Raimundo Nonato de Assis Júnior

Amostragem e variabilidade espacial de atributos físicos de um latossolo vermelho em Mossoró, RN

The soils, some those considered homogenous, show some spatial and temporal variability of its physical, chemical and biological atributes. To define this variability is very important to efficient soil management. This study had the objective of investigating the spatial variability of some physical attributes of an Red Latosol in Mossoro, state of Rio Grande do Norte, Brazil, to determine the best procedure for soil sampling. Soil samples were collected on a 100 x 100 m area, in 10 m grid marking, from the 0-0.2 m soil layer, totaling 100 samples. The following soil attributes were analyzed: particle size, bulk density, particle density, total porosity, and water retention at tensions of 0.033 and 1,500 MPa. The data were analyzed through descriptive statistics and geostatistics. Results indicated that soil variability, measured by the coefficient of variation, was low for sand, bulk density, particle density and total porosity and intermediary for silt, clay, field capacity, and permanent wilting point. The distribution frequency for most analyzed variables was normal, with exception of sand, bulk density and total porosity. The mapping of the studied variables suggested that the establishment of homogeneous subareas would make the natural resources management, especially of water, more effective.

Análise espacial de atributos físicos e carbono orgânico em argissolo vermelho-amarelo cultivado com cana-de-açúcar

A agricultura convencional utiliza o solo intensivamente, modificando os seus atributos. Neste estudo, objetivou-se avaliar a variabilidade espacial de alguns atributos fisicos e carbono orgânico do solo em um Argissolo Vermelho-Amarelo cultivado com cana-de-acucar, usando geoestatistica. O trabalho foi realizado em Maracanau - CE, em uma area de producao de cana-de-acucar, manejado mediante preparo conservacionista sobre uma cobertura de palhada de cana-de-acucar. As amostras de solo foram retiradas de uma profundidade de 0,00 - 0,20 m, em uma malha, com intervalo regular de 10 m, totalizando 100 pontos. Em cada amostra, foi analisado densidade de particulas, densidade do solo, carbono orgânico, porosidade total, macroposidade e microposidade. O coeficiente de variacao indicou variabilidade baixa para densidade de particulas, densidade do solo e porosidade total e media para as variaveis macroporosidade, microporosidade e carbono orgânico. As variaveis analisadas mostraram dependencia espacial, a qual foi observada nos mapas de krigagem. A distribuicao de poros por tamanho e a porosidade total indicam condicoes fisicas razoavelmente boas, embora com valores de densidade do solo ligeiramente acima do nivel considerado adequado para a classe textural do solo.

Atributos mineralógicos de três solos explorados com a cultura do melão na Chapada do Apodi: RN

The present study aimed at characterizing the main soil types under melon crop in the Apodi Tableland, state of Rio Grande do Norte. This investigation focused on the mineralogical soil features as an attempt to generate information for adequate soil and crop management. Three soil types were selected: Typic Haplocambids, Typic Eutrotorrox and Arenic Kandiustults. The mineralogy of sand, silt and clay fractions was evaluated through X ray diffraction analyses and scanning electron microscopy in complementary, undisturbed samples. The mineralogical composition was similar in the studied profiles; quartz prevailed in the sand and silt fractions, while the clay fraction consisted predominantly of kaolinite. Profile 1 (CXve), compared with the other two profiles, was the least developed according to the pedogenetic scale. The degree of profile development was almost the same in the profiles 2 (LVAe) and 3 (PVd), although profile 2 was slightly more developed. The fact that profile 1 (CXve) showed chemical properties of a very young soil in contrast with the mineralogy of a well developed soil, demonstrates an incoherence between the two soil attributes and the stage of soil development. Considering the semi-arid conditions of the sites from where the soil samples were collected, the predominance of kaolinite in the clay fraction suggestes that the soils had been formed under climatic conditions distinct than the present. Former conditions were probably more humid, or the soils developed from pre-weathered parent material.

Variabilidade espacial das frações primárias e agregados de um Argissolo no estado do Ceará

The spatial variability has been one of the concerns of researchers since the beginning of the century, being the soil management system a factor that interferes in the spatial distribution of the physical properties of the soil. The objective of this research was to characterize and determine the spatial variability of physical attributes of an Alfisols, by using geostatistical methods and surface maps using the Kriging interpolation method, at two soil depths. Soil sampling was performed following a 2.5 x 2.5 regular grid, in an area of 400 m2, with a total of 81 points in each one of the soil depths (0-0.2 m and 0.2-0.4 m). The 162 samples were subjected to the physical analysis and the data was tested for normality using descriptive statistics and later submitted to the geostatistical analysis. The spherical semivariogram model was the best fitting, for most of the variables. Random variance was verified for the variables flocculation degree, at the 0-0.2 m depth and aggregate stability at the 0.2-0.4 m depth.

Spatial variability of an Alfisol cultivated with sugarcane

La variabilidad del suelo ocurre debido a factores que actuan en varias escalas espaciales y temporales, naturales o antropicas. El objetivo del presente estudio fue evaluar la variabilidad espacial y la relacion de algunos atributos quimicos, mediante diferentes tecnicas estadisticas. El trabajo fue realizado en el municipio de Maracanau (CE, Brasil), en area comercial de cana de azucar, en un Typic Hapludalfs. Se tomaron muestras de suelo cada 10 m, en una malla regular de 100 m x 100 m, en una capa entre 0 y 0,20 m, para la determinacion de acidez intercambiable, pH (KCl), Ca, Na, K, Mg, P, N, suma de bases, capacidad de intercambio cationica, saturacion de bases y materia organica. Los datos fueron analizados mediante estadistica descriptiva, multivariada y, geoestadistica e interpolacion por kriging ordinario. Los atributos presentaron variabilidad baja o media, donde el pH fue el unico atributo que no presento dependencia espacial. Las diferentes tecnicas estadisticas ayudaron a caracterizar la variabilidad espacial del suelo y la identificacion de las diferentes relaciones entre atributos, cuyos resultados permiten una mejor planeacion y control en la produccion agricola, especialmente en la realizacion de practicas de manejo localizado de insumos agricolas.

Contribuição de material amorfo na gênese de horizontes coesos em Argissolos dos Tabuleiros Costeiros do Ceará

The coastal plains, in the North, Northeast and Southeast Brazil, soils with cohesive layer are common, and can cause physical impediment to root and water. However, the genesis of these horizons is still unknown. The main objective of this work was to evaluate the influence of amorphous materials on the cohesion processes with cohesive layers from a toposequence in Trairi - CE. Four soil profiles were described and characterized (physically and chemically). Three soils present cohesive layers (P2, P3 and P4) and one (P1) did not. To evaluate the effect of amorphous material in the cohesion, samples of Bt1 horizons were subjected to two treatments: with and without extraction of amorphous material. Samples (with and without extraction) were subjected to three cycles of wetting and drying and then the penetration resistance (PR) was determined. Based on the chemical and physical analysis, the soils were classified as Ultisols. The highest expression of the cohesive character was found in P4, located in the lowest position of the landscape, suggesting the influence of relief on the intensification of the cohesion. Despite the low clay content and the loosening of the soil, a high PR was achieved after only a few cycles of wetting and drying. After extraction of amorphous material, the cohesive horizons of profiles P2 and P4 showed a significant reduction of PR, indicating that these compounds act in the genesis of cohesive layers.

Qualidade física de um cambissolo sob sistemas de manejo

The Apodi Tableland is becoming known as a promising center of irrigated fruit production because of the agricultural potential of its soils. The physical properties of these soils are modified by different management types. The purpose of this study was to evaluate the physical properties of an Inceptisol under papaya (Carica papaya L.) in two tillage systems, compared to the same soil type under secondary forest. Samples of disturbed and undisturbed soil were collected for analysis of texture, clay dispersed in water, bulk density, particle density, aggregate stability, organic carbon, and penetration resistance. The clay flocculation degree and organic matter content were calculated. The soil hydraulic conductivity was tested in the field. The 3 x 3 x 5 factorial scheme consisted of two soil management systems (papaya planted in furrow and ridge) and native secondary forest; three soil layers (0-0.1; 0.1-0.2, and 0.2-0.3 m), in five replications, except for the hydraulic conductivity, for which a factorial 3 x 2 x 5 (two soil management systems and secondary forest; two tensions - 0 and 5 hPa; five replications) was used, in a completely randomized design. The Kolmorogov-Smirnov Test was used to verify the normality of data distribution, the F Test for analysis of variance and Tukeys test for mean comparison, all at p=0.05. It was concluded that: a) the hypothesis that the tillage systems worsen the physical soil quality was refuted, indicating that the quality of the cultivated soil was generally maintained or improved in relation to the status of the native soil; b) the decrease of the organic matter content, percentage of stable aggregates (diameter class 4.76-2.00 mm) and the mean weighted diameter in cultivated soil, although still far from critical limits, indicate the need for management practices that avoid soil degradation; c) the soil quality indices were sensitive to changes caused by soil management systems and can therefore be used as a basis of interpretation of the dynamics of soil physical processes in time.

Efeito da qualidade da água de irrigação sobre os atributos físicos de um neossolo flúvico do Município de Quixeré, CE - Brasil

The water quality used in irrigation is a decisive factor for crop productivity and soil quality in the Brazilian semiarid. The effects of the saline concentrations of two different water quality samples (river and shallow well resources) on the physical properties (clay dispersed in water, flocculation level, density, porosity, stability and mean weighted diameter of water-stable aggregates) were tested. The experiments were carried out in 2000/2001 on an Entisol under Musa sp. cv. Pacovan. The soil density, water-dispersed clay, and the flocculation level were sensitive to increments of salts in the well-irrigated treatment. The contraction and expansion of the studied soil possibly influenced the macroporosity and aggregate stability variations, since the saline concentrations from both sources were not high enough to alter these two physical properties. The effects of salts on the flocculation and dispersion processes may have been reduced or masked by the short time during which the soil was exposed to the salinization agents.

Rede de poros de um Cambissolo sob diferentes usos e índice S relativizado como indicador da qualidade física do solo

The objective of this work was to evaluate soil porous media quality under different uses, as well as to propose a new index to monitor changes in its structure due to management: the Srelative index. An Inceptisol under irrigated banana cultivation and secondary forest, in the Brazilian Apodi Plateau, was evaluated at three soil layers (0.0–0.1, 0.1–0.2, and 0.2–0.3 m) as to: particle size, particle and bulk density, organic matter content, intrinsic permeability to air, and water retention curve. Total porosity, index for pore continuity (defined by the ratio between soil intrinsic permeability to air and aeration porosity), volume of blocked pores, and the S and Srelative indices were determined. The Srelative index was calculated as the ratio between S-index values from undisturbed and disturbed samples of the same soil (Sundisturbed/Sdisturbed). Under the studied conditions, the Srelative index is a good quantifier of the changes imposed by soil use and management. Soil cultivation maintains or improves the quality of the evaluated attributes, except for blocked porosity, when compared with the soil under native secondary forest with ten years of regeneration after agricultural use.

EFEITO DA RESSATURAÇÃO DA AMOSTRA SOBRE A CURVA CARACTERÍSTICA DE ÁGUA NO SOLO

Soil-water characteristic curve (SWCC) is an important tool for water management in irrigated agriculture. However, factors such as texture and structure of soils influence SWCC behavior. According to the literature, wetting and drying cycles alter SWCC. A similar process of re-saturation and drying occurs during SWCC obtainment under laboratory conditions. Based on the hypothesis that re-saturation process alters SWCC due to clay loss in the sample, this study aimed to obtain the SWCC, S index, and pore size distribution from samples submitted to re-saturation cycles, as well as from not re-saturated samples but under higher matric potentials (−2, −4, −6, −8, and −10 kPa). For this, disturbed and undisturbed soil samples, collected from the A (sandy texture) and Btg (sandy clay loam texture) horizons of a Argissolo Acizentado, were used. After obtaining SWCC, each air-dried soil sample was submitted to particle size and clay dispersed in water analyses to verify whether the soil lost clay. The experimental design was a completely randomized design with two methods of SWCC constructing (with and without re-saturation) and eight replications. The re-saturation process generates a loss of clay in the sample, not causing significant changes in SWCC considering the assessed textural soil classes. In addition, sandy soil samples are more sensitive to changes in pore size distribution when submitted to re-saturation.