ABSTRACT Potassium (K) vertical mobility in soils has often been overestimated and used as a rationale for recommending the broadcast application of this nutrient in fertility management programs, especially in soils with low cation exchange capacity (CEC). This study aimed to evaluate the vertical distribution of K in two land uses: areas with natural vegetation and crop fields managed under no-tillage (NT) fertilized with K. For this purpose, 49 soil profiles from the Brazilian subtropical state of Rio Grande do Sul were sampled, comprising 45 profiles from areas under NT management and four profiles from sites with natural vegetation. Soil samples were collected in 19 very thin layers: 1 cm layer in the first 10 cm, 2.5 cm layer from 10 to 25 cm, and 5 cm layer from 25 to 40 cm. Sampling sites were then grouped according to their CEC, categorized as < 7.5, 7.6-15.0, and 15.1-30.0 cmolc dm-3. Both crop fields and natural fields exhibit a similar vertical gradient model, characterized by a strong accumulation of K in the soil within the uppermost centimeters. This gradient is notably enhanced by the addition of K fertilizers, leading to a substantial portion of K becoming inaccessible to the root system. The optimal level of available K for the topsoil soils was found within an average range of 4 to 12.5 cm of soil depth. Consequently, K fertilization resulted in two main outcomes: (i) an excess of K in the upper soil layers, which increases the potential for K loss through surface erosion and runoff, and (ii) a limited migration of K towards the deeper soil layers until reaching the root growth zone. There is an urgent need to: (a) reaffirm the official recommendations of public agencies that the replacement of K exported by crops should be carried out in the furrow, along the sowing line, and as deep as possible; and (b) reconsider the diagnostic soil layer for assessing the status of K availability in soils under NT management. (K programs CEC. CEC . (CEC) uses notillage no tillage (NT purpose sampled 2 2. 75 7 7.5 7.615.0, 76150 7.6 15.0, 6 15 0 7.6-15.0 15.130.0 151300 15.1 30.0 30 15.1-30. dm3. dm3 dm 3. 3 dm-3 model centimeters fertilizers system 125 12 12. depth Consequently outcomes i (i runoff ii (ii zone (a furrow line possible b (b (CEC 7. 615 7.615.0 7615 76 150 15.0 7.6-15. 130 15.130. 15130 151 15. 300 30. 15.1-30 dm- 61 7.615. 761 7.6-15 13 15.130 1513 15.1-3 7.615 7.6-1 15.13 15.1- 7.61 7.6-

ABSTRACT Bases are chemical species that donate electrons, accept protons, or release hydroxyls (OH–) in aqueous solution. In Soil Science, “base saturation”, “exchangeable bases” or “basic cations” has been widely used to distinguish Ca2+, Mg2+, Na+, and K+ from H+ and Al3+ cations. This terminology is confusing since none of these cations are truly a base in chemistry sense. However, in the absence of the proposition of a correct term, the term “base saturation” remains in use nowadays, causing confusion among students, professionals, and even among professors and researchers in Soil Science, as it leads to the erroneous interpretation that the soil acidity can be corrected by adding these cations to the soil. Here, we present the historical background of this nomenclature and a theoretical foundation that justifies the abolition of the use of these terms in Soil Science. We consider that the most correct is to call it “Ca-Mg-K-Na saturation”, which, despite being long, would refer directly and without any misinterpretation of the terminology. In Soil Fertility, the “base saturation” is often calculated only as a function of the sum of Ca, Mg, and K, since the Na content is negligible in most tropical and subtropical soils. Thus, one could use the term “Ca-Mg-K saturation”. Likewise, it is also suggested to abolish the use of the term “sum of bases” and use the term “sum of Ca-Mg-K” or “sum of Ca-Mg-K-Na” instead when necessary.

ABSTRACT The reduction of water quality typically starts in small streams and rivers; tributaries interconnected to major rivers. In this regard, this study aimed to investigate waste disposal of small wine and liquor agribusinesses by monitoring the water quality of two streams, tributaries of the Soturno and Jacuí rivers, located in the Quarta Colônia region the state of Rio Grande do Sul (RS), Brazil. We began monitoring water quality in July 2008 and continued uninterruptedly until May 2009. We collected water samples at three different locations (source, upstream, and downstream) in triplicate, totaling 162 samples. We investigated 24 variables that makeup chemical, physical and biological parameters of water quality. With the results, we concluded that the diffuse sources of pollution in the "Liquor stream" are associated with wastewater of small agribusinesses and nearby residences, in contrast, the source of the "Wine stream" showed the most chemical changes in water quality, and whose diffuse sources of pollution are more associated with agricultural activity than the small agribusinesses activity. The variables of chemical and biological oxygen demand, dissolved oxygen, total iron, total manganese, and total phosphorus presented values higher than those of Class II waters in both streams. Therefore, small agribusinesses need to adequately dispose of the waste in order to meet existing legislation comprehensively.

RESUMEN La reducción de la calidad del agua por lo general comienza en pequeños arroyos y ríos; afluentes que están interconectados para llegar a los principales cauces. Este estudio tiene como objetivo investigar la disposición de residuos en la pequeña agroindustria de vinos y licores en afluentes del Río Soturno y Río Jacuí. Las corrientes que reciben los residuos de las actividades agroindustriales (licores y vinos), ubicado en la región de la cuarta colonia de inmigrantes italianos en Rio Grande do Sul / Brasil fueron monitoreadas. Este proceso comenzó en 07/2008 y continuó ininterrumpidamente hasta 05/2009. Las muestras de agua fueron recolectadas en tres puntos diferentes (al este, aguas arriba y abajo) por triplicado, por un total de 162 muestras. Se investigaron 24 que componen los parámetros químicos, físicos y biológicos de la calidad del agua. Con los resultados, concluimos que las fuentes difusas de contaminación en la “Corriente de licor” están asociadas con aguas residuales de pequeños agronegocios y residencias cercanas, en contraste, la fuente de la “Corriente del vino” mostró la mayor cantidad de cambios químicos en la calidad del agua, y cuyas fuentes difusas de contaminación están más asociadas a la actividad agrícola que a la pequeña actividad agroindustrial. Las variables de demanda química y biológica de oxígeno, oxígeno disuelto, hierro total, manganeso total y fósforo total presentaron valores superiores a los de las aguas Clase II en ambos arroyos. Por lo tanto, las pequeñas empresas agrícolas deben eliminar adecuadamente los desechos para cumplir de manera integral la legislación existente.

ABSTRACT Identification of areas with potential contamination of water courses by phosphorus (P) can be carried out through methodologies such as the Phosphorus Index (IP). However, the validation of the best model is necessary for the construction of risk scenarios for environmental contamination. The objective of this work was to verify the adjustment of three IP versions in the estimation of the vulnerability of the potential loss of P in a rural river basin. The basin area is 79.5 ha and is located in the municipality of Júlio de Castilhos, Rio Grande do Sul, Brazil. Three versions of IP were used to estimate the transfer of P to water courses. The validation of the models was made based on the actual P results in the soil and by the measured in the analysis of the runoff in the watershed exudation. Subsequently, a scenario was simulated where P levels in the soil were adequate to obtain high yields. The three versions of the IP presented variations in the estimate of the potential loss of phosphorus. The actual and estimated data showed low loss of soil and P and was attributed to the soft relief to the slightly undulated, the presence of wetlands in the convergent slopes, to the soil management and to the low level of available P. The Alabama IP version presented a better estimate of the vulnerability of soil P loss to watercourses. However, the IP version of Nebraska more realistically predicts the transfer of P to aquatic systems when using doses of P suitable for high yields.

RESUMO Identificação de áreas com potencial de contaminação dos cursos hídricos por fósforo (P) pode ser realizada através de metodologias como o Índice de Fósforo (IP). No entanto, a validação do melhor modelo faz-se necessária para a construção de cenários de risco de contaminação ambiental. O objetivo deste trabalho foi verificar o ajuste de três versões do IP na estimativa da vulnerabilidade da perda potencial de P em uma bacia hidrográfica rural. A área da bacia é de 79,5 ha e localizada no município de Júlio de Castilhos, Rio Grande dos Sul, Brasil. Para a estimativa de transferência de P aos cursos hídricos utilizaram-se três versões do IP. A validação dos modelos foi feita com base nos resultados reais de P no solo e pelo mensurado em análises da enxurrada no exutório da bacia hidrográfica. Posteriormente foi simulado um cenário em que os níveis de P no solo fossem adequados a obtenção de altas produtividades. As três versões do IP apresentaram variações na estimativa da perda potencial de fósforo. Os dados reais e estimados evidenciaram baixa perda de solo e de P e foi atribuída ao relevo suave à levemente ondulado, a presença de áreas úmidas nas vertentes convergentes, ao manejo do solo e ao baixo nível de P disponível. A versão do IP do Alabama apresentou melhor estimativa da vulnerabilidade da perda de P do solo para os cursos hídricos. No entanto, a versão do IP de Nebraska prevê mais realisticamente a transferência de P aos sistemas aquáticos quando se usara doses de P adequadas às altas produtividades.

ABSTRACT In Southern Brazil, agricultural soils are often treated over long periods with annual pig slurry (PS) applications, and their influence on soil nutrient dynamics should be monitored. This study aimed to evaluate the P forms accumulated in the soil and some biological and biochemical parameters of the P cycle after 19 successive PS applications over eight years, in a no-tillage (NT) system. Pig slurry was applied at rates of 0, 20, 40, and 80 m3 ha-1 per crop. Several P forms (available P, microbial P, phosphatase enzyme, total organic and inorganic P) in the 0.00-0.05 and 0.05-0.10 m soil layers were analyzed. Increases up to 5,523 % in available P, 308 % in microbial P, 104 % in phosphatase enzyme activity, 91 % in organic P, 251 % in inorganic P, and 19 % in Total-P were observed in the 0.00-0.05 m soil layer in response to the highest PS rate compared to the treatment with no PS. Results also indicated that P added via PS was preferentially accumulated in the inorganic fractions (83-98 %). The increase in organic P was limited by the increase in soil organic carbon. The increase in soil microbial biomass-P was more influenced by available P, while the increase in phosphatase enzyme activity was more related to the increase in organic P and C. Therefore, PS applied to the soil affected the chemical, biological, and biochemical components of the soil P cycle. Results indicate that even half of the PS rate normally used by farmers (20 m3 ha-1) poses a high risk of pollution of water bodies by runoff from these soils.

ABSTRACT Phosphorus (P) fractionation is a suitable procedure to ascertain P lability in sediments and is able to distinguish sources of P under different soil management practices in a catchment. Brazil is the second largest producer and the largest exporter of tobacco in the world. Inadequate management of cultivated areas exposes the soil to erosion processes, accelerating the transfer of sediment and P to water bodies, which leads to eutrophication. We evaluated the P forms in suspended sediments collected at two rainfall events in the stream of a small catchment in the state of Rio Grande do Sul. The samples were collected upstream and downstream areas in three sub-catchments with different degrees of anthropogenic pressure and in three phases of the hydrograph in the catchment outlet. The first rainfall event occurred during the fallow period, and the second one, during the period of transplanting the tobacco crop. The sediment P forms were evaluated by successive extractions, following the Hedley method. The results showed that an increase in anthropogenic pressure leads to an increase in total inorganic P and a decrease in the levels of organic C and total organic P in sediments. In the control area, the quantity and quality of the eroded material remained the same in both rainfall events. The levels of total P in sediment alone were not sufficient to evaluate the influence of the soil management practices prevalent in each sampling period. However, P fractionation shows that during the tobacco transplanting period, P in sediments was mainly in labile fractions, and rainfall during this period was more likely to promote the eutrophication process. Sediments carried in runoff during the tobacco transplanting period have larger amounts of available P than those borne during rainfall in the fallow period.

Neste trabalho, foram avaliadas as concentrações de fósforo (P) solúvel e nitrato nas águas dos canais de drenagem de uma bacia hidrográfica, com agricultura e produção pecuária intensiva do Sul do Brasil, a fim de avaliar os impactos das atividades agropecuárias no ecossistema aquático. Amostras de água foram coletadas em 11 pontos nos canais de drenagem em três períodos distintos. Coletas diárias, por um período de 30 dias, foram efetuadas no médio curso e no exutório da bacia hidrográfica. As concentrações de nitrato e P solúvel foram maiores nas áreas mais antropizadas e com granjas de suínos próximas a cursos d'água. Nas coletas diárias, observou-se que as concentrações de P mudaram consideravelmente nos dias de chuva, mas a concentração de nitrato manteve certa regularidade durante os períodos com e sem chuva. As altas concentrações de P solúvel e nitrato encontradas foram atribuídas ao manejo inadequado das atividades agropecuárias desenvolvidas na bacia hidrográfica

In order to evaluate the impact of agricultural activities on aquatic ecosystem, the concentration of nitrate and soluble phosphorus (P) in the stream water were assessed in a rural watershed under intensive agriculture and livestock production in southern Brazil. Water samples were collected at 11 points along the drainage system in three different periods. Additionally, daily collections were made during 30 days in the middle and at the outlet of the watershed. Nitrate and soluble P concentrations were higher in the points closer to the more anthropized areas and pig farms. The soluble P concentration changed substantially according to the rainfall events, while nitrate concentration show little change with rainfall regime. The high nitrate and soluble P concentrations were attributed to poor management of the intensive livestock activities undertaken in the watershed

Agricultural activities generate impacts on the environment and require constant study and monitoring to improve understanding of the forms and degree of contamination. The present study aimed to quantify the losses of water, sediment and chemical elements during two rainfall events in two rural watersheds (RW) from an agricultural settlement in Júlio de Castilhos, State of Rio Grande do Sul, Brazil. The studied RWs have an area of 144.5 ha (RW140) and 79.5 ha (RW80), with different land use distribution. The monitored rainfall events occurred in 18 (45.9 mm) and 19 (39.7 mm) September 2012. Water loss by runoff in the RW140 was 5.5%, and in RW80 was 15.2%. In the RW140 the highest concentration of suspended sediment was 1.4 g L-1 compared to 0.9 g L-1 in RW80. The levels of soluble phosphorus in the water samples + sediment in the RW80 ranged between 0.01 and 0.02 mg L-1 and en the RW140 reached 0.06 mg L-1. Total phosphorus in samples of water samples + sediment in the RW140 was higher than the RW80, reaching maximum values of 2.10 and 0.47 mg L-1 in the RW140 in the first and second event, respectively. Both RWs in this study showed low phosphorus losses, moderate losses of bases (Ca, Mg, K e Na) and elements that are constituents of the soil structure as Fe, Al, Mn, and insignificant losses of metallic trace elements.

As atividades agrícolas geram impactos sobre o ambiente e necessitam de constante estudo e monitoramento para melhorar o entendimento das formas e grau de contaminação. O trabalho teve como objetivo quantificar e comparar as perdas de água, sedimento em suspensão e alguns elementos químicos durante dois eventos pluviais sequentes, em duas bacias hidrográficas (BH) rurais situadas no assentamento Alvorada, em Júlio de Castilhos, Rio Grande do Sul, Brasil. As BH’s estudadas possuem 144,5 ha (BH140) e 79,5 ha (BH80), com diferentes proporções de uso do solo. Os eventos pluviométricos ocorreram nos dias 18 (45,9 mm) e 19 (39,7 mm) de setembro de 2012. A perda de água por escoamento superficial na BH140 foi de 5,5% e na BH80 de 15,2%. Na BH140, a máxima concentração de sedimento em suspenção medida foi de 1,4 g l-1 contra 0,9 g l-1 na BH80. O fósforo solúvel nas amostras de água + sedimento na BH80 oscilaram entre 0,01 e 0,02 mg L-1; e na BH140 alcançaram 0,06 mg L-1. O fósforo total das amostras de água + sedimento da BH140 foi superior ao da BH80, alcançando os valores máximos de 2,10 e 0,47 mg L-1 na BH140 no primeiro e segundo evento, respectivamente. As BH’s apresentaram baixa perda de fósforo, perda moderada de bases (Ca, Mg, K e Na) e outros elementos químicos que constituem a estrutura do solo como Fe, Al, Mn e transferência insignificante de elementos traços metálico aos cursos de água

Práticas de manejo que visam reduzir a dependência de fertilizantes inorgânicos, como o uso de dejetos animais como fonte de P, podem contribuir para a sustentabilidade da agricultura. Embora informações sobre a biodisponibilidade e composição química do P presente nos dejetos utilizados como fertilizantes são importantes para o entendimento da sua dinâmica no solo, tais estudos ainda são escassos. Dessa forma, objetivou-se com o este trabalho avaliar o uso do fracionamento químico sequencial, da dessorção com resina de troca e da espectroscopia de ressonância magnética nuclear (31P-NMR) para caracterizar as formas de P presentes em três diferentes dejetos animais (ave, suíno e bovino). O fracionamento químico sequencial do P, a extração sucessiva com resina e a espectroscopia de 31P-RMN demonstraram que as formas de P presentes nos dejetos de aves, bovinos e suínos são principalmente inorgânicas e altamente biodisponíveis. O teor de P orgânico e recalcitrante foi desprezível e altamente dependente da relação Ca:P nos dejetos. Os resultados deste trabalho demonstram que o uso dos três diferentes métodos, quando aplicados conjuntamente, permite a caracterização completa do P presente nos dejetos animais.

Phosphate release kinetics from manures are of global interest because sustainable plant nutrition with phosphate will be a major concern in the future. Although information on the bioavailability and chemical composition of P present in manure used as fertilizer are important to understand its dynamics in the soil, such studies are still scarce. Therefore, P extraction was evaluated in this study by sequential chemical fractionation, desorption with anion-cation exchange resin and 31P nuclear magnetic resonance (31P-NMR) spectroscopy to assess the P forms in three different dry manure types (i.e. poultry, cattle and swine manure). All three methods showed that the P forms in poultry, cattle and swine dry manures are mostly inorganic and highly bioavailable. The estimated P pools showed that organic and recalcitrant P forms were negligible and highly dependent on the Ca:P ratio in manures. The results obtained here showed that the extraction of P with these three different methods allows a better understanding and complete characterization of the P pools present in the manures.

RESUMO Ainda são poucas as informações sobre a influência da luminosidade na produção de biomassa bem como no teor de alguns nutrientes em folhas de Ilex paraguariensis. Este trabalho teve por objetivo avaliar a produção de biomassa da parte aérea da Ilex paraguariensis A. St. Hil. (ramos e folhas) e o teor de nitrogênio, potássio, fósforo, cálcio, magnésio e ferro em folhas produzidas em dois sistemas de cultivos, consorciado com Pinus elliottii Engel. e solteiro, ao longo das estações do ano no município de Frederico Westphalen-RS. Os resultados mostraram que a produção de biomassa da Ilex paraguariensis (folhas + ramos) é maior no cultivo solteiro quando comparada ao consorciado, porém, quando comparados os dois sistemas de cultivo com relação aos teores de fósforo, mas principalmente cálcio, magnésio e ferro, observou-se uma variação pequena para as diferentes épocas do ano, o que indica uma atividade metabólica mais constante da planta de erva-mate sob uma condição mais sombreada, o que torna um importante fator na qualidade final do produto.

ABSTRACT They are still few the information on the influence of the brightness in the production of biomass as well as in the concentration of some nutritious in leaves of Ilex paraguariensis. This work aimed to evaluate the production of dry matter of the aerial part of the Ilex paraguariensis A. St. Hil. (branches and leaves) and the concentration of nitrogen, potassium, magnesium and iron in leaves produced in two systems of cultivations, intercropping with Pinus elliottii Engel. and single, along the seasons in the municipality of Frederico Westphalen, Rio Grande do Sul state. The results showed that the production of biomass of the Ilex paraguariensis (leaves + branches) is larger in the single cultivation when compared to the intercropping. However, when comparing the two cropping systems with respect to phosphorus, but especially calcium and magnesium, there was a small variation for different periods of the year, which indicates a more constant metabolic activity of the plant yerba mate in a more shaded condition, which makes it an important factor in the final quality of the product.

A maioria das pastagens naturais no bioma Campos no sul do Brasil cresce em solos com baixa disponibilidade de fósforo (P), mas com altos teores de P total e de P orgânico. Este trabalho objetivou avaliar as alterações nas formas de P no solo, ao longo de um ciclo de crescimento de pastagens naturais, decorrentes da aplicação de fontes de fosfato. Em três experimentos instalados em áreas de pastagem natural, foi aplicado P nas formas de hiperfosfato de Gafsa, superfosfato triplo e testemunha, arranjados em blocos casualizados com três repetições. Nos experimentos instalados no município de Candiota, RS, em pastagens naturais sob Luvissolo Úmbrico e Neossolo Litólico, foram aplicados 100 kg ha-1 de P2O5 em setembro de 2010. Na pastagem sob Argissolo Vermelho no município de Santa Maria, RS, foram aplicados 180, 90, 100 e 100 kg ha-1 de P2O5 nos anos de 1997, 1998, 2002 e 2010, respectivamente. Amostras de solo foram coletadas (0-10 cm) ao longo da estação de crescimento da pastagem (0, 55, 116, 171 e 232 dias, após aplicação do fosfato em Candiota; e 0, 50, 83, 129, 159 e 186 dias, após aplicação do fosfato em Santa Maria). Foram analisados os teores de P disponível por resina de troca aniônica, o P imobilizado na biomassa microbiana do solo, o P extraído por NaOH 0,1 mol L-1, o P orgânico total e o P total. Os teores de P disponível aumentaram rapidamente com a aplicação de fosfato solúvel, mas no final do período de avaliação esses se equivaleram ao do fosfato natural, que foi semelhante à testemunha. A aplicação de fertilizantes fosfatados sob pastagens naturais com baixa disponibilidade de P aumentou a importância das frações inorgânicas lábeis às plantas, tornando-as menos dependentes da mineralização das frações orgânicas. As frações orgânicas, inclusive o P microbiano, não são bons indicadores da biodisponibilidade de P em pastagens naturais sob Argissolos, Neossolos e Luvissolos do sul do Brasil fertilizadas com fosfatos.

Most natural pastures in the Campos biome in Southern Brazil grow in soils with low phosphorus (P) availability, but with high contents of total and organic P. The present study aimed to evaluate the changes in forms of soil P resulting from the application of phosphate sources over a growth cycle of natural pastures. In three experiments under natural pasture, P was applied in the form of Gafsa rock phosphate, triple superphosphate, and a control treatment in a randomized block design with three replications. In the trials carried out in natural pastures in the municipality of Candiota (RS) in an Alfisol and an Entisol, 100 kg ha-1 of P2O5 was applied in September 2010. In natural pasture in an Ultisol in the municipality of Santa Maria (RS), 180, 90, 100, and 100 kg ha-1 of P2O5 were applied in the years 1997, 1998, 2002, and 2010, respectively. Soil samples were collected (0-10 cm) throughout the natural grassland growing season (0, 55, 116, 171, and 232 days after P application at Candiota and 0, 50, 83, 129, 159, and 186 days after application of phosphate at Santa Maria). The levels of available P were analyzed by anion exchange resin, as well as P immobilized in the soil microbial biomass, P extracted by 0.1 mol L-1 NaOH, total organic P, and total P. The available P content increased rapidly with the application of soluble phosphate, but at the end of the evaluation period it was equivalent to the Gafsa rock phosphate, which was similar to the control. The application of phosphate fertilizers on natural pastures with low P availability increased the importance of the labile inorganic P forms to the plants, making them less dependent on the mineralization of organic P fractions. The organic fractions, including microbial P, are not good indicators of the bioavailability of P in natural pastures under Alfisols, Entisols, and Ultisols in Southern Brazil fertilized with phosphates.

O conhecimento das principais fontes difusas de produção de sedimento pode aumentar a eficiência de utilização dos recursos públicos, investidos em estratégias de gestão em bacias hidrográficas, que visem mitigar a transferência de sedimentos aos cursos d'água. Objetivou-se com este trabalho avaliar as fontes de sedimentos numa bacia hidrográfica rural de cabeceira com predomínio de cultivos anuais sob plantio direto e com intensa e inadequada exploração dos recursos naturais, por meio da quantificação da contribuição relativa das estradas e das lavouras na produção global de sedimentos. A bacia hidrográfica está localizada no município de Júlio de Castilhos, Rio Grande do Sul. O período de estudo foi de maio de 2009 a abril de 2011. Para a identificação das fontes, foi utilizado o método fingerprinting, que compara os solos de diferentes fontes e os sedimentos que são encontrados em suspensão no canal de drenagem, usando elementos traçadores. O manejo inadequado do solo nas áreas de lavoura, a falta de planejamento das vias de acesso e a ausência de práticas de controle do escoamento superficial, que sejam compatíveis com a fragilidade condicionada pelos solos e pelo relevo da bacia hidrográfica, têm provocado o surgimento de processos erosivos acelerados com efeitos negativos ao agricultor e à sociedade. As estradas apresentam alta porcentagem de contribuição na transferência de sedimentos, mas a contribuição das áreas de lavoura aumenta em precipitações pluviais de alta magnitude. Isso evidencia que a magnitude dos eventos de chuva influencia a proporção de contribuição entre as fontes ao longo do ano na bacia hidrográfica, interferindo no processo de mobilização de sedimentos e nutrientes em direção à rede de drenagem.

Knowledge of the main diffuse sources of sediment production can enhance efficiency in use of public resources invested in management strategies that seek to mitigate sediment transfer to waterways from catchment areas. The aim of the present study was to evaluate the sediment sources in a rural catchment with predominance of annual crops under a no-tillage system and with intense and inappropriate exploitation of natural resources (soil and water) by quantifying the relative contribution of roads and croplands in the overall production of sediments. Inappropriate exploitation is a result of a lack of planning of crop production areas and access pathways, both from the point of view of their location in the landscape, and of management practices which are incompatible with the conditions of soil fragility and relief. The catchment is located in the municipality of Julio de Castilhos, State of Rio Grande do Sul. The period under study was from May 2009 to April 2011. For identification of the sources we used the fingerprinting method, which compares the soils from different sources and the sediments in suspension in the drainage canal using tracer elements. Inadequate soil management in croplands, the lack of planning of access roads, and the absence of control practices for surface runoff compatible with the fragility brought about by the soil and topography of the watershed have caused the emergence of accelerated erosion with negative effects for the farmer and society. Roads represent a high percentage of contribution to sediment transfer, but the contribution of cropland increases with rainfall of high magnitude. This shows that the magnitude of rainfall events affects the proportion of contribution among sources throughout the year in the catchment area, affecting the process of mobilization of sediments and nutrients towards the drainage system.

Solos com baixo teor de argila e matéria orgânica apresentam baixa disponibilidade de enxofre (S) e, por isso, as culturas podem responder à adubação sulfatada. No entanto, a mobilidade de S no perfil do solo e sua deposição atmosférica pela água da chuva dificultam o estabelecimento do nível de suficiência do nutriente no solo. Este trabalho objetivou avaliar a resposta de culturas à adubação sulfatada e quantificar o S atmosférico depositado no solo pela água da chuva. Os cultivos avaliados (mamoneira, trigo, feijão-de-porco e milheto) foram realizados entre 2006 e 2009, em um Argissolo Vermelho distrófico arênico. As doses de S aplicadas em cada cultivo foram de 0, 5, 10 e 20 kg ha-1, utilizando-se gesso agrícola como fonte de S. Avaliaram-se a produção de matéria seca e o acúmulo de S na parte aérea do milheto e do feijão-de-porco, e a produção e o teor de S nos grãos de mamona e de trigo. Determinou-se o teor de S disponível no solo até 60 cm de profundidade e a deposição de S pelas precipitações. A maior produção de grãos da mamona e de matéria seca do segundo cultivo de feijão-de-porco foi obtida com aplicação de 14,5±0,35 kg ha-1 de S. Mesmo com teores de S abaixo dos níveis de suficiência, não houve respostas do trigo, do milheto e do primeiro cultivo de feijão-de-porco à adubação sulfatada. O aporte de S atmosférico ao solo foi de 4,5 kg ha-1 ano-1 e pode ter contribuído para a ausência de resposta desses cultivos.

Soils with low levels of clay and organic matter have low sulfur (S) availability. Therefore, crop yields may increase due to S fertilization. However, the mobility of S in the soil profile and its atmospheric deposition by rainwater make it difficult to establish the S sufficiency level in the soil. The objective of this study was to evaluate the response of crops to S fertilization and quantify the S atmospheric deposition in the soil via rainwater. The cultivations evaluated (castor bean, wheat, jack bean and millet) were performed between 2006 and 2009 in a Hapludalf. The S doses applied in each cultivation were 0, 5, 10 and 20 kg ha-1, using gypsum as a S source. The dry matter production and S accumulation were evaluated the in the shoots of millet and jack bean, and production and the S content were evaluated in castor bean and wheat. We also determined the level of available S in the soil to a depth of 60 cm and the S deposition by rainfall. The highest grain yield of castor bean and the highest dry matter yield in the second cultivation of jack bean were obtained with the application of 14.5±0.35 kg ha-1 S. Even with S content below the sufficiency levels, there was no response of wheat, millet and the first crop of jack bean to the S fertilization. The atmospheric input of S to the soil was 4.5 kg ha-1 year-1 and it may have contributed to the no response of these crops.

Tobacco cultivation in shallow soils and steep landscape under intense use of agrochemicals contributes to environment degradation. In this study, we assessed the concentration of agrochemicals in draw wells used for human consumption and a creek in a small catchment predominantly cropped to tobacco. Chlorpyrifos, flumetralin, and iprodione were determined by gas chromatography with electron capture detection, while imidalcloprid, atrazine, simazine, and clomazone were quantified by high-performance liquid chromatography with UV detection. Considering all sampling sites, all agrochemicals were detected at least once, except for flumetralin. The occurrence of agrochemicals in tobacco crops is a consequence of their fast transfer to surface water.

As aplicações sucessivas de dejetos de suínos na superfície do solo podem aumentar o teor de fósforo (P) e alterar a sua adsorção, potencializando a transferência para as águas superficiais ou subsuperficiais. O presente trabalho objetivou avaliar o acúmulo e o potencial contaminante do P em um solo com aplicação de dejetos de suínos. Em março de 2010, após oito anos da instalação de um experimento localizado no município de Braço do Norte, Santa Catarina (SC), sobre um Argissolo Vermelho, foram coletadas amostras de solo nas camadas de 0-2,5; 2,5-5; 5-10; 10-15; 15-20; e 20-30 cm, nos tratamentos sem aplicação de dejeto, com aplicação de dejetos líquidos de suínos e com a aplicação de cama sobreposta de suínos. Nesse período, foram aplicados 694 e 1.890 kg de P2O5 ha-1 nos tratamentos com dejetos líquidos de suínos e cama sobreposta, respectivamente. Determinou-se o teor de P extraído por Mehlich-1, resina trocadora de ânions (RTA), CaCl2 0,01 mol L-1 e o P total no solo coletado, bem como foram determinados os parâmetros das isotermas de adsorção pelos modelos de Langmuir e de Koski-Vähälä & Hartikainem, nas camadas de 0-2,5 e 20-30 cm. A aplicação de 1.890 kg de P2O5 ha-1 na forma de cama sobreposta de suínos promoveu o acúmulo de P extraído por Mehlich-1 até 15 cm de profundidade, de RTA e CaCl2 0,01 mol L-1 até 20 cm e de P total até 30 cm. A adição de 1.890 kg de P2O5 ha-1 na forma de cama sobreposta de suínos provocou os menores valores de capacidade máxima de adsorção de P no solo da camada mais profunda (20-30 cm), indicando a ocupação de parte dos sítios de adsorção das partículas. A adição de cama sobreposta de suínos no solo ao longo de oito anos aumentou a quantidade de P na solução na camada superficial do solo, o que significa risco de contaminação ambiental de águas superficiais e subsuperficiais.

Successive applications of pig litter to the soil surface can increase the phosphorus (P) content and alter its adsorption, promoting P transfer to surface or subsurface waters. The purpose of this study was to evaluate P accumulation and the pollution potential of a soil after application of pig litter. In March 2010, eight years after the installation of an experiment in Braço do Norte, Santa Catarina, SC, Brazil, on a Typic Hapludult, soil was sampled (layers 0-2.5, 2.5-5, 5-10, 10-15, 15-20 and 20-30 cm) after the following fertilization treatments: no pig litter fertilization, pig slurry application and pig manure application. In this period, 694 and 1,890 kg P2O5 ha-1 were applied in the treatments with pig slurry and pig manure, respectively. The P content was determined, based on Mehlich-1, anion exchange resin (AER), 0.01 mol L-1 CaCl2 and total P in the samples. The adsorption isotherm parameters were also determined by the Langmuir and Koski-Vähälä & Hartikainem models in the layers 0-2.5 and 20-30 cm. The application of 1,890 kg P2O5 ha-1 in the form of pig manure led to P accumulation, as evidenced by Mehlich-1, down to a depth of 15 cm, by AER and 0.01 mol L-1 CaCl2 down to 20 cm and by total P to 30 cm. After application of 1,890 kg P2O5 ha-1 in the form of pig manure, the values of maximum P adsorption capacity were lowest in the deepest layer (20-30 cm), indicating the occupation of part of the adsorption sites of the particles. The application of swine manure to the soil over eight years increased the P quantity in the soil solution of the surface layer, indicating environmental contamination risk for surface and subsurface waters.