TESTING SOME PEDO-TRANSFER FUNCTIONS (PTFS) IN APULIA REGION

004_Buccigrossi(516)_19 27-07-2009 11:10 Pagina 19 J. of Ag. Eng. - Riv. di Ing. Agr. (2009), 1, 19-31 TESTING SOME PEDO-TRANSFER FUNCTIONS (PTFS) IN APULIA REGION Floriano Buccigrossi, Angelo Caliandro, Pietro Rubino, Mario Alberto Mastro 1. Introduction The knowledge of the soil moisture vs. soil water matric potential is used to study irrigation and drainage planing, to determine the soil water storage capacity (plant available water), to study the solute movement, plant growth [Stanhill 1957] and water stress. Hydraulic soil characteristics can be determined directly through physical and chemical laboratory analyses or indirectly by physical-chemical characteristics of pedological horizons [Rawls 1991] that affect soil water retention, such as sand, silt, clay content (particle size distribution) organic matter or organic carbon and total CaCO3 content, soil bulk density, aggregate size distribution, free iron oxide: parameters easely to determine, quickly and at low cost [Jamison 1958; Prebble 1959; Salter 1965 a; Salter 1965 b; Petersen 1968 b; Torrent 1983; Williams 1983; McKeague 1987; Wösten 1988; Lin 1999; Rawls 2001; Rawls 2002 a; Rawls 2002 b; Pachepsky 2003; Rawls 2003]; recently also topografic variables have been introduced such as altitude and slope [Odeh 1994; Romano 2002; Leij 2004]. For this derivation PedoTransfer Functions (PTFs), expression used by Bouma (1989), can be utilized. The use of PTFs to estimate some hydrologic soil characteristics is based on three fundamental principles [Ungaro 2001]: – the PTF’s parameters are directly correlated with particle size distribution and other physical-chemical soil characteristics and parameters [Nielsen 1958; Lund 1959]; – the water content values can be estimated at specific matric potentials, depending from available data; ___________ Paper received 25.09.2007; accepted 13.01.2009 BUCCIGROSSI F. Post-Doctor (), CALIANDRO A. full professor (), RUBINO P. full profes- sor (), MASTRO M.A. high technical skills () respectively; Dipartimento di Scienze delle Produzioni Vegetali, Università di Bari, via Amendola 165/A, 70125 Bari, Italy afterwards, entire water retention curves are derived; – at specific matric potentials values, a physic-empirical relationship is always defined between particle and pore size distribution and soil water content. PTFs field research is more and more dynamic such that has produced results generally satisfying even if the large majority of study have locality importance and empirical meaning [Petersen 1968 a; Maclean 1972; Ahuja 1985; Aina 1985; Meng 1987; Daamen 1990; Bell 1995; Tomasella 1998; Tomasella 2000; Hodnett 2002; Rajkai 2004]. Wide data sets have been utilized for PTFs development such us UNSODA [Nemes 2001; Nemes 2003], HYPRESS (European database with 1700 soil profiles and 5000 soil samples) [Wösten 1999], WISE (World Inventory of Soil Emission Potentials) [Batjes 1996], GOLD and the USDA Natural Resource Conservation Service pedon database, provided by homonymous society. PTF models can be classified on the basis of nature and type of the input parameters: – models utilizing physical-chemical parameters; – models utilizing a physical-empirical approach estimating the water soil retention capacity throught pore size distribution [Brutsaert 1966; Farrel 1972; D’Hollander 1979] or particle size distribution and soil bulk density [Arya 1981; Haverkamp 1986; Tyler 1989]. Moreover, the first models can be differentiated in: – linear regression models [Gupta 1979 b; De Jong 1983; Puckett 1985; Rawls 1986]; – non-linear regression and exponential models. The last models are divided into three general groups and for their use the following perameters are estimated: – the original parameters of van Genuchten equation [van Genuchten 1980] for determining the water soil retention curve [Rawls 1985; Wösten 1988; Vereecken 1989; Simota 1996; Scheiinost 1997]; – the parameters of Campbell equation (1974) [Ghosh 1980; Cosby 1984; Cresswell 2000]; – the parameters of Brooks & Corey equation (1964) that, as the previous equations, relate the matric 004_Buccigrossi(516)_19 27-07-2009 11:10 Pagina 20 20 potential to the water soil content [Saxton 1986; Mayr 1999]. For the models that use physical-chemical parameters different levels of informations can be defined; each one individualizes one or more PTFs. According to the available data stored in the data base, it is possible to select the following PTF groups [Ungaro 2001]: Level 1: variables necessary are one or more particle size fractions (sand, silt and clay) [Stirk 1957; Nielsen 1958; Salter 1966; Aina 1985; Saxton 1986]; Level 2: variables necessary are one or more particle size fractions and organic matter content or soil bulk density [Salter 1969; Rawls 1982; Aina 1985; Rawls 1985] ; Level 3: variables necessary are one or more particle size fractions , organic matter (or organic carbon) content and soil bulk density [Gupta 1979 b; De Jong 1983; Vereecken 1989; Simota 1996]; Level 4: variables necessary are one or more particle size fractions, organic matter (or organic carbon) content, soil bulk density and volumetric water content at –33 and – 1500 kPa [Rawls 1982]. The objective of this study is to evaluate the applicability of six PTFs to estimate the volumetric water content at the field capacity and at the wilting point in soils of Apulia Region, utilizing soil samples deriving from pedons studied to build up the regional pedological map. 2. Materials and methods 2.1 Soil samples set A data set of 361 soil samples collected from 185 pedological profiles (pedons) on Apulian territory have been used for this research (figure 1). For each pedon, one or more soil samples derive from one or more pedological soil layers, respectively. The soils, according to USDA texture classification, belong to the textural compositions listed in table 1. Before making physical-chemical laboratory analyses, soil samples have been air-dried and 2 mm mesh sieved. 2.2 Physical-chemical laboratory analyses On sieved samples, organic matter content (Walkley-Black method), particle size fraction [according with USDA texture classification (table 1 and figure 2): coarse sand (2 ≥ diameter (d) ≥ 0.1 mm), fine sand (0.1 ≥ d ≥ 0.05 mm), coarse silt (0.05 ≥ d ≥ 0.02 mm), fine silt (0.02 ≥ d ≥ 0.002 mm) and clay (d ≤ 0.002 mm) (pipette method and determination of coarse sand with humid sieved)], water content (% soil dried weight) at –33 [Field Capacity (FC)] and –1500 kPa [Wilting Point (WP)] with porous plates in Richards pressure chambers [Richards 1947; 1949] have been determinated. Soil bulk density (ρb) can be directly determinated or estimated through specific models and/or PTFs [Curtis 1964; Saini 1966; Heinonen 1977; Gupta 1979 a; Alexander 1980; Rawls 1989; Leonavičiutė 2000]; in this case, having only soil samples 2 mm mesh sieved, the following equation [Adams 1973; Rawls 1982] has been applied: where: o.m.: organic mat (...truncated)