Spatial variability of the physical attributes of soil under pasture

Abstract

RESUMO -O objetivo desse trabalho foi avaliar a variabilidade espacial de atributos físicos do solo para áreas de Latossolo, Argissolo e Cambissolo ocupadas por pastagens. O conhecimento dessa variabilidade é importante, pois ela influencia a qualidade das pastagens e a recarga de água subterrânea. Foram coletadas 154 amostras georreferenciadas para cada área de estudo. Para analisar os dados foi usada a estatística descritiva e a geoestatística. A dependência espacial ocorreu para a maioria dos atributos físicos: condutividade hidráulica em solo saturado e densidade do solo para as três classes de solos; microporosidade, macroporosidade e porosidade total para as áreas de Cambissolo e Latossolo. Os resultados da estatística descritiva e o fato do padrão da dependência espacial não ter se mantido constante indicam que as classes de solo, juntamente com a declividade e o uso da terra influenciaram a variabilidade espacial dos atributos físicos do solo analisadas e que a média não é suficiente para representar a distribuição espacial das variáveis analisadas. A malha de amostragem usada é adequada, pois permitiu captar a dependência espacial da maioria das variáveis analisadas.Palavras-chave: Física do solo. Uso da terra. Geoestatística. ABSTRACT -The aim of this work was to evaluate the spatial variability of the physical attributes of the soil in areas of a Latosol, Argisol and Cambisol under pasture. Knowledge of such variability is important, as it influences the quality of the pasture and groundwater recharge. For each study area, 154 georeferenced samples were collected. To analyse the data both descriptive statistics and geostatistics were used. Spatial dependence was seen for most of the physical attributes; saturated hydraulic conductivity and bulk density for the three soil classes; and microporosity, macroporosity and total porosity in the areas of Cambisol and Latosol. The results of the descriptive statistics, and the fact that the pattern of spatial dependence did not remain constant, show that the class of soil, together with the slope and land use, influenced the spatial variability of the physical attributes of the soil being analysed, and that an average value is not enough to represent the spatial distribution of the analysed variables. The sample grid that was used is adequate, making it possible to capture the spatial dependence of most of the variables being analysed.

Spatial variability of soil physical-hydric attributes under bovine trampling in agreste of Pernambuco State, Brazil

“…The TP and K 0 decreased as PR and BD increased (Figures 2, 3, 4, and 5), the results similar to findings of Guimarães et al (2016). According to Mion et al (2012), TP shows a strong correlation with PR, which tends to increase as TP is reduced.…”

“…The PR for 0.0 -0.1 m showed high variability, as also reported by Mion et al (2012), who analyzed the spatial variability of the physical attributes in a yellow argisol under alternate sheep grazing; those authors attributed their results to high variability of the average, showing a distribution with high heterogeneity of data. After grazing, BD and TP had low variability for all depths sampled, which was also found by Guimarães, Junior, Marques, Santos, and Fernandes (2016), who evaluated the spatial variability of soil physical attributes in latosol, argisol, and cambisol pastures and reported that their results were due to bovines having preferred spots in a pasture, which can promote greater soil heterogeneity. The PR, GM, and K 0 showed moderate variability (Table 3).…”

“…Thus, the variability of this variable can be considered aleatory, and lower spacing will be necessary for sample collection to detect spatial dependence, as suggested by Cambardella et al (1994). Likewise, Guimarães et al (2016) reported a pure nugget effect for TP at 0.10 and 0.15 m after applying 10 x 10 m spacing to estimate the spatial dependence of the physical attributes of soil under pasture. The spatial dependence degree (SDD) was classified as strong for other variables analyzed.…”

“…According to Reichert, Reinert, and Braida (2003), a density values of 1.65 kg dm -3 in sandy soils indicates a high probability of root growth restriction. In conventional grazing over 10 years, Guimarães et al (2016) reported 1.27 kg dm -3 BD. The BD increase, which occurred mainly at the shallowest depths, can be related to high-intensity bovine trampling and, consequently, pasture degradation.…”

Sampling Design of Soil Physical Properties in a Conilon Coffee Field

“…Similar fits were found by Resende et al (2014) for clay, silt, and total sand in a Typic Hapludults, by Sana et al (2014) for clay in a Typic Hapludox, and by Guimarães et al (2016) for Ma, TPV, and BD in an Oxisol.…”