and disturbed structure were collected to determine the physical quality indicators and soil organic matter (SOM) fractions. The factor analysis (FA) was used to identify and select a minimum data set. The SPQi was elaborated by using the deviations of the measured indicators at different deployment times of NT in relation to NC. The SPQi showed sensibility to identify and explain soil physical quality changes with different deployment times of NT. In well-drained lands, higher deployment times of no-tillage promote the physical quality of lowlands.

ABSTRACT: The southern Brazilian lowlands have been historically used for flooded rice cultivation. Over time, heavy machinery and intensive tillage practices have resulted in soil structure disruption, soil compaction, higher production costs and lower agricultural profitability. This study aimed to evaluate the effect of different deployment times of no-tillage (NT). Soil properties including bulk density (BD), compression index (CI), preconsolidation pressure (σp), bulk density at preconsolidation pressure (BDσp), degree of compactness (DC), soil water retention curve (SWRC), plant available water (PAW) and total organic carbon (TOC) content were evaluated using a 30-yr non-cultivated field (NC), adjacent to the experimental plots as a control. The BD, σp, BDσp and DC decreased in response to NT adoption time while the soil water holding capacity increased, allowing for higher PAW. Results from this study demonstrated the positive effects of NT on the overall quality of soils.

ABSTRACT The “Visual Evaluation of Soil Structure” (VESS) is a method used primarily to evaluate the soil structural quality of Oxisols in Brazil and secondly for more specific research, consultancy, and teaching purposes. Since the methodology was never applied and compared with laboratory evaluations of physical properties of hydromorphic soils of the Pampa biome in the south of Brazil, this study evaluated the use of VESS as a visual indicator of the structure quality of a typic eutrophic Albaqualf soil under native grassland, crop-livestock integration, no-tillage, and conventional management systems. Experimental areas with these different management systems were subjected to visual (VESS) and laboratory evaluation of the soil structure. The laboratory evaluation was based on traditional methods and on measurements of bulk density, porosity, aggregate mean weight diameter, aggregate tensile strength (ATS), and total organic carbon (TOC). It was concluded that VESS was efficient in differentiating the management system. The management systems based on minimum soil disturbance and mulching with crop residues improved the soil quality, as evidenced by the VESS scores, bulk density, porosity, aggregation, and organic carbon. The TOC content was inversely related with ATS. The quality of a typic eutrophic Albaqualf was benefitted by organic matter in the surface layer.

Resumo O objetivo deste trabalho foi avaliar os efeitos do sistema plantio direto (PD) e do manejo com preparo convencional (PC) sobre atributos físicos e hídricos de um Planossolo Háplico cultivado com soja, em terras baixas do Sul do Brasil. Amostras indeformadas de solo foram coletadas às camadas de 0,00-0,10, 0,10-0,20 e 0,20-0,40 m, para a determinação dos atributos físico-hídricos, tendo-se monitorado o potencial mátrico do solo com sensores, ao longo de um ciclo de produção da soja. Os valores de macroporosidade foram menores do que 0,10 m3 m-3, independentemente do sistema de manejo do solo, o que restringe a possibilidade de cultivo da soja em sequeiro, pelo comprometimento da difusão de gases. Comparado ao PC, o PD promove a microporosidade na camada de 0,00-0,10 m, o que aumenta o conteúdo de água armazenada no solo e a disponibilidade hídrica para a cultura da soja, com reflexos positivos sobre a produtividade da cultura.

Abstract The objective of this work was to evaluate the effects of no-tillage (NT) and conventional tillage (CT) on the physical and hydric properties of an Albaqualf soil cultivated with soybean, in the lowlands of Southern Brazil. Undisturbed soil samples were collected at the 0.00-0.10, 0.10-0.20, and 0.20-0.40-m soil layers, in order to determine soil physicohydric properties, by monitoring the soil matric potential with sensors, over a cycle of soybean production. Macroporosity values were lower than 0.10 m3 m-3, irrespectively of the soil management system, which restricts the possibility of rainfed soybean cultivation because it affects gas diffusion. In comparison to CT, NT increases microporosity at the 0.00-0.10-m soil layer, which increases soil water content and soil water availability for soybean crop, with positive effects on crop yield.

Resumo O objetivo deste trabalho foi avaliar a qualidade física e as frações da matéria orgânica de um Planossolo sob sistema plantio direto (SPD), com diferentes tempos de implantação, no Sul do Brasil. Amostras de solo foram coletadas nas camadas de 0,00-0,03, 0,03-0,06, 0,06-0,10 e 0,10-0,20 m, tendo-se determinado: a porosidade total (Pt); a macroporosidade (Ma); a microporosidade (Mi); a resistência do solo à penetração (Rp); a densidade (Ds); os macro e microagregados; o diâmetro médio ponderado dos agregados (DMP); o carbono orgânico total (COT); o carbono das frações leve livre (FLL), leve oclusa (FLO) e pesada (FP); os estoques de carbono (EstC), os índices de labilidade (ILC), de estoque (IEC) e de manejo do carbono (IMC). O tempo de implantação SPD aumentou a Pt, a Ma, os EstC, e diminuiu a Mi, a Rp e a Ds. O SPD promove os atributos DMP, ILC, IEC e IMC a partir do quinto ano de implantação, e, portanto, melhora a qualidade física do solo.

Abstract The objective of this work was to evaluate the physical quality and the organic matter fractions of an Alfisol soil under no-tillage (NT) with different deployment times in Southern Brazil. Soil samples were taken at the 0.00-0.03, 0.03-0.06, 0.06-0.10, and 0.10-0.20-m depths, for determining: total porosity (Pt); macroporosity (Ma); microporosity (Mi); soil penetration resistance (Rp); bulk density (Ds); macro- and microaggregates; mean weight diameter (MWD) of soil aggregates; total organic carbon content (TOC); the free light (FLL), light occluded (FLO), and heavy (FP) carbon fractions; carbon stocks (EstC); and the lability (ILC), stock (IEC), and carbon management (IMC) indexes. SPD deployment time increased Pt, Ma, and EstC, and decreased Mi, RP, Ds. NT promotes MWD, ILC, IEC, and IMC after five years of deployment, and, therefore, it improves soil physical quality.

A sustentabilidade do arroz (Oryza sativa L.) irrigado em solos de várzea está alicerçada na utilização da rotação e sucessão de culturas, fundamentais para o controle do arroz-vermelho e preto. Os reflexos sobre os atributos dos solos de várzea merecem estudos em especial sobre a compactação do solo. O objetivo deste trabalho foi identificar camadas compactadas em Planossolo submetido a diferentes sistemas de cultivo e preparo, avaliando-se a densidade do solo (Ds) pela Tomografia Computadorizada de Raios Gama (TC). A análise foi realizada em um experimento de longa duração, conduzido de 1985 a 2004, na Estação Experimental da Embrapa Clima Temperado, Capão do Leão, RS, num delineamento experimental em blocos ao acaso, com sete tratamentos, cada um com quatro repetições (T1 - um ano de arroz com preparo convencional do solo seguido de dois anos de pousio; T2 - cultivo contínuo de arroz com preparo convencional do solo; T4 - rotação de arroz e soja (Glycine max L.) com preparo convencional do solo; T5 - rotação de arroz, soja e milho (Zea maiz L.) em preparo convencional do solo; T6 - plantio direto de arroz no verão em sucessão do azevém (Lolium multiflorum L.) no inverno; T7 - rotação de arroz sob plantio direto e soja sob preparo convencional do solo; T8 - testemunha: solo sem cultivo). A Tomografia Computadorizada de Raios Gama permitiu detectar que o plantio direto de arroz no verão em sucessão do azevém no inverno não resultou na formação de camadas compactadas; a utilização de dois anos de pousio, no sistema de produção de arroz irrigado, não foi suficiente para evitar a formação de uma camada superficial compactada; e a rotação de arroz, soja e milho com preparo convencional do solo apresentou duas camadas compactadas (0,0 a 1,5 cm e 11 a 14 cm), indicando que essas podem limitar a produção agrícola nesse sistema de produção em Planossolos.

The sustainability of irrigated rice (Oryza sativa L.) in lowland soils is based on the use of crop rotation and succession, which are essential for the control of red and black rice. The effects on the soil properties deserve studies, particularly on soil compaction. The objective of this study was to identify compacted layers in an Albaqualf under different cultivation and tillage systems, by evaluating the soil bulk density (Ds) with Gamma Ray Computed Tomography (TC). The analysis was carried out in a long-term experiment, from 1985 to 2004, at an experimental station of Embrapa Clima Temperado, Capão do Leão, RS, Brazil, in a random block design with seven treatments, with four replications (T1 - one year rice with conventional tillage followed by two years fallow; T2 - continuous rice under conventional tillage; T4 - rice and soybean (Glycine Max L.) rotation under conventional tillage; T5 - rice, soybean and corn (Zea maize L.) rotation under conventional tillage; T6 - rice under no-tillage in the summer in succession to rye-grass (Lolium multiflorum L.) in the winter; T7 - rice under no-tillage and soybean under conventional tillage rotation; T8 - control: uncultivated soil). The Gamma Ray Computed Tomography method did not identify compacted soil layers under no-tillage rice in succession to rye-grass; two fallow years in the irrigated rice production system did not prevent the formation of a compacted layer at the soil surface; and in the rice, soybean and corn rotation under conventional tillage two compacted layers were identified (0.0 to 1.5 cm and 11 to 14 cm), indicating that they may restrict the agricultural production in this cultivation system on Albaqualf soils.