Spatial Variability Of Chemical Properties Research Articles

Spatial distribution of soil chemical properties in the cerrado of Tocantins

Information on spatial variability of soil chemical properties is allowing an increasingly efficient management of soil fertility. This study was conducted in the municipality of Santa Rosa do Tocantins, TO, in the 2018/2019 crop year. The objectives of the study were to characterize the spatial variability of chemical properties of a dystrophic Red Latosol in the Cerrado of Tocantins using geostatistics and optimize the management of soil fertility by means of precision agronomy techniques, for more efficient input use in agricultural production areas. For the experiment, 49 soil samples were collected at 0.2 m depth, from equidistant points in a regular grid 100 m apart, over an area of ??150 ha. Each sample was composed of 5 subsamples. The soil properties evaluated included pH, bases sum, potential acidity, organic matter, total cation exchange capacity, base saturation, phosphorus, sulfur, potassium, calcium, magnesium, boron, copper, iron, manganese, and zinc. A descriptive analysis was carried out, highlighting the mean, median, minimum, and maximum values for each soil variable. In addition, the coefficients of variation, asymmetry, kurtosis, and the normality test of Kolmogorov-Smirnov were performed. The area presented significant variations in chemical and macronutrient attributes and little variation in micronutrients, except for zinc. The study reveals variations in different soil attributes and the need for correction depending on the requirements of the crop.

Comportamento dos óxidos de ferro da fração argila e do fósforo adsorvido, em diferentes sistemas de colheita de cana-de-açúcar

Na agricultura, a obtenção de maiores produtividades das culturas com base no manejo sustentável do solo tem levado a uma busca gradativa do conhecimento das variáveis envolvidas nos sistemas de produção. Determinar as causas da variabilidade dos atributos passa a ser uma etapa do planejamento estratégico no setor sucroenergético. Este trabalho teve por objetivo estudar a variabilidade espacial dos óxidos de ferro da fração argila e sua relação com atributos físicos e químicos do solo, em diferentes sistemas de colheita de cana-de-açúcar na Região de Ribeirão Preto, SP. Duas parcelas de 1 ha foram delimitadas em áreas com sistema de colheitas mecanizada e manual. Foram retiradas, em cada área, amostras de solos em 126 pontos, na profundidade de 0,00-0,25 m. Os resultados das análises mineralógicas e químicas foram submetidos às análises geoestatísticas, obtendo-se a dependência espacial, os semivariogramas e os mapas de krigagem dos atributos estudados. Para analisar a correlação espacial entre os atributos estudados, foram construídos semivariogramas cruzados. A variabilidade espacial dos atributos químicos é maior em áreas com colheita de cana crua, quando comparada com áreas de colheita de cana queimada, ao contrário dos atributos mineralógicos, que apresentaram os maiores alcances na área de cana crua. Os atributos matéria orgânica, diâmetro médio do cristal da goethita apresentaram correlação espacial negativa, enquanto a argila apresentou correlação positiva com a adsorção de fósforo nos dois sistemas de colheita de cana-de-açúcar avaliados.

Spatial Variability Analysis of Selected Soil Properties at Musayab, Babil, Iraq

Great Musayab projectwas chosen to assess spatial variability of some soil properties,and furthermore,to investigate its implications for sampling design. Two hundred and forty composited soil samples werecollected acrossthe project and thesurrounding areas. Soil properties including electrolytic conductivity (ECe),calcium carbonate (CaCO3), cation exchange capacity (CEC),as wellas sand, silt, and clay were analyzed for each sample. Classic statistical analysis showed that ECe had the highest CVwhichwas caused by some unusually high measurements. Semivariograms of allproperties were constructed,and compared to estimate thespatial variability of the soilproperties in the area. Thesemivariograms of soilproperties were best describedby aexponential model. Geo-statistical analysis showed that all the soil properties had a moderate or strong spatial dependency. Ordinary kriged maps indicated soils with high ECe, CEC, CaCO3, sand, silt, and clay in the surface horizons were found in the southern parts of the project. Water flows may be the dominant driving force for the spatial variability of chemical properties and texture parameters, implying more samples or analysis are required to achieve a similar level of precision.

VARIABILIDADE ESPACIAL DA FERTILIDADE DE NEOSSOLO QUARTZARÊNICO EM FUNÇÃO DA SUBSTITUIÇÃO DO CERRADO POR PASTAGEM

As características químicas dos solos do Cerrado brasileiro são facilmente alteradas pelas intervenções humanas. O objetivo desse estudo foi avaliar a variabilidade espacial das propriedades químicas em um Neossolo Quartzarênico Órtico típico, em função da substituição do Cerrado por Pastagem, na região de Araguaína (TO), Brasil. Foram feitas amostragens do solo em uma malha irregular em área de 13,11 ha, na profundidade de 0 a 20 cm, para determinação dos teores de matéria orgânica (MO), Al3+, P, K+, Ca2+, Mg2+ , valores de pH, soma de bases (SB), capacidade de troca de cátions em pH 7,0 (CTCpH 7), capacidade de troca de cátions efetiva (CTCe), saturação por bases - V% e saturação por alumínio - m%. As propriedades químicas do solo foram analisadas por estatística descritiva e tiveram suas médias comparadas pelo teste de Tukey, a 5% probabilidade, utilizando geoestatístico e interpolação por krigagem ordinária. Os alcances de dependência espacial dos atributos químicos pH e Ca2+ do solo foram menores que os demais (MO, Al3+, P, K+, Mg2+, SB, CTCpH 7, CTCe e V%), indicando que eles apresentam menor continuidade na distribuição espacial em Neossolo Quartzarênico Órtico típico, em função da conversão do Cerrado em Pastagem.

Terrain forms and spatial variability of soil properties in an area cultivatedwith citrus

The technique of precision agriculture and soil-landscape allows delimiting areas for localized management, allowing a localized application of agricultural inputs and thereby may contribute to preservation of natural resources. Therefore, the objective of this work was to characterize the spatial variability of chemical properties and clay content in the context of soil-landscape relationship in a Latosol (Oxisol) under cultivation of citrus. Soil samples were collected at a depth of 0.0-0.2 m in an area of 83.5 ha planted with citrus, as a 50-m intervals grid, with 129 points in concave terrain and 206 points in flat terrain, totaling 335 points. Values for the variables that express the chemical characteristics and clay content of soil properties were analyzed with descriptive statistics and geostatistical modeling of semivariograms for making maps of kriging. The values of range and kriging maps indicated higher variability in the shape of concave topography (top segment) compared with the shape of flat topography (slope and hillside segments below). The identification of different forms of terrain proved to be efficient in understanding the spatial variability of chemical properties and clay content of soil under cultivation of citrus.

Spatial variability of soil chemical properties after coffee tree removal

Assessing the spatial variability of soil chemical properties has become an important aspect of soil management strategies with a view to higher crop yields with minimal environmental degradation. This study was carried out at the Centro Experimental of the Instituto Agronomico, in Campinas, São Paulo, Brazil. The aim was to characterize the spatial variability of chemical properties of a Rhodic Hapludox on a recently bulldozer-cleaned area after over 30 years of coffee cultivation. Soil samples were collected in a 20 x 20 m grid with 36 sampling points across a 1 ha area in the layers 0.0-0.2 and 0.2-0.4 m to measure the following chemical properties: pH, organic matter, K+, P, Ca2+, Mg2+, potential acidity, NH4-N, and NO3-N. Descriptive statistics were applied to assess the central tendency and dispersion moments. Geostatistical methods were applied to evaluate and to model the spatial variability of variables by calculating semivariograms and kriging interpolation. Spatial dependence patterns defined by spherical model adjusted semivariograms were made for all cited soil properties. Moderate to strong degrees of spatial dependence were found between 31 and 60 m. It was still possible to map soil spatial variability properties in the layers 0-20 cm and 20-40 cm after plant removal with bulldozers.

Effect of Agricultural Intervention on the Spatial Variability of some Soils Chemical Properties in the Eastern Plains of Colombia

A B S T R A C T Growing demand for food exerts pressure on natural resources and may lead to the expansion of agricultural frontiers in developing countries. Most of this pressure appears in tropical zones, in native savannahs, with naturally infertile soils prone to degradation. Crop management in these regions is based on generalized estimates, leaving aside the inherent soil variability, leading to low production efficiency and high risk of environmental damage. This study aims at determining the spatial variability of some chemical properties, including organic carbon, pH, exchangeable acidity, exchangeable aluminum, P, Ca, Mg, K and Na for two Oxisols with different levels of agricultural intervention, in Puerto Lopez, Colombia, in order to identify guidelines for site-specific management. A forty-two point grid (25 · 25 m) was established for samplings at two depths: 0-100 and 100-200 mm. Descriptive statistics and geostatistics were used to analyze soil properties spatial dependence. Variogram models were obtained and from them maps of properties were drawn using ordinary punctual kriging. The results showed that spatial variability of the soil chemical properties depends upon the use of amendments, fertilizing methods, tillage and the inherent characteristics of each variable analyzed. A greater influence of the agricultural intervention on spatial variability was evident in the upper 100 mm of soil. Spatial dependence was found for most of the studied soil properties. However, K and Na presented variograms with pure nugget effects and/or very short ranges. The information generated is a base to derive guidelines for site-specific agriculture.

Three-dimensional spatial variability of chemical properties around a monitored waste emplacement tunnel

Regulatory requirements and scientific needs require that the response of the geological system to emplacement of high level radioactive waste be monitored for long time periods. This monitoring activity is intended to establish the extent to which predicted behavior matches the actual response of the geological system to waste emplacement. To accomplish this goal, field measurements must be made at a spatial resolution that will determine whether the changes in parameters that are monitored conform to predicted evolutionary patterns. From the perspective of thermohydrological and geochemical parameters, key measurements will consider pore water compositional evolution and changes in matrix and fracture saturation in the near vicinity of waste emplacement tunnels. A massively parallel high performance computational platform (a 1200 processor IBM SP-2) was used to conduct three-dimensional, high resolution simulations to ascertain the spatial variability to be expected during a monitoring period. The results show that spatial variability in certain chemical parameters below waste emplacement tunnels provides robust targets for monitoring, but will require sampling on the scale of 10 s of centimeters in some locations, in order to rigorously test models. Chemical variability induced by relatively small changes in waste package heat output suggests that designing a monitoring program that will rigorously test model predictions will likely require high resolution, three-dimensional simulations of the “as-built” monitoring tunnels.