Abstract
Liming can influence crop growth by altering pore geometry, pore size distribution and water retention characteristics in acid soils. The aim of this work is to determine liming effects on the soil structure based on analysis of water retention data using a cubic spline adjustment function. For that, the authors investigated the effect of three lime rates (0, 15 and 20 t ha-1) on soil water retention characteristics and pore size distribution of a silty-clay "Cambissolo Háplico Alumínico" (Dystrudept) located in the SE region of the Paraná State, Brazil. Soil cores were collected after 31 months of the experiment at 0-10 cm and 10-20 cm soil layers. Eleven matric potentials (from 0 to -7000 cm H2O) were employed to calculate soil water retention and pore size distribution curves. The pore size distribution curves revealed trimodal soil porosity with three distinct peaks. Equivalent pore diameters ranging from 9.18 µm to 13.18 µm separated structural and matrix domains. Small differences exist in the pore size distribution curves due to liming and between layers for all peaks. With no-till plus surface liming, the volume of large pores diminished at the two layers and the volume of small pores increased at the surface layer.
Highlights
IntroductionThe soil water retention curve (SWRC) and the pore size distribution curve (PSDC) have been widely used to characterize the soil structure (Assouline et al 1997, Hajnos et al 2006, Pires et al 2008, 2017a, Cássaro et al 2011, Dos ReisAgrarian SciencesAn Acad Bras Cienc (2019) 91(3)LIMING EFFECTS ON SOIL WATER RETENTION DATAIn order to determine the SWRC, the van Genuchten model (van Genuchten 1980) is often employed to parameterize data of soil water content (θ) as function of the matric potential (h) (Auler et al 2014, 2017b, Pires et al 2017b, Naveed et al 2014)
From the SWRCs (Fig. 2a-b), it is possible to observe that L15 and L20 present similar behavior in comparison to lime doses of 0 (L0), at both soil layers
The silty-clay “Cambissolo Háplico Alumínico” (Dystrudept) presented a trimodal porosity when analyzed by the cubic spline adjustment considering all treatments and both layers (0-10 cm and 10-20 cm)
Summary
The soil water retention curve (SWRC) and the pore size distribution curve (PSDC) have been widely used to characterize the soil structure (Assouline et al 1997, Hajnos et al 2006, Pires et al 2008, 2017a, Cássaro et al 2011, Dos ReisAgrarian SciencesAn Acad Bras Cienc (2019) 91(3)LIMING EFFECTS ON SOIL WATER RETENTION DATAIn order to determine the SWRC, the van Genuchten model (van Genuchten 1980) is often employed to parameterize data of soil water content (θ) as function of the matric potential (h) (Auler et al 2014, 2017b, Pires et al 2017b, Naveed et al 2014). The adjustment function referred as cubic spline fits well to almost all (θ, h) data sets and it provides greater details when interpolating the SWRC (Kastanek and Nielsen 2001). This function makes it possible to identify multimodal structured soils through the PSDC (Lipiec et al 2006, Ogunwole et al 2015, Pires et al 2017c). Soil acidity is considered a limiting factor to the yield in extensive areas of the world, especially in tropical and subtropical regions In this way, liming is a known practice to increase the soil pH and to ameliorate the availability of nutrients such as calcium (Ca) and phosphorum (P) to plants (Edmeades and Ridley 2003). The surface liming (without incorporation methods) is usually chosen when no-till system (NTS) is used (Godsey et al 2007, Barbieri et al 2015, Joris et al 2016, Dos Santos et al 2018). Caires et al (2006) showed that surface liming on NTS stood out in terms of soil structure conservation and economic return
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