Different soil managements evidence soil properties, contributing positively or negatively to its quality. A study was conducted in the city of Martins, Rio Grande do Norte (RN) state, in four cultivated areas: corn intercropped with beans (CICB), cassava monocrop (CAMO), bean monocrop (BEMO) and native forest (NF, considered as the original soil condition). This study aimed to evaluate changes in the chemical properties of an Oxisol in function of different agricultural uses (N, P, K+, Ca2+, Mg2+, Na1+, Al3+, pH, EC, H+Al, BS, V, CEC, t, m, OM and ESP) and the distinction of environments using multivariate analysis. The sampling was performed up to 30 cm deep. Soil pH values were kept close to 5.5, except for the area with corn intercropped with beans, whose values were higher than 7.0. Corn intercropped with beans had the highest concentrations of K+, Na+ and Ca2+ on the soil, with a direct impact on base sum. Different uses modified soil chemical properties. Corn intercropped with beans differs from the other treatments due to the addition of solid waste to the soil. Principal component analyses showed pH and exchangeable bases are the most sensitive indicators of environment separation.

Mineralogical studies are incipient and necessary in the Apodi Plateau, Brazil. This study aimed to evaluate the interrelationship between the mineralogy of the clay fraction and its structural and chemical attributes and to differentiate two important pedo-environments in the semi-arid region of northeastern Brazil (Ferralsol and Cambisols of the Apodi Plateau-RN) using the multivariate technique. We evaluated the interrelationships between mineralogy and the structural and chemical attributes of the soil and differentiated between agroenvironments. We collected soil samples from six profiles in diagnostic horizons of the Ferralsols and Cambisols. In the mineralogical analysis of the clay fraction, X-Ray Diffraction was used to identify mineral peaks of clay and iron oxides. The physical and chemical properties of the soils were determined. The multivariate statistical technique was applied to process the data. The clay minerals identified were hematite, goethite, kaolinite, and illite. The principal component analysis allowed for the separation of environments according to soil density, Fed and Mg2+ for developed soils, and potassium, weighted average diameter, microporosity, total organic carbon, sodium, the sum of bases, calcium, total porosity, aeration, potential acidity, and Feo discriminated developing soils. This study revealed that the clay fraction influenced the structural attributes of the soil according to the degree of soil development. Two profiles presented atypical situations: High contents of crystallized iron in Cambisols and illite peaks in Ferralsolos. These mineralogical results are not commonly found in the literature, highlighting the potential for further studies. The answers concerning the mineralogy of semiarid soils in Brazil and the world show similarity.

Soil structure affects plant growth factors in agroecosystems. The relationships of these factors with soil texture and chemical attributes are important to differentiate environments. The objective of this work was to evaluate the relationship of soil structural attributes with physical and chemical attributes of different soils to differentiate environments, using multivariate statistics. The research was carried out in the Terra da Esperança Settlement Project, in Governador Dix-Sept Rosado, RN, semiarid region of Brazil. Ten soil profiles were evaluated: Haplustepts in a conventional area (1CA); Haplustepts in a collective area with (2CA); Haplustepts in an agroecological area with native forest (3AGRO); Eutrustox in a native forest (4NF); Calciustolls in a conventional area of pasture (5CAP); Haplustepts in a native forest (6NF); Haplustepts in an native forest (7NF); Usticfluvents in a permanent conservation area with Licania rigida (8PPA); Haplustepts in a native forest (9MN); and Haplustepts in a collective area with Spondias spp. (10SP). Ten soil samples were collected and analyzed by horizons in volumetric rings and in soil blocks (aggregate analysis), with three replications. Structural, physical, and chemical attributes were evaluated. The data were subjected to multivariate statistical analysis, using correlation matrix, cluster analysis, and factorial analysis considering the factors as principal components. According to the factorial analysis, Factor 1 (F1) and Factor 2 (F2)—F1 consisting of clay, Ca2+, Na+, sum of bases, and base saturation (V), and F2 consisting of cation exchange capacity (CEC), total organic carbon, macroporosity, particle density, K+, and microporosity—were essential to differentiate the environments. The cluster analysis formed four groups. The structural groups showed greater similarity, denoting the relationship between source material and land use, followed by the chemical groups P, K+, CEC, Ca2+, V, and pH for the Calciustolls; the structural weighted mean diameter, geometric mean diameter, soil aggregates larger than 2 mm, plasticity index, and plasticity limit for the Eutrustox; and the physical and chemical attributes EC, Na+, Silt, macroporosity, total calculated porosity, aluminum saturation, total sand, volumetric moisture, Mg2+ and particle density for the Haplustepts and the Usticfluvents. The clay fraction presented correlation with chemical attributes (F1) for the distinction of soil classes and land uses. The soil classes presented eutrophic character (V ≥ 50%) as a function of the Na+ and Ca2+ contents, including the Eutrustox (4NF), despite its lower contents when compared to the other soil classes. This is a local peculiarity due to the climatic pattern of the Brazilian semiarid region.

A estrutura do solo desempenha relação com os fatores de crescimento vegetal (água, ar, calor, nutrientes e resistência à penetração de raízes), sendo essencial a manutenção e/ou melhoria dos seus atributos. O presente estudo objetivou avaliar as frações inorgânicas do solo e analisar suas inter-relações com atributos estruturais. A pesquisa ocorreu no período de agosto de 2017 a agosto de 2018, sendo realizada a coleta de amostras de solo com estrutura deformada e indeformada, nas classes de Latossolo, Chernossolo, Cambissolos e Neossolo, no Projeto de Assentamento Terra da Esperança, situado no Município de Governador Dix-Sept Rosado, Região Semiárida do Rio Grande do Norte. Foram determinados os atributos texturais (areia, silte e argila), macroporosidade, microporosidade, porosidade total calculada, porosidade total determinada, porosidade de aeração, densidade do solo, umidade gravimétrica e umidade volumétrica. Os resultados foram interpretados utilizando a técnica da estatística multivariada na distinção dos ambientes. Foram constatadas correlações significativas entre a densidade do solo e as variáveis densidade de partículas, porosidade total determinada, porosidade total calculada, microporosidade, macroporosidade, porosidade de aeração e a fração argila. A porosidade total determinada apresentou correlação com a microporosidade, nos Cambissolos, evidenciando restrições à aeração. A microporosidade e a densidade do solo obtiveram correlação positiva com a fração argila, o que refletiu nos atributos estruturais, para todas as classes estudadas, com exceção do Latossolo. Conclui-se que a fração argila foi eficiente na distinção dos ambientes, apresentando correlações significativas com os atributos densidade do solo, porosidade total determinada, porosidade total calculada, microporosidade, macroporosidade e porosidade de aeração. Os ambientes para as classes de Cambissolos foram discriminados pela fração argila, enquanto o Neossolo, pela porosidade total determinada e o Chernossolo pelo silte, sendo um indicativo de solo jovem, pouco intemperizado e facilmente disperso, susceptível ao processo erosivo. A análise multivariada foi eficiente na distinção dos ambientes, evidenciado as inter-relações entre os atributos estruturais e as frações inorgânicas do solo.

The study of the soil characterization and the relation of its attributes allows a systematic proposal of the local particularities, leading to adequate practices for maintenance and/or preservation of its productive capacity. In this sense, the aim of this study was to evaluate the influence of structural attributes in association with physical and chemical soil classes, using the multivariate statistical techniques to differentiate environments. The research was carried out in the Moacir Lucena Project, located in the municipality of Apodi, RN, Brazil. Three representative environments were chosen as follows: Profile 1 (P1)-Red-yellow Latosol-Area in recovery (1AR), P2-Haplic Cambisol-Lake Area, (2AL) and P3-Eutrophic Yellow Latosol-Cashew Tree Area (3AC). The soil samples were collected in the horizons of the studied areas. Ten (10) samples were collected per horizons in volumetric rings and in soil blocks (aggregate analysis), which resulted in triplicates in the laboratory. Structural, physical and chemical attributes were evaluated. The data were analyzed using multivariate statistical techniques, with correlation matrix, clustering analysis and factorial analysis performed by the extraction of the factors into principal components. The use of clustering analysis allowed the formation of four groups for soil classes and attributes; the inorganic fractions were determinant for environmental differentiation, where the sand was discriminant for the Red-yellow Latosol and the Eutrophic Yellow Latosol, and the clay and silt for the Haplic Cambisol. Higher similarity was observed in the transition horizons of the Latosols Class. The physical and structural attributes were determinant in the dissimilarity for the Haplic Cambisol, reflecting in physical restrictions to the plant growth. The factor analysis revealed that the variables particle density (Dp), Ca2+, Mg2+, sum of bases (SB) and cation exchange capacity (CEC) for factor 1, followed by pH, P, K+, total Sand, Clay and soil density (Ds) for factor 2 are important soil attributes to distinguish the studied environments.