University of Technology and Agriculture, Department of Soil Science and Biochemistry, 6 Bernardyñska St., Bydgoszcz, Poland

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1 Scientific registration n o : 1338 Symposium n o : 6 Presentation : poster Distribution of total and the DTPA-extractable selenium in soil profiles from Kujawy Upland (Poland) Distribution de la teneur en sélénium total et extractible au DTPA, dans les profils de sol de la région de Kujawy (Pologne) BOROWSKA Katarzyna University of Technology and Agriculture, Department of Soil Science and Biochemistry, 6 Bernardyñska St., Bydgoszcz, Poland Introduction The selenium content of soils and plants of some regions has been the subject of research due to its deficiency as well as its toxicity for people and animals. The earlier studies (Borowska et al.,1994; Borowska, 1995) have shown that arable soils of the Pomorze and Kujawy region have a very low total selenium content, therefore, many agricultural areas produce crop plants and forages with a low selenium content. The knowledge of total microelements content is sufficient for the estimation of the soil environment status, whereas for assessing their availability it is necessary to determine their various forms, especially exchangeable and water-soluble ones. DTPA (diethylenetriaminepentaacetic acid) solution is one of the extractants used in extraction of trace elements forms of low mobility, but available to plants, (Cieœla et al., 1994) The objective of the study was to determine total and DTPA-extractable selenium in some selected pedons from the Kujawy Upland (Poland). Materials and methods Soil samples were collected from nine soil profiles of alfalfa plantations located in the Pomorze and Kujawy region. The soils represented major soil types of this region. According to FAO classification soils under the study were classified as Gleyic Phaeosems (Kujawy black earths), Mollic Cambisols (typical brown soils) and Luvisols (lessivé soil). The soils developed on the glacial till of the Baltic glaciation ground moraine (Würm) (Cieœla, 1968). Soil samples were air dried and sieved through 1 mm screen. Texture of the soils, ph, organic matter content were analysed by commonly used methods. The extraction of soil samples with DTPA was carried out according to 1

2 the Lindsay and Norvell (1978) procedure. The total selenium content was determined fluorometrically following after the method of Watkinson (1966) with 2,3- diaminonaphtalene using the Hitachi F-2000 spectrofluorometer. All analyses were performed on triplicate samples. The statistical analysis was performed using the Statistica software at the level of significance of 0,05. 2

3 Table 1. Some general properties and total and DTPA- extractable selenium content in the investigated soils. Horizon Thickness [cm] Depth of sampling [cm] Percentage of soil fractions <0,02 <0,002 mm mm Texture by USDA* ph in H 2 O ph in KCl Organic matter [%] Se-DTPA [mg. kg -1 ] Se-total [mg. kg -1 ] Se- DTPA Se-total [%] Black earths Profile N o fsl fsl A fsl fsl fsl fsl ABbrg fsl Profile N o fsl A fsl fsl ABbr scl Cca < sl Typical brown soils Profile N o fls fls A fls fls fls ABbr fsl Bbr sl

4 Table 1. continued Profile N o fls A fls fls fls ABbr fls Bbr scl Lessivé soil Profile N o ls Ap sl Eet/Bt sl Bt <45 < sl Profile N o sl Ap sl Bt sl Profile N o sl Ap sl Eet ls Bt sl Profile N o ls Ap ls Eet sl Eet/Bt sl Profile N o sl Ap sl Eet ls Eet/Bt ls Bt <55 < ls

5 Results and discussion General properties of the soils under study are given in Table 1. The investigated Kujawy black earths had a texture of fine sandy loam and sandy clay loam ( the silt and clay content was 20-36%). In general, the brown soils demonstrated of fine loamy sand and fine sandy loam (the silt and clay content was 10-32%), while lessivé soil had a texture of sandy loam and loamy sand (the clay fraction <0.002 mm ranged 3-17%). The ph values of both soils were neutral to slightly acidic. The soils differed in the organic matter content: the organic matter content in the humus horizon (A) of the Kujawy black earths ranged %, while the upper horizons contained less organic matter ranging from 0.28 to 0.57%. The organic matter content of the A horizon of brown soils was in the range % and % in the upper horizons. Organic matter content in the Ap horizon of lessivé soil ranged from 0.56 to 1.11% and from 0.02 to 0.27% in the upper horizons. The total selenium content in the humus horizons (A) of the Kujawy black earths was from to mg kg -1 (mean mg kg -1 ), while in the horizons ABbr and Cca fluctuated it was mg kg -1 and mg kg -1, respectively. Typical brown soils were characterized by the total selenium content in the humus horizon of mg kg -1. The average total selenium content in the horizon ABbr and the cambic horizon of brown soils was mg kg -1 and mg kg -1, respectively. The amounts of total selenium in humus horizon of investigated lessivé soil ranged from to mg kg -1 (mean mg kg -1 ). The total selenium content content (mean value mg kg -1 ) the in luvic horizon decreased slightly, while in the Eet/Bt horizon of lessivé soil ranged mg kg -1 (mean mg kg -1 ), and that in the argillic horizon was lower (mean mg kg -1 ). The comparison of the obtained results with earlier studies and the findings of other authors (Borowska et al.,1994; Borowska, 1995; Kabata-Pendias & Pendias, 1993; Zab³ocki, 1994) indicated that the analysed soils were poor in this microelement. According to Kabata-Pendias & Pendias (1993) the average selenium content in the surface horizons of the soils the world is 0.33 mg kg -1, and the range of most frequent average values is mg kg -1. The distribution of total selenium content in the genetic horizons of the investigated soils was similar to the data reported by Zab³ocki (1994) for soils of the Pomorze Zachodnie and by Kabata-Pendias & Pendias (1984) for some profiles of New Zealand soils. Horváth et al. (1996) have shown that in the Hungarian soil profiles the average value of selenium content decreased with increasing depth. Generally, total selenium is higher in soils with high organic matter content (Wu & Lag, 1988; Hamdy & Gissel-Nielsen, 1976). However, there was no statistical correlation between the total selenium content in the investigated soils and the content of organic matter. The content of total selenium in the Eet and Eet/Bt horizons of Luvisols under study was statistically correlated with the content of clay fraction (r=0,89**). 5

6 To define potential selenium availability for plants its DTPA extractable forms were determined and compared with total selenium content in the genetic horizons of chosen soil pedons. As results from Table 1. the average DTPA-extractable selenium content in the humus horizon of black earths was mg kg -1. ABbr and Cca were particulary rich in DTPA-extractable selenium demonstrated the average content of mg kg -1. Typical brown soils in the humus horizon characterized by the Se-DTPA content of mg kg -1 (mean mg kg -1 ). In the transitional (ABbr) and cambic horizons a higher level of Se-DTPA ( mg kg -1 ) was detected. The content of Se- DTPA in the humus horizon of lessivé soil was within the range mg kg -1, whereas Eet/Bt and argillic horizons contained higher amounts of Se-DTPA (mean mg kg -1 ). Statistical analysis shown a significant correlation between total and DTPAextractable selenium (0,68**) in the humus horizon of the investigated black earths (Fig.1). Figure 1. Correlation between total and DTPA-extractable selenium of black earths. The percentage of DTPA-extractable forms of selenium in the total selenium content ranged from 1.77% (in humus horizon) to 6.11% (in ABbr and Cca horizons) of Kujawy black earths. The content of Se-DTPA in the total selenium in typical brown soils was 1.79% in the A, 2.82% in the ABbr and 2.60% in the Bbr horizons. The contribution of Se-DTPA in total selenium of Luvisols increased with the depth of sampling and was: 0.75% in Ap horizon, 1.44% in the Eet horizon, 2.27% in the Eet/Bt horizon and 2.6% in the Bt horizon. Those results corresponded with the findings of other authors (Zab³ocki, 1994; Kang et al.,1990). It should be underline, that the 6

7 participation of DTPA-extractable forms of selenium in the total selenium content of investigated soils ranged % what indicated its low mobility and availability to plants. References Borowska K.(1995): In: 15.Arbeitsagung Mengen- und Spurenelemente,Friedrich- Schiller- Universität, Jena, Borowska K., Malczyk P., Kêdzia W. (1994): Zesz.Nauk.Komitetu Cz³owiek i Œrodowisko PAN, 8,33-37 Cieœla W. (1968): Rocz.WSR Poznañ, 18, 1-60 Cieœla W., D¹bkowska-Naskrêt H., D³ugosz J., Zalewski W. (1994) Soil Sci. Ann., Suppl.XLIV,79-84 Hamdy A.A., Gissel-Nielsen G.(1976): Riso Report No 349, Denmark Horváth E., Pantó Gy, Wieszt Z., (1996): Proc.III Int.Symp. Selenium in Geochemistry, Biology and Medicine, Belgrade, 3-5 Nov. Kabata-Pendias A., Pendias H. (1984): In: Trace elements in soils and plants. CRC Press, Inc.Boca Raton, Florida Kabata-Pendias A., Pendias H. (1993): In: Biogeochemistry of trace elements. (In Polish), PWN, Warszawa Kang Y., Yamada H., Kyuma K., Hattori T.(1990): Soil Sci.Plant Nutr.36,(3), Lindsay W.L., Norvell W.A. (1978): Soil Sci.Soc.Am.J., 42, Watkinson (1966): Anal.Chem. 38, Wu L., Lag J.(1988): Acta Agric. Scan., 38, Key words: total selenium, DTPA-extractable selenium, soil, Poland Mots clés : Se total, Se extractible à DTPA, Se, sol, Pologne 7