Reproduced from Soil Science Society of America Journal. Published by Soil Science Society of America. All copyrights reserved. The Geochemistry of Phosphorus in Peat Soils of a Semiarid Altered Wetland M. I. Litaor,* O. Reichmann, K. Auerswald, A. Haim, and M. Shenker ABSTRACT Kinneret (Serruya and Berman, 1976), the only fresh- water lake in Israel, which provides 25% of the country’s An understanding of P transformations in altered wetlands has drinking water, relatively little is known on the geochem- mainly developed from temperate and humid regions with neutral to acidic soils. Little is known regarding downstream water quality impact istry of P in these peat soils. of P transformations in semiarid wetlands that undergone repeated Other effects of the drainage of the Hula Wetland were cycles of drying and rewetting. The P geochemistry was studied using rapid oxidation of OM and continuous internal confla- the Hedley fractionation scheme in the altered peat soils of the Hula gration of the oxidized peat soils, leading to subsidence Valley, Israel. The peat soils were sampled according to the peat (approximately 2 m below the original surface) that in- depth and redox potential characteristics. The mean total P concentra- duced partial reflooding of the drained area. To reverse tion (P t ) in the surface peat horizons (1190  300 mg kg -1 ) was some of the negative consequences of the drainage of significantly higher than in the anaerobic (E H -220 mV) peat layers Lake Hula and the surrounding wetlands, a small 100- (650  260 mg kg -1 ). The concentrations of P in all fractions except the most labile P were significantly higher in the aerobic (E H = 400 ha lake (Agmon) was engineered in 1994, covering the mV) peat layers. The predominant extractable fractions in the surface least agriculturally productive peat soils in the Hula peat horizons were Ca-P extracted by 1 M HCl (21–60% of P t ), Iron- Valley (Fig. 1). The creation of the new lake and the P extracted by 0.5 M NaOH (11–41% of P t ), and residual P extracted elevation of the water table in the center of the Hula by H 2 SO 4 (20–40% of P t ). The source of the Ca in the Ca-P fraction Valley by at least 60 cm (Tsipris and Meron, 1998) have was mainly from gypsum dissolution following the rewetting cycles. transformed the relatively dry oxidized peat soils to The results clearly showed that the drainage of these wetlands facili- wet and anaerobic soil environs. Current management tated rapid organic matter (OM) oxidation, release of organically bound metals and P followed by sesquioxides and gypsum precipita- protocol for the valley calls for relatively high ground tion. These geochemical transformations enhanced the P t concentra- water level, which ensured that the rewetting of the tion per mass of altered peat soil and changed the P distribution oxidized peat soils would continue indefinitely. This re- among the different pools. Most of the P is currently associated with wetting practice may increase P discharge into Lake Kin- Fe oxides and hydroxides and/or coprecipitated with Ca. neret, which in turn may enhance eutrophication. Hence, an understanding of the dynamics of P in the altered peat soils of the Hula Valley is required to improve man- F resh water wetlands are nutrient sinks that effi- agement strategies for the upper catchment of the Jor- ciently process and store N and P, thus reducing the dan River. potential of eutrophication in downstream lakes (Rich- It is hypothesized that the drainage of the Hula Wet- ardson, 1985; Sharpley and Rekolainen, 1997). The drain- land caused a sequence of processes: (i) rapid oxidation ing of Lake Hula and the elimination of its surrounding of the acidic peat soils, (ii) release of organic-bound swamps, about 20 km upstream from the Jordan River metals and P followed by (iii) the oxidation of the re- inflow to Lake Kinneret, to increase the arable land in leased metals that resulted in rapid adsorption and/or northern Israel during the mid 1950s, removed this cru- coprecipitation of Fe-P and to a lesser extent Mn-P and cial nutrient sink. Consequently, increased suspended Al-P phases. The latter was mainly affected from the material and nitrate loading into Lake Kinneret from concurrent change in pH of the acidic peat soils from the Hula Basin via the Jordan River were observed (e.g., pH of 4 to neutral. In the more alkaline peat soils most Serruya et al., 1969; Stiller, 1979; Inbar, 1982). The bio- of the released P was coprecipitated in Ca-HCO 3 –P geochemistry of C and N in the peat soils of the Hula phases. The major objective of the research was to pro- Valley has received much attention in past years (Avni- vide quantitative information on P geochemistry in the melch et al., 1978; Brenner et al., 1978) resulting in more altered peat soils of the Hula Valley and to test the precise agricultural practices that reduced nitrate seep- above hypothesis using the Hedley sequential fraction- age from these soils. However, although P is more im- ation methodology. This investigation is the first step portant in regulating algal growth in downstream Lake in gaining better understanding of the interaction among the various P pools in the altered peat soils and will M.I. Litaor, Dep. of Biotechnology and Environmental Sciences, Tel- facilitate the foundations for testing the premise that Hai College, Upper Galilee 12210, Israel; O. Reichmann, A. Haim, long-term rewetting of the peat soils will eventually and M. Shenker, Dep. of Soil Science, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew Univ. of Jerusalem, result in a significant change in the P pools due to the Rechovot 76100, Israel; K. Auerswald, Dep. of Grassland Science, reduction of Fe oxides and the dissolution of gypsum Technol. Univ. Muenchen, Am Hochanger 1, D-85350 Freising- which in-turn will increase the Ca-P pool. Weihenstephan, Germany. Received 28 Oct. 2003. *Corresponding author (litaori@telhai.ac.il). Abbreviations: CBD, citrate-bicarbonate-dithionite; EC, electrical Published in Soil Sci. Soc. Am. J. 68:2078–2085 (2004).  Soil Science Society of America conductivity; OM, organic matter; P i , inorganic phosphorus; P o , or- ganic phosphorus; P t , total phosphorus. 677 S. Segoe Rd., Madison, WI 53711 USA 2078