Abstract Introduction: Iron (Fe) and manganese (Mn) are bioessential micronutrients for plants but can impair the energetic metabolism when present at high levels. Objective: To assess the photosynthetic performance and oxidative damages in Rhizophora mangle L. leaf tissues at low and high concentrations of Fe (74 and 195 mg kg-1; Feleaf) and Mn (65 and 414 mg kg-1; Mnleaf). Methods: Photosynthetic pigments, chlorophyll a fluorescence, leaf CO2 assimilation and gas exchange and DPPH• radical scavenging capacity were sampled in R. mangle growing in estuarine forests in the North region of Espírito Santo State and the extreme South of Bahia State (Brazil) showing low and high Feleaf and Mnleaf. Results: Effects of high Fe and Mn were not identified on pigment levels. The increase in Feleaf and Mnleaf at the levels observed in this assessment had a positive effect on the number of reaction centers and on the efficiency of the oxygen-evolving complex, evaluated as K-band, while no changes were found in the parameters related to the excitation trapping efficiency at the active center of photosystem II. Distinct interference patterns of Fe and Mn on the functional processes of photosynthesis were identified, especially on CO2 assimilation and reactive oxygen species metabolism, with major effects on CO2 assimilation and carboxylation efficiency of Rubisco at high Mnleaf. Conclusion: These findings demonstrate the efficiency of R. mangle in positively regulating the electron transport chain in response to high Fe and Mn, at least in terms of the preservation of structure and functionality of the plant photosynthetic apparatus. Moreover, interference of high Mnleaf in R. mangle occurs at non-stomatal and biochemical levels. There is an antagonistic interference of these trace elements with the physiology of R. mangle, which is a dominant species in Brazilian mangroves.

Resumen Introducción: El hierro (Fe) y el manganeso (Mn) son micronutrientes bioesenciales para las plantas, pero pueden afectar el metabolismo energético cuando están presentes en niveles altos. Objetivo: Evaluar el desempeño fotosintético y los daños oxidativos en tejidos foliares de Rhizophora mangle L. a bajas y altas concentraciones de Fe (74 y 195 mg kg-1; Feleaf) y Mn (65 y 414 mg kg-1; Mnleaf). Métodos: Se muestrearon pigmentos fotosintéticos, fluorescencia de clorofila a, asimilación e intercambio de gases de CO2 foliar y capacidad de eliminación de radicales DPPH• en R. mangle que crece en bosques de estuarios en la región Norte del estado de Espírito Santo y el extremo Sur del Estado de Bahía (Brasil) mostrando Feleaf y Mnleaf bajos y altos. Resultados: No se identificaron efectos de niveles elevados de Fe y Mn en los niveles de pigmento. El aumento de Feleaf y Mnleaf en los niveles observados en esta evaluación tuvo un efecto positivo en el número de centros de reacción y en la eficiencia del complejo generador de oxígeno, evaluado como banda K, mientras que no se encontraron cambios en los parámetros relacionados con la eficiencia de atrapamiento de excitación en el centro activo del fotosistema II. Se identificaron distintos patrones de interferencia de Fe y Mn en los procesos funcionales de la fotosíntesis, especialmente en la asimilación de CO2 y el metabolismo de las especies reactivas de oxígeno, con efectos importantes en la asimilación de CO2 y la eficiencia de carboxilación de Rubisco a niveles altos de Mnleaf. Conclusión: Los hallazgos demuestran la eficiencia de R. mangle en la regulación positiva de la cadena de transporte de electrones en respuesta a los altos niveles de Fe y Mn, al menos en términos de preservación de la estructura y funcionalidad del aparato fotosintético de la planta. Además, la interferencia de Mnleaf alto en R. mangle se presenta a niveles no estomáticos y bioquímicos. Hay interferencia antagónica de estos oligoelementos con la fisiología de R. mangle, que es una especie dominante en los manglares brasileños.

RESUMO A quantificação das emissões destes gases do solo é onerosa, uma vez que requer metodologias e equipamentos específicos. O objetivo deste foi avaliar a modelagem utilizando regressão não linear e redes neurais artificiais para estimar a emissão de CO2 em função do manejo do solo, e de suas propriedades físicas e químicas. A emissão de CO2 foi avaliada em dois diferentes manejos do solo, o plantio direto e o cultivo mínimo. As leituras de fluxo CO2 foram realizadas por meio de uma câmara de sistema fechado automático, determinou-se ainda a temperatura e teor de água do solo, densidade do solo e carbono orgânico total. O modelo de regressão e os modelos de redes neurais artificiais foram ajustados a partir da correlação entre as variáveis medidas nas áreas em que o solo foi manejado com plantio direto e cultivo mínimo, com os dados de emissão de CO2. As redes neurais artificiais são mais precisas na determinação das relações entre a emissão de CO2 e a temperatura, teor de água no solo, densidade do solo e carbono orgânico, quando comparado com os resultados de regressão linear.

ABSTRACT Quantifying soil gas emissions is costly, since it requires specific methodologies and equipment. The objective of this study was to evaluate modeling by nonlinear regression and artificial neural networks (ANN) to estimate CO2 emissions caused by soil managements. CO2 emissions were evaluated in two different soil management systems: no-tillage and minimum tillage. Readings of CO2 flow were carried out by an automated closed system chamber; soil temperature, water content, density, and total organic carbon were also determined. The regression model and the ANN models were adjusted based on the correlation of the variables measured in the areas where the soil was managed with no-tillage and minimum tillage with data of CO2 emission. Artificial neural networks are more accurate to determine correlations between CO2 emissions and soil temperature, water content, density, and organic carbon content than linear regression.

ABSTRACT A comprehensive knowledge about micronutrient dynamics in leaves and bunches of black pepper is needed in order to proper diagnose nutrient needs, and thus facilitate fertilization management. This study aimed to evaluate micronutrient concentration and accumulation in leaves and bunches of black pepper bunches to understand the crop nutritional demand. The experiment was carried out on in a commercial field of Piper nigrum ‘Bragantina’ located in São Mateus, Espírito Santo, Brazil. Composite samples of leaves and bunches were taken periodically during two crop cycles and the concentration of Fe, Zn, Mn, Cu, and B were assessed. The micronutrient accumulation curves behaved linearly and quadratically, reaching the maximum accumulation point during the time of harvesting. Fe, Mn and B were the micronutrients with highest concentration in both bunches and leaves of black pepper. The nutrient concentration in leaf tissues varied seasonally. These results may contribute to a more sustainable agriculture, in which fertilization rates should consider different needs through the crop stage.

ABSTRACT. To diagnose and monitor the nutritional status of commercial crops, reference standards must be established based on chemical analyses of soils and leaf tissues. Therefore, the objective of this study was to establish sufficiency ranges, DRIS standards and leaf nutritional diagnoses for palisade grass pastures in the rainy and dry seasons. Of a total of 105 sampled pastures, the 20 highest-yielding areas were used to establish reference standards. In the other, low-productivity pastures, the nutritional status was diagnosed in both the rainy and dry seasons for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), boron (B), copper (Cu), iron (Fe), nickel (Ni), molybdenum (Mo), and zinc (Zn). A productivity of 15 tons ha-1 year-1 was determined as the threshold to separate high-yielding (> 15 tons ha-1 year-1) pastures from low-productivity pastures (< 15 tons ha-1 year-1). Sufficiency ranges and foliar DRIS standards were established for palisade grass pastures in the rainy and dry seasons, which resulted in the recommendation of region- and season-specific sufficiency ranges and DRIS leaf standards. In the rainy season, in more than 50% of the evaluated pastures, nutritional deficiencies in all nutrients except K, B and Zn were observed, while in the dry season, only N, P, Cu, and Mn were deficient.

ABSTRACT Molybdenum (Mo) availability is strongly affected by soil pH, which determines the dynamics of electrical charges and the adsorption of molybdate. This study evaluated the effects of nitrogen (N) and Mo application on the chemical properties of a Latossolo Amarelo (Oxisol) and in Coffea canephora nutrition and productivity throughout two productive cycles under field conditions. The experiment was conducted from June 2018 to May 2020. The experimental design used was in randomized blocks, in a 2 × 5 factorial scheme, the first factor being the absence and presence (4 kg ha-1 yr-1) of molybdic fertilization and the second factor was the N dose (300, 500, 700, 900, and 1,100 kg ha-1 yr-1). At the end of each production cycle, soil samples were collected to evaluate the pH(H2O), pH(KCl), exchangeable aluminum, potential acidity, organic matter, and Mo, at layers of 0.00-0.20 and 0.20-0.40 m. Leaves were sampled from the coffee tree to determine Mo and N contents and the coffee beans were harvested to evaluate the yield of processed coffee. The results showed that urea has a high potential for soil acidification, influencing the values of exchangeable aluminum, potential acidity, and ∆pH, at layers of 0.00-0.20 and 0.20-0.40 m. The decrease in pH caused by increasing doses of N increased the density of positive electrical charges of the soil and reduced Mo content in the leaves of C. canephora by 67 %. The application of sodium molybdate via soil was efficient in providing Mo to Conilon coffee and provided a 3.7 % increase in the yield of processed coffee. Nevertheless, molybdic fertilization did not influence the Mo content in the soil in the evaluations carried out at the end of each production cycle.

RESUMO Informações obtidas a partir de estudos de variabilidade espacial e do Sistema Integrado de Diagnose e Recomendação (DRIS) poderão contribuir para o melhor entendimento da relação entre o balanço de nutrientes e os fatores que limitam a produtividade das culturas. Este estudo mostra que plantas equilibradas nutricionalmente podem estar associadas à baixa produtividade em café Conilon (Coffea canephora). O estudo foi realizado em uma lavoura altamente produtiva de café Conilon em São Mateus, ES. Foi estabelecida uma grade amostral com 100 pontos, cada ponto relacionado a uma planta. Vinte pares de folhas de cada planta foram coletados de ramos produtivos compondo uma amostra para análise nutricional. A incidência da ferrugem (Hemileia vastatrix), a presença da broca do café (Hypothenemus hampei), e características físicas do solo também foram coletadas para cada planta amostrada. O DRIS e o Índice de Equilíbrio dos Nutrientes (IEN) foram calculados e, com os dados de produtividade, foram caracterizados utilizando estatística descritiva. Foram criados mapas com a distribuição espacial do IEN, produtividade, areia total e incidência de ferrugem e da broca do cafeeiro. Verificou-se baixa relação entre equilíbrio nutricional e produção no café Conilon, sugerindo que fatores não nutricionais também influenciaram na produtividade das plantas. Nas áreas dos mapas com alto IEN, o balanço nutricional da planta foi o principal fator limitante da produção, pois a maioria das plantas nessa área produziu menos que a produtividade média das plantas amostradas. O uso de uma ferramenta geoestatística combinada com o IEN resultou em melhor compreensão da relação entre variáveis nutricionais e não nutricionais sobre a produtividade de café Conilon.

ABSTRACT Information obtained from studies of spatial variability and the Diagnosis and Recommendation Integrated System (DRIS) may contribute to understanding better the relationship between mineral nutrient balance and factors that limit the crop yield. This study shows that nutritionally balanced plants may be associated with low productivity in Conilon coffee fields. The study was carried out on a highly productive Conilon coffee (Coffea canephora) field, in São Mateus, state of Espírito Santo, Brazil. A sample grid was established with 100 points, each point linked to one plant. Twenty pairs of leaves from each plant were collected from productive branches to create a sample for nutritional analysis. The rust incidence (Hemileia vastatrix), the presence of the coffee borer (Hypothenemus hampei), and the physical characteristics of the soil were evaluated in each sampled plant. DRIS and Nutrient Balance Index (NBI) were calculated, and from the yield data, they were characterized using descriptive statistics. Maps were created showing the spatial distribution of the NBI, yield, total sand, and incidence of rust and coffee borer. It was verified the low relationship between nutritional balance and yield in Conilon coffee, suggesting that non-nutritional factors also influenced plant production. In areas of the maps with high NBI, the plant’s nutritional balance was the main limiting factor of production, since most plants in this area produced less than the average productivity of the plants sampled. The use of a geostatistics tool combined with the NBI resulted in better understanding of the relationship between nutritional and non-nutritional variables on the Conilon coffee yield.

RESUMO A fertilidade do solo é um fator decisivo para o rendimento das culturas agrícolas e a sua distribuição e correlação espacial, e podem alterar significativamente a produtividade média em uma área cultivada. Objetivou-se no presente trabalho estudar a variabilidade e correlação espacial dos micronutrientes ferro (Fe), cobre (Cu), manganês (Mn), zinco (Zn), da matéria orgânica (MO) e da produtividade em uma área cultivada com macadâmia. O estudo foi desenvolvido em um Latossolo Amarelo distrocoeso, cultivado há 20 anos com macadâmia no município de São Mateus, ES. A malha instalada foi de 144 x 140 m com 100 pontos e com distância mínima de 5 m, onde foi coletada uma amostra composta de solo na profundidade de 0-0,20 m, utilizada para análise química do Fe, Cu, Mn, Zn e da MO. A colheita da macadâmia foi realizada no período de fevereiro a junho de 2015, colhendo-se os frutos na projeção da copa da planta. Os dados foram submetidos à análise geoestatística através do ajuste de semivariogramas experimentais e o método de krigagem foi aplicado para mapear os padrões espaciais dos nutrientes e da produtividade. Todos os atributos em estudo apresentaram estrutura de dependência espacial (forte e moderada). A MO teve correlação positiva com os micronutrientes, e somente o Zn teve correlação positiva com a produtividade. Zn e Mn obtiveram semivariogramas cruzados que explicaram os mapas observados, enquanto o Fe obteve tendência contrária à produtividade da macadâmia.

ABSTRACT Soil fertility is the key to agricultural production. The spatial correlation and location of nutrients may significantly affect the yields. The objective of this work was to evaluate the variability and spatial correlation of iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), and organic matter (OM) with macadamia nut yield. The study was conducted in an Oxisol cultivated for 20 years with macadamia nut in São Mateus, state of Espírito Santo, Brazil. A 100 point grid was used comprising an area of 144 × 140 m with a minimum distance between points of 5 m, in which a single composite soil sample was collected from 0-0.20 m layer for chemical analysis of Fe, Cu, Mn, Zn and OM. Nuts under the canopy’s projection were harvested from February to June, 2015. The data were evaluated by geostatistical analysis using semivariograms, and kriging was used to map spatial distributions of nutrients and nut yield. All evaluated attributes showed strong or moderate spatial dependence structure. The OM was correlated positively with micronutrients, but only Zn was positively correlated with nut yield. Crossed semivariograms adequately explained the maps of Zn and Mn; and Fe showed opposite tendency for macadamia nut yield.

Resumo: O objetivo deste trabalho foi avaliar o sistema radicular de plantas de café conilon (Coffea canephora) e café arábica (Coffea arabica) no perfil do solo, com uso de semivariogramas. As avaliações foram realizadas em área localizada no município de Jaguaré, no estado do Espírito Santo. Foram avaliadas as cultivares Verdebrás G30/G35 do café conilon e a Catuaí Vermelho IAC 44 do café arábica. Monólitos de solo com raízes de café foram coletados em três distâncias do tronco do cafeeiro, no sentido da linha, e em seis distâncias do tronco, no sentido da entrelinha de plantio, em seis níveis de profundidade. As raízes foram coletadas e lavadas e, depois, digitalizadas e processadas no programa Safira. A variabilidade espacial dos atributos avaliados foi caracterizada pela técnica geoestatística, por meio de semivariogramas, com uso do programa GS+ 7.0. A área de superfície, o comprimento e o volume das raízes foram quantificados para as duas espécies de café. O café conilon tem tendência de apresentar sistema radicular com menor área superficial, comprimento e volume de raízes por volume de solo, bem como com distribuição menos discrepante na superfície do solo e em profundidade, em comparação ao café arábica.

Abstract: The objective of this work was to evaluate the root system of Conilon coffee (Coffea canephora) and Arabica coffee (Coffea arabica) plants in the soil profile, using semivariograms. The evaluations were carried out in an area located in the municipality of Jaguaré, in the state of Espírito Santo, Brazil. The Verdebrás G30/G35 Conilon coffee and the Catuaí Vermelho IAC 44 Arabica coffee cultivars were assessed. Soil monoliths with coffee plant roots were collected at three distances from the trunk in the planting row and at six distances from the trunk between rows, at six depths. The roots were collected and washed and then digitized and processed in the Safira software. The spatial variability of the evaluated attributes was characterized by the geostatistical technique, through semivariograms, using the GS+ 7.0 software. Root surface area, length, and volume were quantified for the two coffee species. Conilon coffee plants have a tendency of showing a root system with a smaller surface area, shorter length, and lower volume by volume of soil, as well as a less discrepant distribution on soil surface and in deeper layers, compared with Arabica coffee.

Resumo: O objetivo deste trabalho foi determinar a dinâmica de macronutrientes em folhas e cachos de pimenta-do-reino (Piper nigrum), ao longo dos ciclos reprodutivos da planta. O experimento foi realizado em uma lavoura comercial de pimenta-do-reino 'Bragantina'. Folhas e cachos foram amostrados a cada 21 dias, por um ano, durante dois ciclos de cultivo. Os cachos foram amostrados desde o vigésimo oitavo dia após o lançamento das inflorescências até a maturação completa dos frutos. As amostras de folhas e cachos foram secas, e os conteúdos de N, P, K, Ca, Mg e S foram determinados. N, K e Ca foram os macronutrientes mais comuns nos cachos e nas folhas de pimenta-do-reino. O acúmulo de matéria seca nos cachos de pimenta-do-reino foi similar nos dois ciclos e foi ajustado aos modelos linear e quadrático. O acúmulo e o conteúdo de macronutrientes seguiram a tendência de comportamento da matéria seca. O conteúdo de macronutrientes nas folhas oscila durante o ano, e K e Mg variam mais do que N, P, Ca e S. O conteúdo de macronutrientes em folhas e cachos de pimenta-do-reino depende do estádio vegetativo da planta, e essa variação deve ser considerada no planejamento do manejo de adubação.

Abstract: The objective of this work was to determine the macronutrient dynamics in leaves and bunches of black pepper (Piper nigrum) throughout the plant reproductive cycles. The experiment was carried out in a commercial field of 'Bragantina' black pepper. Leaves and bunches were sampled every 21 days for one year, during two crop cycles. The bunches were sampled from the twenty eighth day after the appearance of inflorescences until the complete fruit maturation. Samples of leaves and bunches were dried, and the contents of N, P, K, Ca, Mg, and S were determined. N, K, and Ca were the most common macronutrients found in the bunches and leaves of black pepper. The accumulation of dry matter in the bunches was similar for both cycles and it was adjusted to the linear and quadratic models. The accumulation and content of macronutrients followed the dry matter behavior trend. Macronutrient contents in leaves oscillate during the year, and K and Mg vary more than N, P, Ca, and S. The macronutrient contents in black pepper leaves and bunches depends on the plant vegetative stage, and this variation should be considered in the planning of the fertilization management.

RESUMO: O objetivo deste trabalho foi estabelecer padrões de solo e padrões foliares para culturas clonais de cacau CCN51 e PS1319 nas regiões do Atlântico no norte do Espírito Santo e no sul da Bahia. As amostras foram coletadas de setembro a outubro de 2015, em 45 parcelas de alta produtividade, sendo 23 parcelas do clone CCN51 e 22 do clone PS1319. As faixas de suficiência para solo e padrões foliares foram sugeridas para os clones de cacau CCN51 e PS1319 plantados no norte do Espírito Santo e no sul da Bahia. Diferenças nos teores dos macronutrientes foliares K, Ca, Mg, S e micronutrientes Fe e Mn foram verificadas entre os clones CCN51 e PS1319. As diferenças relatadas para padrões de diferentes regiões geográficas permitem confirmar que esses padrões precisam ser regionais e específicos para diferentes clones de cacau.

ABSTRACT: The objective of this research was to establish soil patterns and foliar standards for clonal crops of cocoa CCN51 and PS1319 in the Atlantic regions within the northern Espírito Santo and southern Bahia States. Samples were collected from September to October 2015, in 45 high productive plots, being 23 plots of clone CCN51 and 22 of clone PS1319. Sufficiency ranges for soil and foliar standards were recommended for cocoa clones CCN51 and PS1319 planted in the Northern Espírito Santo and Southern Bahia states. Differences in the contents of foliar macronutrients K, Ca, Mg, S and micronutrients Fe and Mn, were verified between clones CCN51 and PS1319. Differences reported for standards from different geographical regions confirmed that these standards need to be regional and specific for different cocoa clones.

The sugarcane is one of the main crops produced in Brazil and is cultivated since the colonial Brazil Times. Soil management in the culture of sugarcane has undergone changes over time, applying new techniques of management and conservation of soil, taking advantage of systematic way the waste from the manufacture of alcohol and sugar, minimizing damage to environment. This aimed to evaluate the chemical attributes of the soil cultivated with sugarcane certified organic with and without soil disturbance, organic certification, conventional with and without straw burning and a remaining area of Cerrado in Goiatuba, Goiás, Brazil. Soil samples were collected in September 2009 in the depths of 0-10 cm and 10-20 cm for chemical analysis. The results were analyzed descriptively by estimating the mean, standard error of the mean and also by means of multivariate analysis, estimating the Euclidean average distance between the treatments with complete connection. There forming groups among the organic cultivation without soil disturbance and the remaining area of Cerrado in the depth 0-10 cm indicating proximity between the evaluated attributes. The organic cultivation without soil disturbance presents phosphorus and potassium far superior to other managements. The results underscore the importance of greater supply of organic waste for improved chemical attributes and maintenance of soil quality

La caña de azúcar es uno de los principales cultivos producidos en Brasil, desde los tiempos coloniales. La gestión del suelo en el cultivo de la caña ha sufrido cambios en el tiempo, con la aplicación de nuevas técnicas aprovechando sistemáticamente los residuos procedentes de la fabricación de alcohol y azúcar, minimizando el daño al medio ambiente. Por lo tanto, el objetivo del presente trabajo fue evaluar las propiedades químicas del suelo cultivado con caña de azúcar orgánica certificada con y sin alteración del suelo, en certificación orgánica, convencional con y sin quema de residuos agrícolas y un área del Cerrado nativo en Goiatuba, Goiás. Las muestras de suelo se recogieron en septiembre de 2009 en las profundidades de 0-10 cm y 10-20 cm para el análisis químico. Los resultados se analizaron de manera descriptiva, mediante la estimación de la media, el error estándar de la media y también por medio del análisis multivariado con estimación de la distancia media euclidiana entre los tratamientos con conexión completa. Hay grupos de formación entre el cultivo orgánico sin la perturbación del suelo y el área de Cerrado nativo en la profundidad de 0-10 cm, lo que indica la proximidad de los atributos evaluados. El cultivo orgánico sin la perturbación del suelo tiene fósforo y potasio superiores a otras gestiones. Los resultados resaltan la importancia de aumentar la oferta de los residuos orgánicos para la mejora de atributos químicos y mantenimiento de la calidad del suelo

The extraction of nutrients from the soil by plants depends on soil fertility, plant management and plant production. The objec-tive of this study was to evaluate the effect of the application of sources and doses of nitrogen on macronutrient extraction by Panicum maximum cv. Mombaga. The experiment was conducted from 1 October 2011 to 14 April 2012 in the Federal Institute of Espirito Santo, Santa Teresa Campus. The experimental design was a randomised block design with three repetitions in a 3 X 6 factorial scheme, with three nitrogen fertilisers (urea, ammonium sulphate and calcium nitrate) and six nitrogen doses (0, 120, 240, 360, 480 and 600 kg ha-1). The established nitrogen doses were divided equally and applied every 28 days after the mombaga grass was cut, resulting in a total of seven applications during the 196-day experimental period. It was observed than nutrient extraction depends on forage plant production and was highest with the higher doses of nitrogen because of the greater dry matter production. The application of high doses of nitrogen in the form of calcium nitrate caused a reduced absorption of magnesium. Nitrogen fertilisation in pastures should be accompanied by the management of other nutrients to avoid nutritional imbalances or the depletion of soil fertility.

ABSTRACT Establishing the number of samples required to determine values of soil physical properties ultimately results in optimization of labor and allows better representation of such attributes. The objective of this study was to analyze the spatial variability of soil physical properties in a Conilon coffee field and propose a soil sampling method better attuned to conditions of the management system. The experiment was performed in a Conilon coffee field in Espírito Santo state, Brazil, under a 3.0 × 2.0 × 1.0 m (4,000 plants ha-1) double spacing design. An irregular grid, with dimensions of 107 × 95.7 m and 65 sampling points, was set up. Soil samples were collected from the 0.00-0.20 m depth from each sampling point. Data were analyzed under descriptive statistical and geostatistical methods. Using statistical parameters, the adequate number of samples for analyzing the attributes under study was established, which ranged from 1 to 11 sampling points. With the exception of particle density, all soil physical properties showed a spatial dependence structure best fitted to the spherical model. Establishment of the number of samples and spatial variability for the physical properties of soils may be useful in developing sampling strategies that minimize costs for farmers within a tolerable and predictable level of error.

RESUMO Objetivou-se, no presente estudo, caracterizar a variabilidade espacial dos atributos relacionados à acidez do solo, a necessidade de calagem e a produtividade de pimenta-do-reino sob um Latossolo Amarelo. O estudo foi realizado em uma lavoura de pimenta-do-reino, no município de São Mateus, ES. A área experimental possui dimensões de 100 x 120 m na qual demarcou-se uma malha com 126 pontos. Em cada ponto amostral foram coletadas três subamostras de solo na projeção da copa da pimenteira-do-reino compondo uma amostra na profundidade de 0-0,20 m. A produtividade da lavoura foi estimada por meio da colheita das três plantas circunvizinhas a cada ponto amostral. Os resultados obtidos foram submetidos à análise da estatística descritiva e à análise geoestatística. O mapa da necessidade de calagem possibilitou a delimitação das zonas homogêneas de taxas de calcário a serem aplicadas ao solo. Os modelos matemáticos ajustados aos semivariogramas demonstraram que todas as variáveis em estudo apresentaram estrutura de dependência espacial. O conhecimento da variabilidade espacial associada à definição de zonas homogêneas pode ser usado para aumentar a eficiência de aplicação de calcário.

ABSTRACT Studies aimed at determining homogeneous zones and the spatial variability of soil characteristics may improve the efficiency of agricultural input applications. The purpose of this study was to determine homogeneous zones for liming applications and to characterize the spatial variability of characteristics related to soil acidity and productivity in an Oxisol cultivated with black pepper (Piper nigrum L.). This study was carried out in São Mateus, state of Espírito Santo, Brazil. The experimental site was 100 x 120 m. A grid with 126 sampling points was established. Three soil sub-samples were collected at each sampling point in the black pepper canopy areas, at a 0-0.20 m depth. Crop productivity was estimated by harvesting the three plants neighboring each sampling point. Descriptive statistics and geostatistical analyses were performed. Homogeneous management zones were defined based on map of liming needs. Mathematical models adjusted to semivariograms indicated that all of the studied variables exhibited spatial dependency. An analysis of the spatial variability together with the definition of homogeneous zones can be used to increase the efficiency of soil liming.

Resumo: O objetivo deste trabalho foi avaliar a distribuição do sistema radicular do cafeeiro conilon (Coffea canephora) irrigado e não irrigado. Utilizaram-se plantas de conilon da variedade clonal Emcapa 8111, genótipo 02, com cinco anos de idade. Utilizou-se o delineamento inteiramente casualizado, em parcela subsubdividida, com cinco repetições. Os tratamentos consistiram de: presença e ausência de irrigação (parcelas), 13 distâncias do tronco (dez no sentido da entrelinha e três no sentido da linha de plantio) e seis camadas de solo (0-60 cm) nas subparcelas. As raízes foram coletadas, lavadas, digitalizadas e processadas pelo programa Safira, para quantificar área superficial, comprimento, volume e diâmetro. As plantas de conilon não irrigadas apresentaram maiores área superficial, comprimento e volume de raízes por volume de solo, bem como distribuição de raízes menos discrepante na superfície do solo e em profundidade, em comparação às plantas irrigadas. O sistema de irrigação por gotejamento promove maior distribuição de raízes nas plantas irrigadas, na zona compreendida pelo bulbo úmido da irrigação.

Abstract: The objective of this work was to evaluate the distribution of the root system of irrigated and nonirrigated conilon coffee (Coffea canephora). Conilon plants of the clonal variety Emcapa 8111, genotype 02, with five years of age, were used. The design was completely randomized in split-split plots with five replicates. The treatments consisted of: presence and absence of irrigation (plots), 13 distances from the stem (ten in the direction between rows and three of the planting row) and six soil layers (0-60 cm) in the split-plots. Roots were collected, washed, scanned, and processed by the Safira software to quantify surface area, length, volume, and diameter. Nonirrigated conilon plants showed greater root surface area, length, and volume per soil volume, as well as less discrepant distribution of roots in the soil surface and in depth, in comparison to irrigated plants. The drip irrigation system promotes higher root distribution in irrigated plants, in the area covered by the wet-bulb irrigation.