Anisotropy of Pore Size Classes’ Connectivity Related to Soil Structure Under No Tillage

Abstract

No-tillage (NT) systems have been increasing during the last several decades. Development of a near-surface layer of laminar structure under NT has also been reported. The objectives of this work were to determine whether preferential connectivity of different pore size classes in two differently textured soils under NT exists and to propose a new index of pore connectivity based on water flux (Cw). The study was carried out at two sites in the Pampas Region of Argentina under long-term NT. Site 1 had a loamy A-horizon, and Site 2 had a sandy loam A-horizon. Undisturbed samples were extracted in vertical and horizontal directions within the first 8 cm of the soil. Saturated hydraulic conductivity (K s ), nearsaturated hydraulic conductivity (h: −50, −100, −200, −300, and −500 cm), pore size distribution from water retention curve, and total porosity were determined. The index of pore connectivity based on water flux, Cw, was developed as a ratio between K and pore volume for each pore size class. Site 1 showed laminar structure in the A-horizon, whereas Site 2 showed a blocky structure. We found a preferential connectivity in horizontal direction of macropores in Site 1. The index of pore connectivity was useful to assess the presence of preferential orientation of different pore size classes. In future studies, the connectivity of the different pore size classes should not be neglected.

Soil Physical Quality and Soybean Yield as Affected by Chiseling and Subsoiling of a No-Till Soil

“…A pore continuity index (Cw) based on water flux (Lozano et al, 2013) was calculated for each pore size family with radii between r a and r b (r a >r b ) as the ratio between K(h a ) and K(h b ) (cm h 1 ) (where h a and h b are the pressure heads at which pores with equivalent radii greater than r a and r b , respectively, drain) and the pore volume fraction occupied by this family (m 3 m -3…”

“…A pore connectivity index based on water flux (Cw) that relates hydraulically active porosity and total porosity was recently by Lozano et al (2013). This index was valuable for understanding the effects of the NT system on the connectivity of different pore size families and pore anisotropy.…”

Effects of Compaction Due to Machinery Traffic on Soil Pore Configuration

“…This effect can be determined through the measurement of saturated K in samples taken vertically and horizontally (Soracco et al, 2010;Lozano et al, 2013).…”

Variación temporal de las propiedades físicas del suelo y su impacto en la dinámica del glifosato en suelos bajo siembra directa y labranza convencional

“…La macroporosidad del suelo juega un rol sumamente importante en la infiltración del agua, incluso cuando representa una pequeña fracción de la PT (Cameira et al, 2003, Holden, 2009 de estructura está asociada a la presencia de estructura laminar superficial, particularmente en los casos de suelos de texturas franco limosas a limosas con ausencia de características vérticas (Lozano, 2014). Son varios los autores que en los últimos años han reportado el desarrollo de estructura laminar en la Región Pampeana Argentina asociada a la SD (Sasal et al, 2006, Soracco et al, 2010, Lozano et al, 2013, Álvarez et al, 2014, Sasal et al, 2017, Behrends Kraemer et al, 2017.…”

“…Bajo LC, algunos estudios reportan un aumento de la conductividad hidráulica saturada (K0), la macroporosidad y la Sortividad (S) en distintos tipos de suelos luego de la labranza, que progresivamente disminuye durante el ciclo de cultivo (Angulo-Jaramillo et al, 1997, Azevedo et al, 1998, Bormann y Klaassen, 2008. Lozano et al (2013) desarrollaron un índice de conectividad de poros basado en el flujo de agua (Cw) que relaciona la conductividad hidráulica con la porosidad, para cada familia de poros. Este índice resulta útil a la hora de estudiar el efecto de los distintos sistemas de labranza sobre la configuración del sistema poroso y su conectividad.…”