J Soils Sediments DOI 10.1007/s11368-016-1448-8
SOILS, SEC 3 • REMEDIATION AND MANAGEMENT OF CONTAMINATED OR DEGRADED LANDS • RESEARCH ARTICLE
Biochar effects on soil water infiltration and erosion under seal formation conditions: rainfall simulation experiment Vikas Abrol 1,2 & Meni Ben-Hur 1 & Frank G. A. Verheijen 3 & Jacob J. Keizer 3 & Martinho A. S. Martins 3 & Haim Tenaw 1 & Ludmilla Tchehansky 1 & Ellen R Graber 1
Received: 13 December 2015 / Accepted: 10 May 2016 # Springer-Verlag Berlin Heidelberg 2016
Abstract Purpose Soil amendment with biochar can result in decreased bulk density and soil penetration resistance, and increased water-holding capacity. We hypothesized that adding biochar could moderate the reductions in infiltration rates (IR) that occur during high-intensity rainstorms in seal-prone soils, and hence result in reduced runoff and erosion rates. The objectives were to (i) evaluate biochar potential to improve infiltration and control soil erosion, and (ii) investigate the mechanisms by which biochar influences infiltration rate and soil loss. Materials and methods Rainfall simulation experiments were conducted on two physicochemically contrasting, agriculturally significant, erosion-prone soils of Israel that are candidates for biochar amendment: (i) non-calcareous loamy sand, and (ii) calcareous loam. Biochar produced from mixed wood sievings from wood chip production at a highest treatment temperature of 620 °C was used as the amendment at concentrations from 0 to 2 wt%. Results and discussion In the non-calcareous loamy sand, 2 % biochar was found to significantly increase final IR (FIR) by
1.7 times, and significantly reduce soil loss by 3.6 times, compared with the 0 % biochar control. These effects persisted throughout a second rainfall simulation, and were attributed to an increase in soil solution Ca and decrease in Na, and a subsequently decreased sodium adsorption ratio (SAR). In the calcareous loam, biochar addition had no significant effect on FIR but did reduce soil loss by 1.3 times. There were no biochar-related chemical changes in the soil solution of the calcareous loam, which corresponds to the lack of biochar impact on FIR. Surface roughness of the calcareous loam increased as a result of accumulation of coarse biochar particles, which is consistent with decreased soil loss. Conclusions These results confirm that biochar addition may be a tool for soil conservation in arid and semi-arid zone soils. Keywords Crust . Biochar . Infiltration . Rainfall . Seal . Soil loss
1 Introduction Responsible editor: Yong Sik Ok Electronic supplementary material The online version of this article (doi:10.1007/s11368-016-1448-8) contains supplementary material, which is available to authorized users. * Ellen R Graber
[email protected] 1
Institute of Soil, Water and Environmental Sciences, The Volcani Center, ARO, Bet Dagan, Israel
2
Advance Centre for Rainfed Agriculture, Sher-e-Kashmir University of Agricultural Sciences and Technology, Jammu, India
3
Centre for Environmental and Marine Studies, Department of Environment and Planning, University of Aveiro, Aveiro, Portugal
Accelerated soil erosion and soil degradation are pressing environmental problems, resulting in degradation of ecosystem functions (Verheijen et al. 2009), reduction in soil productivity and sustainability of agriculture lands (Lal 2009, 2010), and displacement of human populations (Lonergan 1998). Arid and semi-arid regions under Mediterranean climatic conditions, which are characterized by long dry seasons followed by short wet seasons with high-intensity rainfall events, are prone to soil erosion and water loss as runoff (Ben-Hur 2008). The hot dry climate, water scarcity, and poor and erosionprone soils in these regions call for soil and water management strategies to conserve soil and water and sustain agricultural production.
J Soils Sediments
Infiltration is an important process in the hydrologic cycle; it determines water intake by the soil profile and the amount lost as runoff. Runoff is commonly accompanied by soil erosion and soil loss, which may necessitate costly remedial strategies. The infiltration rate (IR) of arid and semi-arid soils under water-drop impact is influenced mainly by seal formation at the soil surface (Hillel 1967; Morin et al. 1981; Ben-Hur et al. 1985; Ben-Hur et al. 1987). Thin surface seals (~2 mm thick), characterized by greater density, higher strength, finer pores, and lower saturated hydraulic conductivity than the underlying soil (McIntyre 1958; Gal et al. 1984; Wakindiki and Ben-Hur 2002; Assouline 2004; Lado et al. 2004a), lead to drastic decreases in IR (Morin and Benyamini 1977; Assouline and Mualem 1997; Assouline 2004). Agassi et al. (1981) suggested that the formation of a structural seal is the result of two complementary mechanisms: (i) physical disintegration of surface soil aggregates under the impact energy of the raindrops, and (ii) the physicochemical dispersion of soil clays, which migrate into the soil with the infiltrating water and clog the pores immediately beneath the surface to form the Bwashed-in^ zone. The relative importance of the latter mechanism depends on the electrolyte concentration of the soil solution and the exchangeable sodium percentage (ESP) of the soil. As the electrolyte concentration decreases and the ESP increases, the IR reduction due to seal formation is usually more pronounced (Kazman et al. 1983; Shainberg and Letey 1984). Soil erosion involves two major processes: (i) soil detachment—disintegration of soil particles from the bulk soil, and (ii) transport capacity—transport of the detached sediments, mainly by surface runoff (Watson and Laflen 1986). Thus, the IR reduction and increase of runoff and soil loss in arid and semi-arid soils are controlled mainly by destruction of the structure of the soil surface. Various organic amendments and synthetic polymers, such as polyacrylamides (PAM), have been used as conditioners to improve soil physicochemical properties and protect soils from erosion with varying degrees of success (Ben-Hur 2006; Busscher et al. 2011; Prats et al. 2014). However, the field application of PAM is problematic because of its very low solubility in water and high viscosity (Agassi and Ben-Hur 1992). Over the last decade, biochar has been increasingly studied as a soil organic amendment. The main focus of biochar research has been potential improvements in the crop production ecosystem service that may occur when biochar is added to soil (e.g., Jeffery et al. 2011). Of secondary focus in biochar research has been the attempt to understand the mechanisms underlying these effects, primarily chemical (Liang 2006; Atkinson et al. 2010) and (micro)biological (Kolton et al. 2011; Gul et al. 2015), as well as their associated regulation ecosystem services. How the addition of biochar to soil can change soil physical properties that may then affect regulation ecosystem services, such as soil hydrology, has so far received the least research attention (Masiello et al. 2015).
Of the reported biochar effects on soil physical properties, a decrease in bulk density is the most consistently reported for a wide range of biochar application rates (Jones et al. 2010; Busscher et al. 2011; Streubel et al. 2011; Pereira et al. 2012; Abel et al. 2013; Hardie et al. 2014; Peake et al. 2014; Koide et al. 2015). Soil water retention has mostly been reported to be unaffected or to increase with biochar amendment (Uzoma et al. 2011; Novak et al. 2012; Kinney et al. 2012; Devereux et al. 2012; Masiello et al. 2015), with the exception of soils rich in clay (Tryon 1948). Saturated hydraulic conductivity has been reported in some cases to increase (Asai et al. 2009; Uzoma et al. 2011; Githinji 2014; Herath et al. 2013; Lei and Zhang 2013; Ouyang et al. 2013), but also to decrease, specifically in sandy soil (Brockhoff et al. 2010). Few studies have investigated the effects of biochar on soil erodibility (e.g., Smetanová et al. 2013), IR (e.g., Busscher et al. 2010), surface runoff, and soil erosion (e.g., Asai et al. 2009; Ayodele et al. 2009; Doan et al. 2015). None were studied under controlled laboratory conditions, and information assessing the underlying mechanisms is scant. Hence, the knowledge of how biochar application mechanistically affects these properties is limited. For semi-arid regions, there is no reported evidence to date, and thus, the potential for biochar amendment to make a contribution to water management strategies in soils, especially in dry regions, is unknown. We hypothesized that biochar amendment of sealing-prone soils increases the IR and reduces erosion due to contribution of electrolytes dissolving from biochar into the soil solution. These electrolytes would serve to limit clay dispersion, aggregate disintegration, and soil sealing. To study this, two important agricultural and sealing-prone soils from Israel, a noncalcareous loamy sand (Hamra) from a semi-arid region and a calcareous loam (loess) from an arid region, were amended with biochar and subjected to episodes of intense artificial rainfall with attendant measurements of IR, soil loss, and electrolyte types and concentrations in the leachates. The specific objectives were to (i) explore the possibility of using biochar as a conservation measure in these soils for improving infiltration and controlling soil erosion, and (ii) investigate the underlying mechanisms involved in biochar impacts on IR and soil erosion.
2 Materials and methods 2.1 Soils and biochar The following two sealing-prone, agricultural soils from Israel that are candidates for amendment by biochar, while having contrasting textures and physical and chemical properties, were selected: a calcareous loam (Calcic Haploxeralf) from the northern Negev (an arid region) and a non-calcareous loam sand (Rhodoxeralf) from the coastal plain (a semi-arid region).
J Soils Sediments
The clays in the soils are predominantly montmorillonite (60 %), with illite and kaolinite in small amounts (Banin and Amiel 1970; Wakindiki and Ben-Hur 2002). The soils were collected from the top layer (0–25 cm) of cultivated fields and air-dried. Visible roots and organic residues were removed, and portions of the air-dried samples were crushed, sieved (≤2 mm), and analyzed for their general physical and chemical properties (Table 1), mechanical composition by hydrometer method (Day 1956), organic matter content using the Walkley–Black method (Allison 1965), Ca-MgCO3 content by evolution of CO2 gas upon acidification (Allison and Moodie 1965), and cation exchange capacity (CEC) and exchangeable sodium content using ammonium acetate at pH 7 (Chapman 1965). To determine soil solution properties, soil and deionized water were mixed at a 1:1.5 soil:water ratio in a 200-mL Teflon centrifuge tube; the tube was sealed with a Teflon-lined cap, shaken mechanically for 1 h at 160 rpm, and centrifuged for 10 min at 7000 rpm; the supernatant was collected; and then, electrical conductivity (EC) values and concentrations of Na+, Ca2+, and Mg2+ were measured. The Na concentration was determined using a Sherwood model 420 flame photometer and Ca and Mg concentrations by atomic adsorption spectroscopy (Perkin Elmer, Analyst 8000). The biochar used in this study was supplied by Swiss biochar (Lausanne, Switzerland) and was produced from mixed wood sievings from wood chip production, using a Pyreg 500 III pyrolysis unit at a highest treatment temperature of 620 °C, and quenched with water to 30 % water content. The biochar was dried at 60 °C until its weight stabilized before being used. The general chemical and physical biochar characteristics were carbon content = 88.9 % and ash content (550 °C) = 11.4 %, made up of CaO, K2O, MgO, and Na2O at 50.9, 14, 3.8, and 1.8 %, respectively (DIN 51729-1/-11; Eurofins laboratory). The pH was 8.13 in 0.01 M CaCl2 solution (1:5), and the EC was 1496 μS cm−1 in water solution (1:10).
was determined by dry sieving for six different fractions of particle sizes (>2.0, 1.0–2.0, 0.50–1.0, 0.05–0.25, 0.099–0.25, and
