ABSTRACT This study is a historical overview of land governance initiatives implemented in Parana state, Brazil, since the 1970s, ranging from the work carried out by research institutes to government-sponsored programs. These initiatives encouraged the development of technologies and farmers’ widespread adoption of conservation practices. Furthermore, they highlight the factors that brought soil and water conservation to the forefront in discussions on agriculture. This bibliographic review was based on information in research papers and programs developed in Parana. We show that extensive work on management planning and natural resource conservation was undertaken in Parana to strengthen soil governance. The initiatives implemented in watersheds and the development of the no-tillage system represent considerable achievements. However, it was not always that straightforward. As time progressed, the false perception – mainly among farmers – that the erosion problem had been solved led many farmers to neglect soil conservation practices, and in some cases, to abandon agricultural terracing, contour farming, and crop rotation. This resulted in a resurgence of problems related to environmental degradation, aggravating erosion and causing losses of soil and water, with the concomitant environmental damage. In this regard, we describe the means deployed in a new strategy to stimulate a resurgence of effective soil governance based on public policies and public-private partnerships to promote soil and water conservation.

RESUMO O objetivo do estudo é oferecer um resgate histórico do conjunto de ações em governança do solo implementados no estado do Paraná, desde a década de 1970, que vão dos trabalhos desenvolvidos pelos institutos de pesquisa, aos programas governamentais. São ações que possibilitaram o desenvolvimento de tecnologias e a ampla adoção de práticas conservacionistas pelos produtores. Além de indicar os fatores que deram base para a retomada das discussões, em período recente, sobre conservação do solo e da água. Como fontes de informações foram utilizados relatórios de pesquisa e dos programas desenvolvidos no Paraná, empregando o método de revisão histórico-bibliográfica. Verificou-se que foi executado um amplo trabalho de planificação de uso, manejo e conservação dos recursos naturais no Paraná, denotando a construção de uma governança forte em solo e água. Destacam-se no Paraná as ações realizadas em microbacias hidrográficas, pelo pioneirismo do seu enfoque, duração e dimensões, e o desenvolvimento do Sistema Plantio Direto. Contudo, nem tudo foi sempre linear nessa evolução, uma vez que com o passar do tempo foi se constituindo a falsa percepção – principalmente entre os produtores – de que o problema da erosão já estava solucionado. Em consequência disso, muitos agricultores passaram a negligenciar práticas de conservação do solo com uso de terraços, o abandono das operações agrícolas em nível, bem como a rotação de culturas. Tais condutas reavivaram problemas conhecidos e graves de degradação, acentuando os processos de perdas de solo e água pela erosão, e seus prejuízos associados. Neste contexto, descreve-se os instrumentos que estão sendo utilizados em uma nova estratégia paranaense para a retomada de uma efetiva governança do solo, por meio de políticas públicas e de parcerias público-privadas na promoção da conservação de solos e água.

ABSTRACT: Land use and tillage practices may change soil structure and undermine sustainable agriculture; however, such changes are hardly identified in the short term. In this sense, agroforestry systems have been used to reduce soil degradation and promote sustainable production in coffee plantations. These areas are expected to have well-structured soils and hence improved root distribution. This study aimed to evaluate soil quality by the morphostructural and root distribution analyses comparing open-grown coffee and coffee in agroforestry systems with rubber trees for 19 years, in an Oxisol in northern Paraná State (Brazil). Treatments consisted of open-grown coffee (OG), coffee partially shaded by rubber trees (PSH), and coffee fully shaded by rubber trees (FSH). The mapping of morphostructural features and soil resistance to penetration in “cultural profile” walls identified changes in soil structure resulting from different tillage systems. Root distribution was better in coffee plants grown in PSH and FSH systems. At greater depths, cultural profiles of FSH and PSH showed a larger numbers of roots compared to OG. Among the three systems, PSH provided a better environment for root growth and distribution. This result could be attributed to the high biological activity and interaction between roots and aggregates in that profile. The FSH agroforestry system provided less compact morphological structures and more roots throughout the soil profile. The agroforestry systems presented fewer soil structural changes by tillage operations and lower values of soil penetration resistance. Coffee root distribution was an effective indicator of soil quality and consistent with the morphostructural characterization of cultural profile.

Resumo: O objetivo deste trabalho foi avaliar o efeito de diferentes sistemas de manejo sobre o grau de dispersão de argila e sua relação com os atributos químicos do solo e o índice de qualidade participativo (IQP) do sistema plantio direto, em áreas de microbacias do Oeste do Paraná. Os sistemas de manejo avaliados foram: sistema plantio direto; plantio direto com sucessão de culturas; plantio direto com revolvimento do solo; e sistema convencional. Além disso, os sistemas de manejo foram avaliados quanto ao seu IQP. Amostras de solo foram coletadas a 0,0-0,20 m de profundidade do solo, em 40 áreas agrícolas e em 6 matas nativas tidas como referências. Foram avaliados grau de dispersão de argila, carbono orgânico total, pH (em CaCl2), potássio trocável (K+), fósforo disponível (P), cálcio e magnésio trocáveis (Ca2++Mg2+), e acidez potencial (H+Al3+). Ajustou-se um modelo de regressão linear múltipla pelo método dos mínimos quadrados. Realizou-se a comparação de médias do grau de dispersão de argila, por microbacia, a 5% de probabilidade. Os sistemas de manejo foram comparados pelo teste de Scott-Knott. Os atributos químicos do solo apresentaram maior influência sobre a dispersão da argila do que os diferentes sistemas de manejo avaliados. O sistema plantio direto integral apresentou o maior teor de carbono orgânico, que foi semelhante ao das áreas nativas. O sistema convencional e o plantio direto com revolvimento do solo apresentaram menor IQP e maiores taxas de dispersão de argila do que as áreas sob sistema plantio direto integral. O IQP permite diferenciar os sistemas de manejo convencional e plantio direto.

Abstract: The objective of this work was to evaluate the effect of different farm systems on clay dispersion and its relationship with soil chemical properties and the no-tillage system participatory quality index (IQP), in watershed areas in the west of the state of Paraná, Brazil. The farm systems evaluated were: no-tillage; no-tillage with crop succession; no-tillage with soil disturbance; and conventional system. In addition, the farm systems were evaluated for their IQP. Soil samples were collected at 0.0-0.20-m soil depth, in 40 agricultural areas and in 6 native forests considered as references. The degree of clay dispersion, total organic carbon, pH (CaCl2), exchangeable potassium (K+), available phosphorus (P), exchangeable calcium and magnesium (Ca2++Mg2+), and potential acidity (H+Al3+) were determined. A linear multiple regression model was fitted by the method of least squares. The averages of clay dispersion degree per watershed were compared at 5% probability. The farm systems were compared by Scott-Knott’s test. Soil chemical properties showed a higher influence on clay dispersion than the different farm systems assessed. The no-tillage system alone showed the highest content of organic carbon, which was similar to those of the native areas. The conventional system and the no-tillage system with soil disturbance showed a lower IQP and a higher degree of clay dispersion than the areas with the no-tillage system alone. The IQP allows distinguishing the conventional system from the no-tillage system.

ABSTRACT Retaining sugarcane straw over the soil after harvesting can improve soil structure and increase soil carbon stabilization, mainly in macroaggregates. We evaluated the carbon content in the aggregate classes in areas under burn and no-burn (adopted for five years) sugarcane management systems, focusing on the superficial layer (0.00-0.20 m). The experiment was carried in an Oxisol and the treatments consisted in burnt sugarcane, manual harvest; burnt sugarcane, mechanized harvest; and no-burn, mechanized harvest. The retention of sugarcane straw on the soil surface is justified by the increase in carbon content and carbon stock in the surface layer (0.00-0.20 m) by restructuring of the soil, even though it cannot match the structure of the soil under native forest. Our results suggest that in no-burn management the carbon not occluded inside aggregates was important to increase carbon stabilization in soil and that more attention should be given to macroaggregates 2.00-8.00 mm present in this management system, that showed higher carbon content and was responsible for increase of the geometric and weight diameter, increasing the erosion resistance in the long term in relation to burn systems.

ABSTRACT Soil and crop management systems change the soil structure, thereby affecting soil quality. The “profil cultural” method (PCM) has been used to identify the effects of management systems on soil structure; however, few studies relate the structures identified by the PCM to quantitative indicators of soil structural quality. This study aimed to quantify soil structures using the PCM and relate these structures to bulk density (Bd), critical bulk density (Bdc), soil aeration capacity (εa), least limiting water range (LLWR), and soil air permeability (Ka) under different soil and crop management systems. The study was developed in a long-term experiment (24 years) involving two systems of soil management (no-tillage and conventional tillage) and two systems of crop management (rotation and succession), resulting in four treatments: no-tillage with crop rotation (NTr), no-tillage with crop succession (NTs), conventional tillage with heavy harrowing and crop rotation (CTr) and conventional tillage with heavy harrowing and crop succession (CTs). The PCM was used to identify the different homogeneous morphological units (HMUs) in the soil profile. Undisturbed soil samples were collected for the HMUs that were most represented in the profiles to determine Ka, LLWR, Bd, and εa. There was agreement between the HMUs and the quantitative indicators. The LLWR showed greater values for Bdc under no-tillage (NTr = 1.36 Mg m-3 and NTs = 1.37 Mg m-3) than under conventional tillage (CTs = 1.31 Mg m-3 and CTr = 1.33 mg m-3). The proportion of samples where Bd > Bdc was 23 % under CTs, 77 % under CTr, 32 % under NTs, and 39 % under NTr. The structures that were most restrictive to root development (CΔ, CΔμ, FmtΔμ, and FmtμΔ) show a lower Ka and greater soil penetration resistance as the soil dries. Pores are more continuous and the structure is less restrictive to plant development in no-tillage than in conventional tillage.

ABSTRACT Soil structure plays an important role in water retention, infiltration capacity, porosity, and penetration resistance. The aim of this study was to evaluate the unsaturated hydraulic conductivity and physical properties of Oxisol soils (bulk density and macro-, micro-, and total porosity) in the structures identified using the profil cultural method in areas under two different management practices (perennial pasture and sugarcane). Three pits were dug in each plot to find out how homogeneous morphological structural units (HMSU) were organized in the soil. Next, unsaturated hydraulic conductivity (Ki) was measured in situ inside each HMSU using a triple-ring infiltrometer at multiple suction. Six samples were collected (two samples for each kind of structural organization in each pit) to determine soil bulk density, total porosity, and macro- and microporosity. Each management practice resulted in a distribution of structures in the soil profile. The behavior of morphologically similar clods was the same, regardless of the physical manipulation of the soil. The distribution of structures based on the management practice determines specific hydraulic conductivities in the soil profile.

Resumo O objetivo deste trabalho foi avaliar o emprego da espectroscopia de infravermelho próximo (NIRS) para a predição de formas de P, C e N, em solos desenvolvidos de basalto, com uso de modelos multivariados e de amostras com diferentes granulometrias. Amostras de Latossolos e Nitossolos provenientes de áreas de cultivo, pastagem e vegetação nativa foram coletadas nas camadas de 0,0-0,20 e de 0,60-0,80 m, e analisadas quanto aos teores de P disponível, P remanescente, C orgânico, C total e N total. Os espectros na região entre 1.100 e 2.500 nm foram obtidos de amostras com granulometria menor do que 2,0 e 0,2 mm. Modelos multivariados de predição foram construídos e validados a partir dos resultados obtidos pelos métodos de referência e dos espectros. O peneiramento das amostras em malha de 0,2 mm melhorou a relação entre os comprimentos de onda no NIRS e os teores de C orgânico, C total e N total no solo, o que permitiu a obtenção de melhores modelos de calibração e predição para esses atributos. Independentemente do tamanho das partículas, os modelos não apresentam robustez, acurácia e precisão adequadas de predição para o P extraível e o P remanescente.

Abstract The objective of this work was to evaluate the use of near-infrared spectroscopy (NIRS) to predict P, C, and N forms in soils developed from basalt, using multivariate models and soil samples with different granulometries. Samples from Oxisols and Alfisols from croplands, pasture, and native vegetation areas were collected at the 0.0-0.20 and 0.60-0.80-m soil layers, and analyzed for contents of available P, remaining P, organic C, total C, and total N. Spectra in the region between 1,100 and 2,500 nm were obtained on samples with granulometry smaller than 2.0 and 0.2 mm. Multivariate prediction models were constructed and validated from the results obtained by the reference methods and spectra. Sample screenings through 0.2 mm mesh improved the relationship between wavelengths in NIRS and the contents of organic C, total C, and total N in the soil, which allowed better calibration and prediction models for these attributes. Irrespectively of particle sizes, the models did not show appropriate robustness, accuracy, and precision for extractable P and remaining P.

O objetivo deste estudo é estimar custos da erosão hídrica associados às perdas de nutrientes em quatro taxas de cobertura artificial do solo. O experimento foi conduzido de 1987 a 1996, em talhões coletores de perdas por erosão, em Campinas (SP), em Latossolo Vermelho distroférrico, sob chuva natural. O delineamento experimental foi inteiramente ao acaso, com quatro tratamentos (taxas de cobertura do solo: 0%, 24%, 40% e 90%) e três repetições. Para estimar os custos, os teores de P, K+, Ca2+ e Mg2+ na água da enxurrada e na terra carreada pela erosão foram somados, convertidos em superfosfato triplo, cloreto de potássio e calcário dolomítico, e multiplicados pelos seus preços de mercado. Os resultados indicam, para as condições experimentais, que quanto maior o percentual de cobertura do solo, menores as perdas de água, terra, matéria orgânica e nutrientes. O solo com 90% de cobertura, em comparação àquele com 0%, reduziu as perdas médias de água em 51,97%, de terra em 54,44% e de matéria orgânica em 54,91%. Em solo sem cobertura, foram estimadas perdas de 16% de P2O5 e 8% de KCl em relação à quantidade de fertilizantes recomendada. Os custos variaram de US$ 107,76 ha–1 ano–1 no solo com 0% de cobertura a US$ 18,15 ha–1 ano–1 no solo com 90%. A partir desses valores, estimaram-se para o Brasil perdas de 616,5 milhões de toneladas de terra ao ano, decorrentes do processo de erosão do solo em lavouras anuais, e custos da ordem de US$ 1,3 bilhão ao ano.

The aim of this study was to estimate water erosion costs associated with nutrient losses in four different rates of artificial cover. The experiment was carried out from 1987 to 1996 in runoff plots to measure soil losses in Campinas, State of Sao Paulo, in an Ferralsol under natural rainfall. The experimental design was completely randomized, with four treatments (0%, 24%, 40% and 90% artificial cover) and three replications. To estimate costs, P, K+, Ca2+ and Mg2+ concentrations in runoff water and soil removed by erosion were summed up, converted into triple superphosphate, potassium chloride and dolomitic limestone and multiplied by their respective market prices. The results indicate that, under the experimental conditions, the greater the percentage of soil cover, the lower the losses of water, soil, organic matter and nutrients. The soil with 90% cover presented reduction of 51.97% in average water losses, 54.44 in soil losses and 54.91% in organic matter losses than the treatment with 0% cover. In bare soil, losses were estimated at 16% P2O5 and 8% KCl in terms of the amount of fertilizers recommended. Costs varied from US$ 107.76 ha–1 year–1 in bare soil (0% cover) to US$ 18.15 ha–1 year–1 in soil with 90% cover. With these values, losses were estimated at 616.5 million tons of soil per year for Brazil, as a result of soil erosion in annual crops, and cost of this process is around US$ 1.3 billion per year.

The objective of this study was to evaluate the relationships between the spectra in the Vis-NIR range and the soil P concentrations obtained from the PM and Prem extraction methods as well as the effects of these relationships on the construction of models predicting P concentration in Oxisols. Soil samples' spectra and their PM and Prem extraction solutions were determined for the Vis-NIR region between 400 and 2500 nm. Mineralogy and/or organic matter content act as primary attributes allowing correlation of these soil phosphorus fractions with the spectra, mainly at wavelengths between 450-550, 900-1100 nm, near 1400 nm and between 2200-2300 nm. However, the regression models generated were not suitable for quantitative phosphate analysis. Solubilization of organic matter and reactions during the PM extraction process hindered correlations between the spectra and these P soil fractions. For Prem,, the presence of Ca in the extractant and preferential adsorption by gibbsite and iron oxides, particularly goethite, obscured correlations with the spectra.

O sistema de integração lavoura-pecuária (ILP) tem se evidenciado como alternativa viável para a recuperação e manutenção das características do solo. Este estudo foi desenvolvido em um experimento de ILP conduzido pelo Instituto Agronômico do Paraná no município de Xambrê, PR, com diferentes intensidades de pastejo. O objetivo deste trabalho foi avaliar o carbono da biomassa microbiana (CBM) e a atividade enzimática no solo, em sistema de integração lavoura-pecuária com soja cultivada no verão e Brachiaria ruziziensis no inverno, sendo esta submetida a diferentes intensidades de pastejo. Os tratamentos constaram de diferentes alturas de pasto e intensidades de pastejo: 10; 20; 30; e 40 cm (IP-10, IP-20, IP-30 e IP-40, respectivamente) e uma área sem pastejo (SP). Os atributos microbiológicos analisados foram CBM, respiração microbiana (RM), quociente metabólico (qCO2), atividade das enzimas fosfatase ácida, β-glucosidase, arilsulfatase, celulase e hidrólise do diacetato de fluoresceína (FDA). Após o segundo ciclo da pastagem, o tratamento IP-20 (intensidade moderada de pastejo 20 cm) apresentou os maiores teores de CBM e os menores de qCO2. Após o segundo ciclo da soja, o tratamento com maior intensidade de pastejo IP-10 demonstrou o menor teor de CBM. Os teores de CBM do solo na pastagem foram favorecidos pela inserção dos animais no sistema. A alta intensidade de pastejo (10 cm de altura da pastagem) durante o ciclo da pastagem pode provocar redução no C microbiano do solo, com efeito negativo sobre a mesma na cultura sucessora. Entre as enzimas avaliadas, somente a arilsulfatase e celulase foram sensíveis para avaliar o manejo ILP, com diferenças entre os tratamentos com intensidade moderada de pastejo (IP-20) e a área sem pastejo.

Integrated crop-livestock systems (ICLs) are a viable strategy for the recovery and maintenance of soil characteristics. In the present study, an ICL experiment was conducted by the Instituto Agronômico do Paraná in the municipality of Xambre, Parana (PR), Brazil, to evaluate the effects of various grazing intensities. The objective of the present study was to quantify the levels of microbial biomass carbon (MBC) and soil enzymatic activity in an ICL of soybean (summer) and Brachiaria ruziziensis (winter), with B. ruziziensis subjected to various grazing intensities. Treatments consisted of varying pasture heights and grazing intensities (GI): 10, 20, 30, and 40 cm (GI-10, GI-20, GI-30, and GI-40, respectively) and a no grazing (NG) control. The microbial characteristics analysed were MBC, microbial respiration (MR), metabolic quotient (qCO2), the activities of acid phosphatase, β-glucosidase, arylsuphatase, and cellulase, and fluorescein diacetate (FDA) hydrolysis. Following the second grazing cycle, the GI-20 treatment (20-cm - moderate) grazing intensity) contained the highest MBC concentrations and lowest qCO2 concentrations. Following the second soybean cycle, the treatment with the highest grazing intensity (GI-10) contained the lowest MBC concentration. Soil MBC concentrations in the pasture were favoured by the introduction of animals to the system. High grazing intensity (10-cm pasture height) during the pasture cycle may cause a decrease in soil MBC and have a negative effect on the microbial biomass during the succeeding crop. Of all the enzymes analyzed, only arylsuphatase and cellulase activities were altered by ICL management, with differences between the moderate grazing intensity (GI-20) and no grazing (NG) treatments.

Avaliaram-se os efeitos de diferentes culturas de inverno sobre indicadores de qualidade associados aos ciclos do C e do N e frações de C em um Nitossolo Vermelho eutroférrico, sob plantio direto em implantação, em dois anos agrícolas, em Londrina PR. O delineamento experimental foi em blocos ao acaso, com parcelas subdivididas no tempo, com quatro repetições. As parcelas foram constituídas pelas culturas de inverno: consórcio de aveia preta (Avena strigosa), ervilhaca peluda (Vicia villosa) e nabo forrageiro (Raphanus sativus); girassol (Helianthus annuus) consorciado com braquiária (Urochloa ruziziensis); milho (Zea mays) consorciado com braquiária; e as culturas solteiras de milho; nabo forrageiro; ou trigo (Triticum aestivum). As subparcelas foram os anos de avaliação: 2008 e 2009. Determinaram-se os teores de C total, C lábil e resistente, o N total, o C e o N da biomassa microbiana, a relação C/N da matéria orgânica do solo, e o quociente microbiano do solo (qMic), além de atributos microbiológicos e bioquímicos apenas no segundo ano. Os atributos foram significativamente alterados pelas culturas de inverno, sobretudo o consórcio de plantas de cobertura e nabo forrageiro, e pelas épocas de avaliação. Apesar de estimular a atividade microbiológica/bioquímica do solo, o cultivo de nabo diminuiu o teor de C do solo no segundo ano, similarmente ao cultivo de trigo. A combinação de espécies de plantas de cobertura de inverno é uma alternativa de manejo no estabelecimento do sistema de plantio direto, contribuindo para o aumento dos teores de C e estimular a atividade microbiológica/bioquímica do solo.

We assessed the effect of different winter crops on indicators of soil quality related to C and N cycling and C fractions in a Rhodic Kandiudult under no-till system at implantation, during two growing seasons, in Londrina PR Brazil. The experimental design was randomized blocks with split-plot in time arrangement, with four replications. The parcels were the winter crops: multicropping of cover crops with black oat (Avena strigosa), hairy vetch (Vicia villosa) and fodder radish (Raphanus sativus); sunflower (Heliantus annuus) intercropped with Urochloa ruziziensis; corn (Zea mays) intercropped with Urochloa; and corn; fodder radish; or wheat (Triticum aestivum) as sole crops. The subplots were the years: 2008 and 2009. Determinations consisted of total organic C, labile and resistant C, total N, microbial biomass C and N, the C/N ratio of soil organic matter, and the microbial quotient (qMic), besides microbiological and biochemical attributes, assessed only in 2009. The attributes significantly changed with the winter crops, especially the multicropping of cover crops and fodder radish, as well as effect of years. Despite stimulating the microbiological/biochemical activity, fodder radish cropping decreased the soil C in the second year, likewise the wheat cropping. The multicropping of cover crops in winter is an option for management in the establishment of no-till system, which contributes to increase the concentrations of C and stimulate the soil microbiological/biochemical activity.

A percepção do problema da erosão do solo, nas pesquisas brasileiras em ciências agrárias, vem sendo relatada desde o século XIX. Nesse contexto, o objetivo deste trabalho foi realizar uma revisão histórica dos marcos institucionais que fomentaram as pesquisas em erosão do solo no Brasil e deram início às pesquisas agrícolas no país. Ao longo do século XIX e início do século XX, observaram-se a criação de jardins botânicos, instituições executivas, institutos de pesquisa, estações experimentais e instituições de ensino e a elaboração e diversificação de periódicos de comunicação técnico-científica. Esses estabelecimentos atuaram, cada qual a sua maneira, nas pesquisas em erosão do solo no Brasil. No período Imperial (1808-1889), as discussões se concentravam no esgotamento do solo e na manutenção da fertilidade das terras agrícolas. Na Primeira República (1889-1930), com a criação de várias instituições de ensino e com a consolidação do Instituto Agronômico nas pesquisas sobre a degradação dos solos, os estudos se pautaram na discussão sobre o depauperamento do solo, na identificação dos principais fatores geradores do processo de erosão e nas medidas necessárias para o seu controle. No Estado Novo (1930-1945), foram desenvolvidas e disseminadas inúmeras práticas de conservação do solo para combater a erosão, implantando-se experimentos para medir o volume das perdas, principalmente de terra e água por erosão hídrica. Na República Nova (1945-1964), experimentos foram instalados em praticamente todas as regiões do país. A conservação do solo e a da água se consolidaram como uma das principais áreas da Ciência do Solo no Brasil. Eventos científicos começaram a ser realizados sobre a temática. A pós-graduação foi instituída no país. No Regime Militar (1964-1985), muitas instituições de pesquisa e ensino foram criadas e os trabalhos experimentais foram intensificados. Nesse período, o processo de erosão do solo atingiu patamares alarmantes e o sistema de Plantio Direto foi desenvolvido no país.

The problem of soil erosion in Brazil has been a focus of agricultural scientific research since the 19th century. The aim of this study was to provide a historical overview of the institutional landmarks which gave rise to the first studies in soil erosion and established the foundations of agricultural research in Brazil. The 19th century and beginning of the 20th century saw the founding of a series of institutions in Brazil, such as Botanical Gardens, executive institutions, research institutes, experimental stations, educational institutions of agricultural sciences, as well as the creation and diversification of scientific journals. These entities, each in its own way, served to foster soil erosion research in Brazil. During the Imperial period (1808-1889), discussions focused on soil degradation and conserving the fertility of agricultural land. During the First Republic (1889-1930), with the founding of various educational institutions and consolidation of research on soil degradation conducted by the Agronomic Institute of Campinas in the State of São Paulo, studies focused on soil depletion, identification of the major factors causing soil erosion and the measures necessary to control it. During the New State period (1930-1945), many soil conservation practices were developed and disseminated to combat erosion and field trials were set up, mainly to measure soil and water losses induced by hydric erosion. During the Brazilian New Republic (1945-1964), experiments were conducted throughout Brazil, consolidating soil and water conservation as one of the main areas of Soil Science in Brazil. This was followed by scientific conferences on erosion and the institutionalization of post-graduate studies. During the Military Regime (1964-1985), many research and educational institutions were founded, experimental studies intensified, and coincidently, soil erosion reached alarming levels which led to the development of the no-tillage system.

Soil is an essential natural resource for humans and an important part of the environment. However, soil is often used and managed inappropriately, causing its erosion and degradation, with concomitantly negative social, political and economic impacts. This study aimed to discuss sustainable development; and losses and problems caused by soil erosion, and to suggest a model for assessing erosion costs. The relevance of economic models for costing soil erosion is stressed. Based on an economic theory, it presents a procedure for assessing economic costs of soil erosion, centered on the on-site and off-site costs that are generated. The physical processes of soil erosion are described and their economic effects reviewed, drawing on theoretical and empirical sources. Limited data and information is available on the economic losses resulting from erosion, which hampers assessment and valuation.

Considerando que a agregação reflete na interação dos fatores químicos, físicos e biológicos dos solos, o objetivo deste trabalho foi avaliar a agregação de um Latossolo Vermelho distroférrico sob plantio direto (PD) e preparo convencional (PC) implantado há mais de 20 anos, utilizando-se como referência do estado natural uma mata nativa (M). Após análise do perfil de solo pelo método do perfil cultural nas áreas sob manejo e mata, foram coletadas amostras nas profundidades de 0-5, 5-10, 10-20 e 20-40 cm de profundidade, com seis repetições. A partir dessas amostras, foram determinados o índice de estabilidade dos agregados (IEA), o diâmetro médio ponderado (DMP), o diâmetro médio geométrico (DMG) e as classes de diâmetro >8, 8-4, 4-2, 2-1, 1-0,5, 0,5-0,25 e < 0,25 mm, além das determinações físicas (granulometria, argila dispersa em água - AD, índice de floculação - IF e densidade do solo - Ds) e químicas (carbono orgânico total - COT, nitrogênio total - N, cálcio trocável - Ca2+ e pH). Os resultados indicaram que o aumento da mobilização do solo (M < PD < PC) resultou em diminuição da sua estabilidade, medida por meio de todos os indicadores de estabilidade analisados: DMP, DMG, IEA, distribuição de classes de agregados, AD e IF, concluindo-se pela validade deles em estudos de agregação do solo considerado.

Considering that the soil aggregation reflects the interaction of chemical, physical and biological soil factors, the aim of this study was evaluate alterations in aggregation, in an Oxisol under no-tillage (NT) and conventional tillage (CT), since over 20 years, using as reference a native forest soil in natural state. After analysis of the soil profile (cultural profile) in areas under forest management, samples were collected from the layers 0-5, 5-10, 10-20 and 20-40 cm, with six repetitions. These samples were analyzed for the aggregate stability index (ASI), mean weighted diameter (MWD), mean geometric diameter (MGD) in the classes > 8, 8-4, 4-2, 2-1, 1-0.5, 0.5-0.25, and < 0.25 mm, and for physical properties (soil texture, water dispersible clay (WDC), flocculation index (FI) and bulk density (Bd)) and chemical properties (total organic carbon - COT, total nitrogen - N, exchangeable calcium - Ca2+, and pH). The results indicated that more intense soil preparation (M < NT < PC) resulted in a decrease in soil stability, confirmed by all stability indicators analyzed: MWD, MGD, ASI, aggregate class distribution, WDC and FI, indicating the validity of these indicators in aggregation analyses of the studied soil.

O objetivo deste trabalho foi identificar atributos de solo importantes para a estimativa do índice de estabilidade de agregados. Para a identificação dos atributos, utilizou-se a regressão múltipla "stepwise" em dados coletados de Latossolo Vermelho eutroférrico, cultivado em sistema de plantio direto. Para a obtenção dos modelos de estimativa do índice de estabilidade de agregados (IeaE), foram analisadas dez variáveis independentes: argila total, densidade do solo, resistência à penetração, matéria orgânica, pH em água, capacidade efetiva de troca de cátions, água disponível, volume total de poros, macroporosidade e umidade gravimétrica. Os atributos argila total (Arg), densidade do solo (Ds), resistência à penetração (RP), matéria orgânica (MO) e pH são os mais importantes para a estimativa do IeaE, e a função de pedotrânsferência que melhor descreve esse índice é: IeaE = 27,80 + 0,04Arg + 27,97Ds + 12,35RP + 0,45MO - 9,72pH (R² = 0,89).

The objective of this work was to identify the most important soil attributes to estimate the aggregate stability index. To identify these attributes, multiple stepwise regression was used on data collected from an Eutrorthox cultivated under a no-tillage system. To obtain the prediction models for the aggregate stability index (IeaE), ten independent variables were evaluated: total clay, bulk density, penetration resistance, organic matter, pH in water, effective cation exchange capacity, available water, total porosity, macroporosity, and gravimetric moisture. The attributes total clay (Arg), bulk density (Ds), penetration resistance (RP), organic matter (MO), and pH are the most important for the estimation of the IeaE, and the pedotransfer function that best describes this index is: IeaE = 27.80 + 0.04Arg + 27.97Ds + 12.35RP + 0.45MO - 9.72pH (R² = 0.89).