Scientific registration n o : 2303 Symposium : 25 Presentation : poster

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1 Scientific registration n o : 2303 Symposium : 25 Presentation : poster Evaluation of nutrients availability and metals toxicity by different universal extractants in brazilian soils 1 Evaluation de la disponibilité des nutriments et de la toxicité de métaux dans les sols du Brésil à l aide de différents types d extraction 1 ABREU JUNIOR Cassio H. (2,3), MURAOKA Takashi (3), GINÉ Maria F(3) (1) Work with financial support of FAPESP (2) Graduate Student, ESALQ-USP, Brazil, cahabreu@carpa.ciagri.usp.br (3) CENA-USP, Caixa postal 96, Piracicaba, SP, Brazil, CEP Introduction The term universal soil extractant has been used to name reagents or procedure to evaluate several elements, and/or ions from a soil to find out the soil fertility status and/or metal toxicity (Jones Jr., 1990). Among universal extractants used worldwide for these purposes, the first one was the Morgan Extractant (sodium acetate buffered at ph 4.8) which was modified later by Wolf (1982) with the addition of DTPA to improve micronutrients extraction, and called as Wolf-Morgan extractant. Many others are also being used elsewhere, such as Mehlich-1 (Jones Jr., 1990), Mehlich-3 (Mehlich, 1984), AB-DTPA (Soltanpour and Swab, 1977), DTPA (Lindsay and Norvell, 1978) and ion exchange resin (Raij et al., 1986). Ion exchange resin, for determining P, K, Ca, and Mg, and DTPA, for determining Cu, Fe, Mn, and Zn, are the most used soil macronutrient and micronutrient extractants, respectively, in the State of São Paulo, Brazil. The use of urban waste compost in agriculture has brought up the risk of soil and plant contamination (Petruzzelli, 1989), becoming important to determine possible metals toxicity. The main question with application of urban waste compost to agricultural soils is the presence of Cd, Cr, Cu, Ni, Pb and Zn in waste material at a considerable concentration, which may accumulated in the soil upper layer and be toxic to plants or, if they go into the food chain, be harmful to animals and humans. Therefore, it is important to check the concentration of metallic elements in soil to avoid their accumulation. In this study we evaluated the capability of resin ion exchange, DTPA, Mehlich-1 (M-1), Mehlich-3 (M-3), and Wolf-Morgan (W-M) extractants for determining nutrients availability and metals toxicity in different Brazilian soils treated with urban waste compost from the city of São Paulo. Material and methods The urban waste compost was collected at São Matheus Treatment Plant, in the city of São Paulo. The compost was air dried and passed through a 4 mm mesh. Some 1

2 compost characteristic are: total organic C g kg -1, total N 12.8 g kg -1, and C/N ratio The soils, twenty one acid, four calcareous, and one alluvial saline-sodic soils (varying among Oxisol, Ultisol, Alfisol, Acrisol, Alisol, Quartzipsamment, Aquox, and Fluvent by Soil Taxonomy classification, or Ferralsol, Nitisol, Lixisol, Luvisol, Arenosol, Gleysol, and Fluvisol by FAO/UNESCO legend) were obtained from different States of Brazil, and collected from the surface horizon. Some soils characteristic are: ph (CaCl 2 ) 3.8 to 7.9, organic C 7.1 to 27.9 g dm -3, total N 0.47 to 2.78 mg dm -3, P 1.4 to 46.5 mg dm -3, and concentration of Ca, Mg, K, and H+Al, in mmol c dm -3, ranged from 1.2 to 412, 1.1 to 40.6, 0.70 to 13.84, and 7.95 to , respectively. The greenhouse study was carried out in pots containing 1.1 dm 3 of each soil. Compost (at rate of 60 t ha -1 or 30 g dm -3 ) was applied sole, with mineral fertilizer, with lime, or with lime plus fertilizer. A control and lime plus fertilizer treatments were also included. Each pot was considered as a plot, and plots were arranged in a randomized complete block design with split plots (soil as main plot), with 3 replications. Dolomitic lime was applied one month prior to the compost incorporation, at the rate necessary to increase soil base saturation to 70 %. Mineral fertilizer was applied at the same time as compost. Soil samples, approximately 130 cm 3, were taken after one month of compost incubation. Rice seeds were then sown and seven plants per pots were grown for two months, when they were harvested for analysis. Nutrients and metals in soils were extracted by ion exchange resin (Raij et al., 1986), DTPA (Lindsay and Norvell, 1978), Wolf-Morgan (Wolf, 1982), Mehlich-1 (Jones Jr., 1990), and Mehlich-3 (Mehlich, 1984). Plant extract was obtained by HNO 3 - HClO 4 digestion. All extracts obtained were analyzed by inductively-coupled plasma atomic emission spectrometry (ICP-AES) for determining Ca, Mg, P, B, Cu, Fe, Mn, Mo, Zn, Ba, Cd, Co, Cr, Ni, Pb, Sr, Ti, and V, and by flame photometry for K and Na. Results and discussion The range of concentration of macro and micronutrients obtained by different universal soil extractants are presented in Table 1. For all extractants, the concentrations of K, Ca, Mg and Na, in mmol c dm -3, ranged from 0.62 to 27.84, 0.44 to , 0.13 to 65.73, and 0.05 to 28,16, respectively. The concentrations of P, B, Cu, Fe, Mn, Mo, Ni, and Zn, in mg dm -3, ranged from 0.26 to , 0 to 3.45, 0 to 26.53, 0 to , 0.87 to , 0 to 7.34, 0 to 13.36, and 0.01 to 55.41, respectively. The following ranges of Ba, Cd, Co, Cr, Pb, Sr, Ti, and V, in mg dm -3, were also observed: 0 to 108.1, 0 to 1.25, 0 to 6.86, 0 to 2.27, 0 to 12.1, 0 to 44, 0 to 8.54, and 0 to 13.87, respectively. In average, M-3 extracted higher contents of K, Ca, Mg, Na, B, Cu, Fe, Mn, Mo, Zn, Co, Pb and Ti. Extractability of P, Ni, Ba, Cd, Cr, and V was greater by resin, but close to that obtained by M-3, mainly for P and Cr. Usually, DTPA and W-M resulted in lower ranges for the most of the elements. Very high positive correlations (p<0.001, data not shown) were found for K, Ca, and Mg extracted by resin and with that obtained by either M-3, M-1 or W-M. Resin-P correlated better with M-3 and M-1 P than with W-M. Very strong correlations (p<0.01, data not shown) were also observed for all micronutrients and metal extracted by DTPA with those by either M-3 or W-M, followed by M-1, but low by resin. The concentration ranges of K, Ca, Mg and P extracted by M- 1 and M-3 reported by Gascho et. al. (1990) were much lower than those in this paper. It seems that at low cation concentrations, cations extracted by M-1 and M-3 were 2

3 similar, but at higher concentrations, as in the present study, where compost increased the sum of bases, Ca, Mg, K and Na extractability was higher by M-3 than M-1, and quite similar for P. Evaluation of Cr, Cd, Ni and Pb in 31 non-contaminated soils from the State of Sao Paulo (Brazil) by DTPA, M-1, and M-3 (Abreu et al., 1995) showed comparable values to those obtained in this work, but wider concentration ranges were observed here. K, P, Cu, Mn, Ba (M-1 not included) and Sr taken up by rice plants correlated significantly (p<0.05) with all extractants, when all soil and acid soil were included in the data set (Table 2 and 3). Correlation between plant Ca and B with that extracted by all extractants were significant (p<0.01) only for acid soils. Plant Mg was also positively correlated (p<0.05) with all extractants for acid soil, but for alkaline soils, which had extremely high levels of exchangeable bases, negative correlation were found (r = * to * ). M-1, M-3 and W-M extracted Cr had the same behavior, positive correlation for acid and negative for alkaline soils. Correlation between plant Na and that extracted both by M-1 and M-3 were significant (p<0.01) for all, acid and alkaline soils data. Concentration of Fe, Zn and Cd for all extractants, except for the resin, were positively correlated with those taken up by rice plants for all and acid soils. Extracted Mo, Co, Ni, Pb, Ti and V were less correlated with their plant contents. For P, in accordance with Raij et. al. (1986), the results obtained with the different extractants presented substantial differences, and usually were poorly correlated with P taken up by plants. Ion exchange resin are being used as the official method of soil analysis in the State of São Paulo, due to stronger correlation observed between resin and P taken up by plants than the others. In this work, M-1 and M-3 presented similar or even higher correlation with extractable and plant P. This was probably due to ICP-AES determination which gives higher values than the colorimetric analysis as it has the capability of determining also the organic P present in the extracts (Soltanpour et. al., 1979). A disadvantage of resin method (0.8 N NH 4 Cl in 0.2 N HCl as final extract), is it troublesomeness during ICP- AES determination, clogging the sample delivery capillary tube with precipitated ammonium salts. For non-contaminated soils of São Paulo, M-1, M-3 and DTPA extractants were considered by Abreu et al. (1995) ineffective to evaluate Cd, Cr, Ni, and Pb availability for wheat, and Cd and Pb for bean plants because of the poor correlation with plant uptake and soil content, but this effect was attributed to the low metal concentration in those soils. Our conclusion is that Mehlich-3 extractant seems to be adequate both to evaluate nutrient availability and elemental toxicity, while DTPA seems to be useful not only for Cu, Fe, Mn and Zn, but also for some metals. The use of ICP-AES for determining multi-elemental concentration in soil extracts are very helpful and less timeconsuming. References Abreu, M.F.; Raij, B.V.; Santos, W.R Comparação de métodos de análise para avaliar a disponibilidade de metais pesados em solos. R. bras. Ci. Solo. 19: Gascho, G.J.; Gaines, T.P.; and Plank, C.O Comparison of extractants for testing coastal plains soils. Commun. Soil Sci. Plant Anal. 21: Lindsay, W.L.; Norvell, W.A Development of a DTPA soil test for zinc, iron, manganese, and copper. Soil Sci. Soc. Am. J. 42:

4 Mehlich, A Mehlich 3 soil extractant: a modification of Mehlich 2 extractant. Commun. Soil Sci. Plant Anal. 15: Petruzzelli, G Recycling wastes in agriculture. Heavy metal bioavailability. Agric. Ecos. Env..27: Raij, B.V.; Quaggio, J.A.; and Silva, N.M Extraction of phosphorus, potassium, calcium, and magnesium from soil by an ion exchange procedure. Commun. Soil Sci. Plant Anal. 17: Soltanpour, P.N.; Schwab, A.P A new soil test for simultaneous extraction of macro- and micro-nutrients in alkaline soils. Commun. Soil Sci. Plant Anal. 8: Soltanpour, P.N.; Workman, S.M.; Schwab, A.P Use of inductively coupled plasma spectrometry for the simultaneous determination of macro and micronutrients in ammonium bicarbonate-dtpa extracts of soils. Soil Sci. Soc. Am. J. 43: Wolf, B An improved universal extracting solution and its use for diagnosing soil fertility. Commun. Soil Sci. Plant Anal. 13: Key words: universal extractant, soil testing, nutrient availability, metal toxicity, urban waste compost Mots clés: extracteur universel, analyse des sols, disponibilité des nutriments, toxicité des métaux, compost urbain 4

5 Table 1. Minimum, medium and maximum concentrations of nutrients and metals obtained by some universal extractants in different Brazilian soils (N = 156). K Ca Mg Na P B Cu Fe Mn Mo Ni Zn Ba Cd Co Cr Pb Sr Ti V mmol c dm mg dm Resin ND DTPA ND ND ND Mehlich ND Mehlich Wolf-Morgan ND ND - Not determined - Minimum concentration - Medium concentration - Maximum concentration 5

6 Table 2. Correlation coefficients among nutrients uptake by rice and those obtained by different soil extractant. Soil extractant K Ca Mg P B Cu Fe Mn Mo Ni Zn All soils (N=156) Resin DTPA ND ND Mehlich Mehlich Wolf-Morgan Acid soils (N = 126) Resin DTPA ND ND ** Mehlich Mehlich Wolf-Morgan Alkaline soils (N=30) Resin DTPA ND ND Mehlich Mehlich Wolf-Morgan * Significant at 5 % level ** Significant at 1 % level ND Not determined 6

7 Table 3. Correlation coefficients among some metals uptake by rice and those obtained by different soil extractant. Soil extractant Ba Cd Co Cr Na Pb Sr Ti V All soils (N=156) Resin ND DTPA ND Mehlich-1 ND Mehlich Wolf-Morgan ND Acid soils (N = 126) Resin ND DTPA ND Mehlich-1 ND Mehlich Wolf-Morgan ND Alkaline soils (N=30) Resin ND DTPA ND Mehlich-1 ND Mehlich Wolf-Morgan ND * Significant at 5 % level ** Significant at 1 % level ND Not determined 7