Variabilidade espacial de propriedades hidrodinâmicas de um Neossolo Regolítico sob pastagem e caatinga

Abstract

R E S U M OAs propriedades hidrodinâmicas dos solos de pastagem e de caatinga, são afetadas por diversos fatores, sobretudo associados a aspectos espaciais e temporais relacionados às diferentes características dos sistemas radiculares e das taxas de pisoteio do gado, mas poucos resultados que avaliem o efeito da magnitude dessas fontes de variabilidade sobre as propriedades hidrodinâmicas dos solos têm sido relatados na literatura. Objetivou-se analisar a variabilidade espacial dos parâmetros que descrevem as curvas de retenção (van Genuchten) e da condutividade hidráulica (Brooks & Corey) da água do solo, obtidos com a metodologia denominada "Beerkan", que se baseia em ensaios de infiltração simplificados e nas informações texturais do solo. Para isto foram realizadas medidas de infiltração e coletadas amostras de solo em duas áreas: uma área de pastagem (Brachiaria decumbens) e outra de caatinga. Os resultados mostraram que o uso do solo com pastagem alterou significativamente as propriedades analisadas quando comparadas com as do solo com caatinga, com alterações mais expressivas na densidade do solo e na condutividade hidráulica. A análise geoestatística identificou a existência de dependência espacial de alguns atributos estudados, permitindo o mapeamento das áreas experimentais. Spatial variability of hydrodynamic properties of a Regolithic Neosoil under pasture and 'caatinga' A B S T R A C TThe hydrodynamic properties of soils under pasture and 'caatinga' (native dry forest) are affected by several factors, mainly associated with spatial and temporal aspects, due to differing root characteristics or livestock trampling rates, but few results that evaluate the effect of the magnitude of these sources of variability in the hydrodynamic properties of soils have been reported in the literature. The objective of this study was to analyse the spatial variability of parameters of water retention (van Genuchten) and hydraulic conductivity (Brooks & Corey) curves, obtained with the "Beerkan" methodology based on simple infiltration experiments and soil texture data. These measures were obtained for two sampled areas: an area of pasture (Brachiaria decumbens) and another one of 'caatinga' . The results showed that the use of pasture altered significantly the analysed properties of soil when compared to the ones with the soil under 'caatinga' , and that the most significant changes were found in soil density and hydraulic conductivity. The geostatistic analysis identified the existence of spatial dependency of the studied attributes allowing the mapping of experimental areas. Palavras-chave:manejo do solo Beerkan geoestatística

Water erosion in Caatinga and degraded pasture areas in semiarid region

“…However, the slight increase in soil density in the PD area led to low values of saturated hydraulic conductivity, sorption and infiltration (Table 2). Contrary to the results found for soil bulk density for the study, Oliveira Júnior et al (2014) verified that soil management with pasture significantly altered the soil density, which for the pasture was 1.39 g cm -3 and for the Caatinga vegetation was 1.30 g cm -3 , proving that the intensive use of these grazing areas promotes changes in the physical characteristics of the soil.…”

“…According to Oliveira Júnior et al (2014), the sorptivity translates the capacity of the soil to absorb water by capillarity and depends essentially on the variation of the volumetric water content between the beginning and the end of the infiltration. These same authors also contacted reductions in Ksat and S in pasture area, with a reduction of 20% when compared to soil under Caatinga vegetation for S. According to Parente et al (2010), a well-structured, less compacted soil can have higher values of sorptivity and hydraulic conductivity and, due to the organic matter content, can retain more water.…”

An Alert Regarding a Common Misinterpretation of the Van Genuchten α Parameter

“…In Brazilian soil physics literature, several authors relate the inverse of parameter α to the air-entry pressure, in analogy to the BC parameter h b . Some use this kind of identification when describing VG parameters (Souza et al, 2008a;Lima et al, 2014;Oliveira Júnior et al, 2014), others when explicitly interpreting results of α values to the air-entry pressure (Souza et al, 2008b;Silva et al, 2009;Mota et al, 2017). In international literature, a similar description can sometimes be found (Pollaco and Mohanty, 2012;Aschonitis and Antonopoulos, 2013;Aschonitis et al, 2015;Dokoohaki et al, 2017).…”

Land-use change effect on the hydro-dynamic characteristics of soil in the Brazilian semi-arid region

“…15 n. 2, e2368 -Taubaté 2020 as well as inspiring alternative guidelines for more integrated plans that combat desertification. Oliveira Junior et al (2014) evaluated the impact of pasture on the hydrodynamic properties of a regolithic neo-soil in the Agreste Region of Pernambuco, and observed that the use of the soil for pastureland significantly altered its properties when compared with those of the natural Caatinga soil, mainly with regard to soil density and hydraulic conductivity.…”