ABSTRACT Soil Education aims to give individuals a transforming formative process for conscious actions related to the soil in their life experiences in and with the world. As such, the educational methodologies addressing soil-related contents should be in dialogue with the purpose of this educational process. On the perspective of education for social transformation, it is recommended that professors of Higher Education avoid from pedagogical actions with traditional approaches, and start using other strategies and methodologies centered on students and their context. With the challenge of addressing the implementation of emancipatory principles in educational procedures within the disciplinary structure of a traditional paradigm of education and achieving the aim of Soil Education, we put forward the Alternative Methodology of Problem Cases (AMPC), which was shaped up from two methodologies with constructivist principles, P roblem-Based Learning (PBL) and Team-Based Learning (TBL). This methodology is divided into three phases (preparation, application, and reflection), which are in turn divided into seven steps that complement each other (recovery of socio-historical knowing and knowledge; study of the themes; problem case resolution; team guidance; individual activity report; and individual and collective feedback). In addition, the steps contain individual and team assignments, which revolve around the resolution of problem cases related to the future profession. The AMPC is different from PBL and TBL as the former is grounded on emancipatory principles that facilitate the development of educational processes that value the socio-historical knowing and knowledge of individuals and enable the development of students’ autonomy, creativity, critical thinking, and awareness for actions in real life. The challenges through which individuals can develop relational, complex, and critical thinking, apply them to professional life situations, confront and reframe their knowledge and knowing, as well as create solutions and plan future scenarios with the practice of solving problem cases about soils consist in the capacity of AMPC to be efficient to soil learning.

ABSTRACT The teacher’s formative process is developed by a critical reflective response to the paths of life, the profession, and its practices. The teacher’s formative process analysis should consider the process’s objectives (theoretical, practical, and emancipatory), and the dimensions that make up the teacher (person, practices, and profession). As a result, this study aims to introduce the elements that outline the categories stemming from the relationship matrix between the objectives and the dimensions, and use them to analyze a formative process in Soil Education assessed using Formative (Auto)biographical Narratives. The research subjects were 61 teachers active in the Public Education System in the cities of Campo Largo and Curitiba, state of Paraná, Brazil, who took part in the formative process known as Soil Program for Teachers within the Soil at School Project from the Federal University of Paraná, held in 2018. Data collection was performed through written narratives given in response to three groups of open-ended questions, which aimed to encourage teachers to think deep. We performed the Content Analysis in the narratives while differentiating expressions associated with the elements in each category, and, consequently, the frequency of the expressions was recorded. As for the Theoretical Objectives within the analysis of the Program, in which the teacher is the study object, we found that the teachers built and rebuilt knowledge and expertise about the soil while drawing on the relationship between the formative conceptual approaches and the recollection of their professional and personal experiences through the Narratives. Within the Practical Objectives, in which self-formation is analyzed, the Narrative influenced a critical and reflective perspective about the person, the practice, and the profession, while driving teachers to their self-formation and creating their professional identity. As for the analysis of the Emancipatory Objectives, which demonstrate the change of reality, the teacher’s transformation was seen in their change of attitude and practices, as well as in their intent to get involved with the school. We concluded that the elements proposed to outline the nine categories were effective to analyze the formative process in Soil Education, by taking into account, in an integral way, the Objectives of the analysis and the Dimensions that make up the teacher while in his/her formative process. We would also like to point out that the Narratives were an important instrument for continuous education in Soil Education.

ABSTRACT: Soil Fertility is one of the most relevant fields of Soil Science related to agricultural production, especially in tropical and subtropical environments, due to the prevalence of weathered and naturally unproductive soils. However, indicators of Soil Fertility currently used do not represent what actual happens in the soil; once must be understood as a process. The wisdom of this importance occurred in Antiquity and evolved until the mid-19th century, when the mineralist concept was proposed, which is still dominant in Brazil and worldwide. In this process, Soil Fertility has been associated with current perceptions, soil chemical properties and management systems in the development of agriculture over time. During the evolution of Brazilian agriculture, from the 1960’s onwards and most notable with the consolidation of conservation management in the 1990’s, Intrinsic limitations were increasingly evident on the ability of indicators to assess the actual level of Soil Fertility and the respective response of the plants. Concurrently, the view of the soil as an open system was strengthened, and the conception of fertility began to constitute a property that emerges from the functioning of the soil, whose processes are self-organizing, due to the continuous flows of energy and matter driven by organic compounds. In this context, we present a part of the history of Brazilian agriculture, relating it to its management and Intrinsic limitations of indicators to assess Soil Fertility due to changes in soil functioning. The Intrinsic limitations added to understanding based on a systemic approach of the functional processes of the soil are the practical and theoretical bases for the proposition of another concept: Systemic Soil Fertility .

Resumo A pressão humana sobre os serviços ecossistêmicos tem resultado em impactos indesejáveis sobre o bem-estar humano. Com o Projeto Millennium, várias pesquisas interdisciplinares têm sido desenvolvidas em todo o mundo com o objetivo de entender esses impactos sobre os fluxos e os processos dos ecossistemas e internalizar os custos e os benefícios dos serviços ecossistêmicos para a produção. O solo fornece muitos serviços ecossistêmicos, uma vez que sua multifuncionalidade é a base para a produção de alimentos, filtração de água, ciclagem de nutrientes e outros bens essenciais à vida. Este artigo apresenta os principais conceitos e classificações dos serviços ecossistêmicos do solo e de suas funções; os indicadores e os métodos de avaliação, modelagem e valoração dos serviços ecossistêmicos; algumas aplicações recentes para avaliar impactos de práticas de manejo agrícola sobre os serviços ecossistêmicos do solo; bem como os desafios e as oportunidades para a pesquisa e para o desenvolvimento de políticas públicas relacionadas à sustentabilidade agroambiental no Brasil. Apesar de o papel do solo para prestação de serviços ecossistêmicos ainda ser subestimado, os cientistas têm gradualmente reconhecido os processos e as funções do solo como fundamentais para avaliar os serviços ecossistêmicos e os efeitos do uso e manejo da terra sobre eles. Abordagens interdisciplinares que integrem ciência e políticas públicas são necessárias para construir uma governança com base em serviços ecossistêmicos.

Abstract Human pressure on ecosystems has undesirable impacts on human well-being. After the Millennium Project, much interdisciplinary research has been developed worldwide aiming to understand these impacts on ecosystem flows and processes, and to learn about the costs and the benefits of ecosystem services for production. Soil provides many ecosystem services, since its multi-functionality is the basis for food production, water filtration, nutrient cycling, and other goods essential to life. This article presents the main concepts and classifications of soil ecosystem services and of its functions; the indicators and the methods for assessment, modeling, and valuation of ecosystem services; some recent applications to assess and evaluate impacts of agricultural management practices on soil ecosystem services; as well as challenges and opportunities for research and for development of public policies related to agro-environmental sustainability in Brazil. Although the role of soil in supplying ecosystem services is yet undervalued, scientists are gradually recognizing soil processes and functions as fundamental to assess ecosystem services and the effects of land use and management on them. Interdisciplinary approaches to integrate science and public policies are necessary to build governance based on ecosystem services.

A qualidade do solo em plantio direto está relacionada ao sistema de culturas e pode ser avaliada pelo teor de matéria orgânica particulada (>53 ∝m), em razão da funcionalidade que essa fração proporciona ao solo e à sua sensibilidade às diferenças de manejo. Visando estudar a qualidade do solo em sistemas de culturas em plantio direto, este trabalho foi conduzido em experimento de longa duração (21 anos) em Latossolo Vermelho distrófico típico nos Campos Gerais do Paraná. Seis sistemas de culturas foram avaliados, em que trigo-TR (Triticum aestivum L.), soja-SO (Glycine max L.), milho-MI (Zea mays L.), aveia-preta-AV, para cobertura (Avena strigosa Schreb.), ervilhaca-ER, para cobertura (Vicia villosa Roth); azevém-AZ, para feno (Lolium multiflorum Lam.); ou alfafa-AL, para feno (Medicago sativa L.) compuseram os seguintes sistemas: TR-SO (referência), ER-MI-AV-SO-TR-SO, ER-MI-TR-SO, AV-MI-TR-SO, AZ-MI-AZ-SO e AL-MI (milho a cada três anos). Os estoques de carbono orgânico total (COT), nitrogênio total (NT) e de C e N na matéria orgânica (MO) particulada (>53 µm) e associada aos minerais (<53 µm) foram determinados em 0-5, 5-10 e 10-20 cm. O sistema semiperene AL-MI apresentou os maiores estoques de COT e NT na camada de 0-20 cm (63,6 Mg ha-1 COT e 4,6 Mg ha-1 NT), com incrementos anuais de 0,23 Mg ha-1 COT e 0,03 Mg ha-1 NT, em relação ao sistema TR-SO. O sistema AL-MI também teve os maiores estoques de C e N na MO particulada nessa camada (12,5 e 0,91 Mg ha-1, respectivamente), por causa da maior adição de fitomassa pelas raízes e a proteção física dos resíduos orgânicos. Os menores estoques de COT e NT na camada 0-20 cm ocorreram no sistema ER-MI-TR-SO (57,8 Mg ha-1 COT e 4,03 Mg ha-1 NT), sem apresentar incremento anual em relação ao sistema TR-SO. Os estoques de C e N na MO particulada foram de 10,4 e 0,67 Mg ha-1, respectivamente. Essa tendência repetiu-se para as camadas individuais, com diferença significativa entre os sistemas na camada de 0-5 cm e não significativa, para as de 5-10 e 10-20 cm. Na média dos sistemas, a MO particulada contribuiu em torno de 30 % para o estoque total de C na camada 0-5 cm. Rotação de culturas com espécies que tenham sistema radicular ativo por mais tempo, como o sistema semiperene AL-MI, tem potencial de incrementar o estoque total de C e N, especialmente da fração MO particulada, proporcionando funcionalidade ao solo e, consequentemente, qualidade.

Soil quality in no-till systems is related to the crop systems and may be evaluated through particulate organic matter (>53 ∝m) stock due to the functionality this property provides to the soil and its sensitivity to management practices. Aiming to assess soil quality no-till crop systems, this study was carried out through a long-term experiment (21 years) in a Latossolo Vermelho distrófico típico (typical Oxisol) in Ponta Grossa, PR, Brazil. Six crop systems were assessed. Wheat-TR (Triticum aestivum L.), soybean-SO (Glycine max L.), corn-MI (Zea mays L.), oat-AV (Avena strigosa Schreb.) as a cover crop, vetch-ER (Vicia villosa Roth) as a cover crop, ryegrass-AZ (Lolium multiflorum Lam) for hay, or alfalfa-AL (Medicago sativa L.) for hay comprised the following systems: TR-SO (reference), ER-MI-AV-SO-TR-SO, ER-MI-TR-SO, AV-MI-TR-SO, AZ-MI-AZ-SO and AL-MI (corn every three years). The stocks of total organic carbon (COT) and total N (NT) and C and N in particulate (>53 ∝m) and mineral-associated organic matter (<53 ∝m) were determined at 0-5, 5-10 and 10-20 cm. The semiperennial AL-MI system had the greatest COT and NT stocks in the 0-20 cm layer (63.6 Mg ha-1 COT and 4.6 Mg ha-1 NT), and increased annual sequestration rates in relation to the TR-SO baseline system (0.23 Mg ha-1 year-1 COT and 0.03 Mg ha-1 year-1 NT). The AL-MI system also had the highest C and N stocks in the particulate organic matter in the same layer (12.5 and 0.91 Mg ha-1, respectively) due to its higher C addition from root plant matter and the physical protection of organic crop litter. The ER-MI-TR-SO system had the lowest C and N stocks in the 0-20 cm layer with values of totals stocks of 57.8 and 4.03 Mg ha-1, respectively, and without an increased annual sequestration rate because the stocks were similar to the TR-SO baseline system; C and N stocks in particulate organic matter were 10.4 and 0.67 Mg ha-1, respectively. This tendency was repeated for individual layers with a significant difference between systems in the 0-5 cm layer and no significant difference in the 5-10 and 10-20 cm layers. The particulate organic matter contributed around 30 % to total C stocks in the 0-5 cm layer on average in the systems. Crop rotations with species that have active root systems for a longer time, such as the semi-perennial AL-MI system, could increase total C and N stocks, especially the particulate organic matter, which promote soil functionality and, consequently, greater soil quality.

O plantio direto de qualidade depende de um manejo adequado do solo que promova melhorias em sua estrutura. Isso está associado ao sistema de culturas adotado. O objetivo deste trabalho foi avaliar a contribuição de sistemas de culturas de longo prazo (18 anos) na qualidade estrutural de um Latossolo Vermelho mesoférrico argiloso sob plantio direto nos Campos Gerais do Paraná. Foram avaliados cinco sistemas de culturas: trigo-soja [Tr-So]; aveia-milho-trigo-soja [Av-Mi-Tr-So]; ervilhaca-milho-trigo-soja [Er-Mi-Tr-So]; azevém-milho-azevém-soja [Az-Mi-Az-So]; e alfafa-milho [Alf-Mi]. Amostras de solo foram coletadas nas camadas de 0-5, 5-10 e 10-20 cm, em anéis volumétricos e em blocos com estrutura preservada. Na camada de 0-5 cm, as menores densidades de solo tenderam a ocorrer nos sistemas Av-Mi-Tr-So (0,96 Mg m-3) e Er-Mi-Tr-So (0,93 Mg m-3). Nas camadas de 5-10 e 10-20 cm, as menores densidades de solo ocorreram no sistema Alf-Mi (1,14 e 1,17 Mg m-3, respectivamente). Tendência coerente foi observada para a macroporosidade, que na camada superficial foi maior nos sistemas Av-Mi-Tr-So (0,29 m³ m-3) e Er-Mi-Tr-So (0,30 m³ m-3) e, nas camadas de 5-10 e 10-20 cm, tendeu a ser maior no sistema Alf-Mi (0,19 m³ m-3). A microporosidade não apresentou tendência clara entre os sistemas. A condutividade hidráulica saturada teve relação direta com a macroporosidade, com Er-Mi-Tr-So apresentando o maior valor na camada de 0-5 cm (224 mm h-1) e Alf-Mi nas camadas de 5-10 (170 mm h-1) e 10-20 cm (147 mm h-1). O sistema Er-Mi-Tr-So apresentou o menor diâmetro médio ponderado úmido de agregados na camada de 0-5 cm (2,39 mm), e o Tr-So, o maior (3,04 mm). Os maiores valores de resistência mecânica do solo à penetração foram observados no sistema Tr-So, superando 1,5 MPa na camada de 7,5 a 22,5 cm de profundidade. O sistema Alf-Mi apresentou o menor grau de compactação (0,2 MPa cm). Os resultados são atribuídos, principalmente, à ação das raízes das espécies que constituem os sistemas de culturas e à intensidade de tráfego de máquinas em cada sistema. Considerando a camada de 0-20 cm como um todo, o sistema semiperene Alf-Mi possui maior capacidade de promover melhorias na qualidade estrutural do solo, em comparação aos sistemas baseados em cultivos de espécies anuais. Sistemas bianuais de rotação, baseados em plantas de cobertura como aveia-preta ou ervilhaca, promovem melhorias na qualidade estrutural do solo em relação à sucessão trigo-soja.

The quality of no-tillage systems depends on an adequate soil management that promotes soil structure improvements. This is associated to the cropping system adopted. This study investigated the effect of long-term no-tillage systems (18 years) on the structural quality of a sandy-clay to clay Oxisol (Latossolo Vermelho) in the region of Campos Gerais, Paraná, Brazil. Five cropping systems were assessed: wheat-soybean [Wt-So], black oat-maize-wheat-soybean [Ot-Mz-Wt-So], vetch-maize-wheat-soybean [Vt-Mz-Wt-So], ryegrass-maize-ryegrass-soybean [Rg-Mz-Rg-So]; and alfalfa-maize [Alf-Mz]. Soil was sampled from the layers 0-5, 5-10 and 10-20 cm, in cylinders and in blocks with undisturbed structure. In the 0-5 cm layer, bulk density was lowest in the Ot-Mz-Wt-So (0.96 Mg m-3) and Vt-Mz-Wt-So systems (0.93 Mg m-3). In the 5-10 and 10-20 cm layers, the bulk density tended to be lowest in Alf-Mz systems (1.14 and 1.17 Mg m-3, respectively). A similar trend was observed for macroporosity, which in the top layer was greater in Ot-Mz-Wt-So (0.29 m³ m-3) and Vt-Mz-Wt-So (0.30 m³ m-3) and in the 5-10 and 10-20 cm layers tended to be greater in the Alf-Mz system (0.19 m³ m-3). No clear trend was observed for microporosity. The saturated hydraulic conductivity was directly related with macroporosity, and was highest for Vt-Mz-Wt-So in the 0-5 cm layer (224 mm h-1) and Alf-Mz in the layers 5-10 (170 mm h-1) and 10-20 cm (147 mm h-1). In the Vt-Mz-Wt-So system, the mean weight diameter of aggregates was lowest in the 0-5 cm layer (2.39 mm) and highest (3.04 mm) in the Wt-So. The highest cone index values were observed in the Wt-So system, with over 1.5 MPa in the 7.5-22.5 cm layer. The compaction degree was lowest in the Alf-Mz system (0.2 MPa cm). Results were attributed mainly to the role of the crop roots of the systems and to the intensity of machinery traffic. Considering the 0-20 cm layer as a whole, the capacity to promote soil structural quality improvements was greater for the semi-perennial Alf-Mz system than for systems based on annual species. Bi-annual rotation systems, based on cover crops such as black oat and vetch, promote soil structural quality improvements compared to the wheat - soybean succession.

Phosphorous application effects were evaluated on ryegrass dry matter (DM) accumulation, root development and plant tissue concentration of phosphorus, nitrogen and carbon aiming to determinate the nutritional status of the pasture, as well as to verify the possibility to establish a phosphorus dilution curve for this pasture. Also, the development of phosphorus and ryegrass cultivated with the residual effect of phosphorus fertilization was determined. The experiment was carried out in Pinhais County - Paraná State on a Cambisol with very low phosphorus levels. The experiment was of random blocks design and treatments consisted of five phosphorus rates of triple superphosphate (0, 45, 90, 180 and 360 kg P2O5 ha-1) applied to soil surface with four replications. Phosphorus fertilization promoted linear increments in the soil phosphorus availability and resulted, in the first year, in early pasture production and higher phosphorus content in the plant. Nitrogen and carbon contents were not affected. Phosphorous application increased ryegrass DM accumulation in all periods, ranging from 16 to 2826 kg DM ha-1 at flowering stage, for zero and 360 kg P2O5 ha-1, respectively. Root density was positively influenced by phosphorus supply, and the rate of 45 kg P2O5 ha-1 was effective for maximum root development. The residual effect of phosphorus fertilizer provided enhancement of yield and phosphorus plant concentration for both sorghum and ryegrass in the second year.

A utilização de dejetos de animais na produção agrícola é uma alternativa de disposição do resíduo gerado na atividade pecuária, porém se aplicado inadequadamente pode causar problemas ambientais. Nesse sentido, o objetivo geral deste trabalho foi avaliar as concentrações e perdas de C e N por escoamento superficial em quatro doses de dejeto líquido bovino (0, 60, 120, 180 m³ ha-1 ano-1) aplicado em Latossolo franco-argiloarenoso com 13 % de declividade, manejado em plantio direto com soja, aveia-preta, milho e trigo, em sistema de rotação. O escoamento superficial foi coletado durante dois anos e sete meses em galões de 60 L após cada chuva, com geração de escoamento em pelo menos uma parcela. Os nutrientes solúveis foram determinados em amostra filtrada por uma membrana de éster de 0,45 µm e os nutrientes totais, em amostras não filtradas. A aplicação de dejeto líquido bovino reduziu as perdas de C orgânico e N por escoamento superficial, com consequências positivas para a qualidade da água em corpos hídricos a jusante. Porém, doses crescentes de dejeto tendem a aumentar a concentração dos referidos elementos e, por conseguinte, diminuir a qualidade da água. As concentrações médias ponderadas de nitrato estiveram abaixo do limite permitido pela legislação brasileira, porém as de amônio ficaram acima do máximo permitido, indicando a necessidade de práticas de controle e retenção do escoamento superficial, a fim de evitar a entrada do nitrato nos corpos d'água, mesmo em áreas sob plantio direto. Cabe ressaltar que esses dados foram obtidos em condição de baixo potencial poluidor, ou seja, relevo com 13 % de declividade, baixa precipitação e intervalo mínimo de dez dias entre a aplicação do dejeto e a ocorrência de chuva, com formação de escoamento superficial. Além disso, há a necessidade de estudos futuros para avaliar a lixiviação de nitrato.

The use of manure in agricultural system is a possibility to dispose of the waste generated in animal production, but improper use can cause environmental problems. The general objective of this study was to evaluate carbon and nitrogen concentrations and losses in runoff in four doses of liquid dairy manure (0, 60, 120, 180 m³ ha-1 yr-1) applied to a silt clay loam Oxisol with 13 % slope, in no-till with soybean, oat, corn, and wheat in crop rotation. The runoff was collected for two years and seven months in 60 L containers after every rain with runoff from at least one plot. Soluble nutrients were analyzed in runoff samples filtered through a 0.45 µ m membrane and total nutrients in unfiltered samples. The application of liquid dairy manure reduced the losses of organic carbon and nitrogen, with positive consequences for water quality. However, higher rates tended to increase the concentrations of these elements and, consequently, reduce water quality. The weighted average concentrations of nitrate were below the limit allowed by Brazilian legislation, but ammonium exceeded the threshold values, indicating the need of control measures to prevent the runoff from reaching the water bodies, even in no-tillage systems. It should be pointed out that these data were obtained under low potential polluting conditions, i.e, on 13 % slope, low rainfall and with a minimum interval of ten days between manure application and rainfall. Further studies should also evaluate nitrate leaching.

A estrutura física é uma propriedade essencial para que o solo cumpra adequadamente suas funções e tenha qualidade. Com o objetivo de avaliar a contribuição de práticas de manejo na recuperação da agregação de um solo fisicamente degradado, estudou-se a distribuição de agregados estáveis em água e partículas simples em classes de diâmetro (9,51-4,76; 4,76-2,00; 2,00-0,25; 0,25-0,053; < 0,053 mm) e o estoque de C na camada superficial de 0-7,5 cm de um Argissolo Vermelho distrófico típico da Depressão Central do Rio Grande do Sul sob sistemas de manejo. Em parcelas experimentais com 17 anos, avaliaram-se os sistemas: solo mantido sem plantas e sem revolvimento (Descoberto); plantio direto de Lablab purpureus e milho (Zea mays) (Lablab/m); plantio direto de Cajanus cajan e milho (Guandu/m); e pastagem perene de Digitaria decumbens (Pangola). Em parcelas experimentais com 15 anos, avaliaram-se os sistemas: preparo convencional e plantio direto de Avena strigosa e milho (pc a/m e pd a/m, respectivamente) e Avena strigosa + Vicia sativa e milho + Vigna unguiculata (pc av/mc e pd av/mc, respectivamente). Avaliaram-se, também, área de lavoura de grãos em preparo convencional conduzida por 30 anos (Lavoura) e área de campo nativo (CN), representando a condição degradada e o ecossistema nativo deste solo, respectivamente. As avaliações foram realizadas em amostras de solo indeformadas coletadas em duas épocas (setembro de 1999 e setembro de 2000), compondo seis repetições por sistema de manejo. Os dados foram analisados por meio da análise de variância, e o teste de Tukey (5 %) foi utilizado para verificar as diferenças entre os sistemas de manejo. O CN apresentou 76,4 % de solo agregado, distribuídos em 63,8 % de macroagregados e 23,6 % de partículas simples, com estoque de C de 20,0 Mg ha-1 na profundidade de 0-7,5 cm. O uso agrícola com revolvimento intenso do solo e baixa adição de resíduos (sistema Lavoura) reduziu a proporção de solo agregado para 49,9 % e aumentou a de partículas simples para 50,1 %. O estoque de C reduziu para 11,8 Mg ha-1 na profundidade de 0-7,5 cm. A partir dessa condição, o sistema sem revolvimento de solo, com maior diversidade de espécies de plantas e grande adição de resíduos (pd av/mc) elevou, em 15 anos, a proporção de solo agregado para 70,7 %, e a dos macroagregados, para 53,5 %. A pastagem perene (Pangola) elevou a proporção de solo agregado para 74,1 % e a dos macroagregados para 61,8 %, igualando-se ao CN. Os sistemas pd av/mc, Guandu/m e Lablab/m recuperaram os estoques de C no nível do CN. No entanto, a Pangola, que apresentou os maiores índices de agregação do solo, teve o estoque de C inferior ao desses sistemas, enfatizando a ação positiva do sistema radicular denso na recuperação da agregação do solo.

Soil functions and quality are closely linked to soil structure. The effect of management practices on the recovery of the aggregation of a physically degraded soil was studied based on the distribution of water-stable aggregates and single particles (diameter classes 9.51-4.76, 4.76-2.00, 2.00-0.25, 0.25-0.053, < 0.053 mm) and carbon stock (C) in the surface layer (0-7.5 cm) of a Paleudult in the Central Depression region of the state of Rio Grande do Sul, Brazil, under different management systems. The following systems were evaluated in experimental plots after 17 years: soil without plants and without tillage (fallow); no-till Lablab purpureus and maize (Zea mays) (Lablab/m); no-till Cajanus cajan (pea/m) and maize; perennial pasture of Digitaria decumbens (Pangola grass). The following systems were evaluated after 15 years: conventional tillage and no-till Avena strigosa and maize (CT a/m and NT a/m, respectively) Avena strigosa + Vicia sativa and maize + Vigna unguiculata (CT av/mu and NT av/mu, respectively). A conventionally tilled area was also evaluated after 30 years of grain cultivation (crop) and native grassland (NGr), representing the degraded state and the native ecosystem of this soil, respectively. Undisturbed soil samples collected in two seasons (September 1999 to September 2000) were evaluated in six replications per management system. Data were analyzed by ANOVA and Tukey's test (5 %) to detect differences between management systems. In the NGr, 76.4 % of the soil aggregates consisted of 63.8 % macroaggregates and of 23.6 % of single particles, and a C stock of 20.0 Mg ha-1. The agricultural use with intense soil tillage and low residue application (crop) reduced the proportion of soil aggregates to 49.9 % and raised single particles to 50.1 %, while the C stock decreased to 11.8 Mg ha-1. From this condition, 15 years of the untilled system with greater diversity of plant species and high residue application (NT av/mc) raised the proportion of soil aggregates to 70.7 % and of macroaggregates to 53.5 %. Perennial pasture (Pangola) increased the proportion of soil aggregates to 74.1 % and of macroaggregates to 61.8 %, equaling NGr. The systems NT av/mc, pea/m and Lablab/m recovered C stocks to the level of NGr. Although Pangola had the highest soil aggregation rates, the C stock was lower than in the said systems, emphasizing the positive action of a dense root system in the recovery of soil aggregation.

No início da década de1990, a comunidade científica, consciente da importância do solo para a qualidade ambiental e para a sustentabilidade agrícola, iniciou a abordagem sobre Qualidade do Solo (QS). Este trabalho teve o objetivo de analisar o estado da arte em QS e fazer uma reflexão sobre as propostas de avaliação. A maior parte dos estudos concentra-se na identificação de um índice que seja capaz de servir como indicador de QS (IQS), para auxiliar na avaliação de terras em relação à degradação, fazer estimativas de necessidades de pesquisa e de financiamentos e julgar práticas de manejo utilizadas. Alguns autores propõem os critérios para definição de um IQS. Das abordagens sobre QS, percebe-se que existem três linhas de pensamento: busca por atributos do solo como IQS; matéria orgânica do solo como IQS; e QS como resultado de processos no sistema solo-planta. Conclui-se que o grande avanço nessa área é a abordagem sistêmica do solo, razão pela qual é mais importante identificar como obter QS, do que identificar atributos para medi-la. Sob essa análise, o sistema solo só atinge qualidade quando integrado às plantas e à biota edáfica, e a avaliação do seu funcionamento, que é a própria QS, deve ter como base os princípios da termodinâmica do não-equilíbrio, ciência que rege os sistemas abertos. Os sistemas agrícolas que favorecem a QS são aqueles que cultivam plantas intensamente, de preferência de espécies diferentes, sem o revolvimento do solo.

Soil quality (SQ) has become a major research issue among soil scientists since the early 1990's, following the recognition of the role soils play in terms of agricultural sustainability and environmental quality. This review aims to discuss the state of the art concerning soil quality and look into the proposed indicators for its evaluation. Most part of the research work in the literature is focused on the identification of a soil attribute that would serve as a SQ indicator (SQI) underlying the evaluation of soil degradation and the estimation of research needs and funding, as well as a critical evaluation of soil management practices. Some authors have proposed criteria for the definition of a SQI. In this literature review three major approaches were clearly identified: search for soil attributes to be used as SQI; organic matter as SQI; and SQ as a result of processes in the soil-plant system. It was concluded that the understanding of the soil as a system represents the most significant advance and that therefore the identification of soil management practices to achieve SQ are more important than the effort to obtain a SQ indicator. From this point of view, soil should be treated as an open system where the non-equilibrium thermodynamics theory is applicable and the SQ emerges from the interactions of the soil-plant-biota system. The agricultural systems that enhance SQ are those where the soil is intensively cultivated with plants preferably of different species, and without tilling.