Scientific registration n o : 1734 Symposium n o : 40 Presentation : poster. ALVES William, MELO Wanderley, FERREIRA Manoel

Transcription

1 Scientific registration n o : 1734 Symposium n o : 40 Presentation : poster Urban solid waste compost application in sandy soil: micronutrients and heavy metals in the soil and plants Epandage de compost d ordures ménagères en sol sableux : oligoéléments et métaux lourds dans le sol et les plantes ALVES William, MELO Wanderley, FERREIRA Manoel FCAV/UNESP Departamento de solos e adubos, Rodovia Carlos Tonnani, km5, Jaboticabal, São Paulo, Brasil. INTRODUCTION Composting is the exothermic aerobic bioxidation of a heterogeneous organic substratum, in the solid state, characterized by the production of CO 2 and water, liberation of mineral substances and formation of stable organic matter (Zucconi & Bertoldi, quoted by Fernandes et al., 1993). The product of the composting, well-known as organic compost, is a homogeneous material, biostabilized, having dark coloration, C/N ratio around 10/1, nutrients contents depending on processed material and free from pathogenic microorganisms witch were destroyed by the high temperatures in the process. Its utilization in the agriculture has presented great interest in the improvement of the physical, chemical and biological properties of the soil (Kiehl, 1985; Nakagawa, 1992). According to Grossi (1993), when the garbage is used as substratum for compost production it contains several pollutants as glasses, plastics and metals, that may harm the quality of the product. These materials may elevate the amount of some pollutants in the compost, for instance, of the heavy metals, which are harmful to the environment and, consequently, to the mankind. The fact that the metals are present in the soil does not mean that it will be assimilated by plants, for it could stay for long periods in the soil without being absorbed. It is the bioavailability of the metals that really affects the environment where these elements are found. According to Egreja Filho (1993), studies have demonstrated that there is no correlation between the total content of heavy metals in the soil and its fitotoxicity. In soils fertilized with urban waste compost, the bioavailability of the metals depends on factors such as concentration in the compost, application rate and soil type where the content and clay type, ph and CEC are factors directly associated. As for the absorption of heavy metals by plants, it may frequently occur accumulation of considerable amounts in the vegetable tissues, even exceeding the 1

2 human and animal organisms tolerance levels, without harming the production or causing visible fitotoxic effects (Haan, 1981). The aim of this experiment was to evaluate the total and available content of micronutrients and heavy metals in soil fertilized by urban waste compost and the accumulation of these elements by sorghum plants. MATERIAL AND METHODS The experiment was carried out at green house of the former CETESB (Companhia de Tecnologia de Saneamento Ambiental) experimental station in Novo Horizonte - SP. The soil utilized was a sandy Podzolico Vermelho Amarelo, collected from the layer of 0 to 20cm of depth. The chemical analysis according to methodology described in Raij et al. (1987) presented the following results: P(resin)=2mg dm -3, O.M=13g dm -3, ph in CaCl 2 =4.6, K=2.3mmolc dm -3, Ca=15mmolc dm -3, Mg=3mmolc dm -3, H+Al=28mmolc dm -3, CEC=48mmolc dm -3 and exchangeble cations saturation = 42%. The determination of total content of micronutrients and heavy metals in soil, according to methodology described in Baker & Amacher (1982), presented the following results in mg kg -1 : Cu=7, Zn=10, Mn=62, Fe=13650, Cr=37, Ni, Cd and Pb = not detected. A factorial 2x5 scheme was utilized, with 4 repetitions in randomized scheme, adding up 40 pots. The treatments were constituted by the combination of two factors: chemical fertilization (presence and absence) and compost (in the rates 0, 12.5, 25, 50 and 100 t ha -1 ) in dry basis. The chemical fertilization (nutrient solution) contained the elements N, P, K, S, B, Fe, Mn, Mo and Zn. The compost was obtained in the urban waste facility of CETESB, in Novo Horizonte (SP). In order to determine the macronutrients, total organic matter and ph, Kiehl (1985) methodology was used and the following results were obtained: ph = 8.1, N=6.7g kg -1, P=5g kg -1, K=67mg kg -1, Ca=358mg kg -1, Mg=31mg kg -1, O.M=300mg kg -1 and C/N ratio=12/1. According to Baker & Amacher (1982) chemical analysis of the compost, for micronutrients and heavy metals, presented the following results: Cu=130 mg kg -1, Zn=310mg kg -1, Mn=234mg kg -1, Fe=27100mg kg -1, Pb=172mg kg -1, Cr=108mg kg -1, Ni=12mg kg -1 and Cd = not detected. The soil and the compost were dried and sifted in 4mm sieve before they were used. For installation of the experiment were utilized 5,3dm 3 plastic pots. Dolomitic calcareous was utilized to lime the soil and to add it in order to elevate the saturation bases at 70%. The mixtures of soil and compost were made according to the treatments and they were placed in the pots. Deionized water was added in enough amount to elevate the soil at 70% of the field capacity. Afterwards it was incubated during 40 days. Finally, it was sowed 5 sorghum seeds (Sorghum bicolor) in the depth of 1 cm, leaving 1 seedling 20 days later. The experiment was carried out during 97 days after sowing, when it was harvested, and the plants were cut close to the soil. After appropriately washing and drying, the dry matter of roots and edible parts were analyzed for the content of the Fe, Mn, Zn, Pb, Cr and Ni (Baker & Amacher, 1982). After harvest a soil sample was obtained for each pot which was analyzed for total content of Pb, Cr, Ni, Zn, Cu, Fe and Mn (Baker & Amacher, 1982). The available content of the same elements was obtained through extraction by DTPA (Lindsay & Norwell, 1978). 2

3 Achieved data were submitted to ANOVA in factorial scheme and the effects of rates of compost were isolated in regression analysis. RESULTS AND DISCUSSION The total contents of Cu, Zn, Mn, Fe, Cr, Pb and Ni in the soil are presented at the Table 1. The contents of Cu, Zn, Mn and Fe increased in both the absence (A 0 ) and the presence (A 1 ) of chemical fertilization due to the compost application. Furthermore, the greatest increments were observed for Cu and Zn. For these elements, Purves & Mackenzie (1973) observed an increase in the soil content up to excessive levels using 100 t ha -1 of urban compost. Table1: Total content of micronutrients and heavy metals in the soil, due to compost (C) application, in the absence (A 0 ) and presence (A 1 ) of chemical fertilization. Compost Cu Zn Mn Fe Cr Pb Ni t ha -1 mg kg -1 Chemical fertilization absence Chemical fertilization presence F A 4.6* 3.3* 113.2** 12.9** 0.5 NS 14.2** 49.4** C 40.5** 8.5** 11.1** 8.1** 2.2 NS 0.7 NS 6.6** AXC 6.0** 0.6 NS 2.7 NS 2.2 NS 0.5 NS 1.2 NS 2.9* CV(%) Four repetitions mean; NS, *, ** Not significant, P < 0,0 5 and P < 0,01 respectively. A = chemical fertilization factor. The Zn, Mn and Fe contents were greater in the presence of chemical fertilization because these elements were part of the nutrient solution utilized. The soil content of Cu, which was not utilized in the chemical fertilization, was similar in A 0 and A 1. According to Environmental Protection Agency (1983), several authors quoted by Egreja Filho (1993) and Malavolta et al. (1991) data, it is verified that in spite of the significant increases of Cu, Zn, Mn and Fe total contents in soil (confirmed by not presented regression analyses) its levels stay in an appropriate pattern. In this case, the compost acts like a micronutrients supplier. In the case of Zn the tolerable maximum limit in the soil (50 mg kg -1 ) will be reached after 3 or 4 years of serial applications of compost in the rate of 100 t ha -1 and in the case of the other micronutrients the limits may be reached with some years of applications. In order to prevent the contamination of the soil, it is important to monitor the micronutrients and heavy metals contents in the compost and application rates. 3

4 Compost rates did not affect the Cr and Pb total contents in the soil in the absence or presence of chemical fertilization. The total content of Ni in A 0 increased lineally (y= x, r 2 =0.95) due to compost rates and in A 1 it was not affected. The content of Cr in the soil was not affected by chemical fertilization, and Pb and Ni presented greater concentration in its absence. The observed contents of Cr and Ni are in the normal range considered to soils 100 and 40 mg kg -1 respectively (Egreja Filho, 1993). The values found to Pb were above the 10 mg kg -1 mentioned by the same author as normal level. Based on normal levels for Cr, Pb and Ni in the soil, even in an application of 100 t ha -1 of compost should not cause problems. However, successive applications may elevate the metals content to toxic levels for the plants. In the specific case Pb, whose concentration in the compost is 172 mg kg -1, each application of 100 t ha -1 of conpost, (considering the layer of 20 cm of depth), corresponds to an increase of about 8.6mg dm -3 of Pb. The micronutrients and available heavy metals contents, evaluated by extraction with DTPA, are presented at the Table 2. Having been used in the chemical fertilization, Zn, Mn and Fe presented greater available content in the presence rather than in the absence of chemical fertilization. On the other hand, Cu which did not make part of the chemical fertilization, had a similar content in both A 1 and A 0. Cu and Zn had its available content correlated lineally and positively with the rates of compost, even in A 0 and A 1 (r 2 =0.99 for the two elements in the two conditions). Compost rates just affected Mn and Fe contents in A 1 (negative correlation). It means that the decrease of the levels of these two elements occurred due to the elevation in the rate of compost. In A 0 the contents of Mn and Fe were not affected for the compost rate. Increase in the availability of Cu, Zn and also Ni extracted by DTPA was observed by Street et al. and Schauer et al., mentioned by Petruzzelli (1989), as effect of the application of sewage sludge to the soil. A possible explanation for the fact that Mn and Fe have its available contents decreased in the presence of chemical fertilization and not affected in the absence - differing from behavior of Zn and Cu contents due to the compost rates - may be the fact of Fe 2+ and mainly Mn 2+ form very stable complexes with the organic matter causing a decrease in its availability (Borkert, 1991). The decrease in the Fe and Mn availability was probably accentuated in A 1 by the greatest contents of this elements in this case. On the other hand in A 0, due to the smallest amounts of those micronutrients, the effect of the complexation by organic matter was not so obvious. In the case of Pb and Ni, there was an elevation of its available contents due to compost rates in the absence and in the presence of chemical fertilization. Nevertheless, the available contents are much smaller than the totals. Data of the Tables 1 and 2 show that the increase in the total content of the micronutrients just produced available content increase to Cu and Zn. The micronutrients contents in the edible parts and roots of sorghum can be observed at the Table 3. 4

5 Table 2: Available contents of micronutrients and heavy metals in the soil, due to compost (C) addition, in the absence (A 0 ) and presence (A 1 ) of chemical fertilization. Compost Cu Zn Mn Fe Pb Ni t ha -1 mg kg -1 Chemical fertilization absence Chemical fertilization presence F A 0.7 NS ** ** ** ** 11.3 ** C ** ** 87.9 ** 16.7 ** 81.7 ** 48.2 ** AXC 0.7 NS 1.9 NS 65.8 ** 19.5 ** 9.3 ** 5.1 ** CV(%) Four repetitions mean; NS, *, ** Not significant, P < 0,0 5 and P < 0,01 respectively. A = chemical fertilization factor. The contents of Zn, Mn and Fe in the roots and edible parts were greater in A 1 because of the chemical fertilization utilized. For these 3 micronutrients, there was positive correlation between content and compost rates in A 0, but the correlation was positive for Zn and negative for Fe and Mn in A 1. In A 0 : y = x r 2 = 0.89 for Zn; y = x r 2 = 0.91 for Mn; y = x r 2 = 0.98 for Fe; In A 1 : y = x r 2 = 0.99 for Zn; y = x r 2 = 0.85 for Mn; y = x r 2 = 0.86 for Fe. In the case of Fe, there was not effect of compost rates in the presence of chemical fertilization on the roots contents. These data are related to those obtained in soil for the available contents of Zn, Mn and Fe, in other words, in the soil there were decrease of the available Fe and Mn and increase in the available Zn, which means that the plants absorbed more Zn and less Fe and Mn. Trinidad et al. (1996) obtained similar results in his experiment, and verified smaller absorption of Mn for the plants fertilized with urban waste compost, at the same time that the total content of this element in the soil had increased, which shows that the relationship between content in the soil and plant should be done in element available content basis and not in total basis. 5

6 Table 3: Micronutrients contents in roots and edible parts of sorghum, due to compost (C) addition, in the absence (A 0 ) and presence (A 1 ) of chemical fertilization. Edible parts Roots Compost Zn Mn Fe Zn Mn Fe t ha -1 mg/plant Chemical fertilization absence Chemical fertilization presence F A 316.0** 579.7** 146.5** 251.2** 157.0** 39.4** C 14.1** 6.5** 0.5 NS 26.74** 1.5 NS 3.3* AXC 1.69 NS 9.64** 7.51** 0.25 NS 8.1** 4.8** CV(%) Four repetitions mean; NS, *, ** Not significant, P < 0,0 5 and P < 0,01 respectively. A = chemical fertilization factor. For micronutrients in the plants tissues Dechen et al. (1991) mention that the variation in its content is big and it may be influenced by several factors. When the range of considered normal tissues contents Zn=20 to 50mg kg -1, Mn=10 to 20mg kg -1 and Fe=100mg kg -1 (Dechen et al., 1991), is compared with the achieved data (transformed to mg kg -1 ) it may be verified that, except for Zn in A 0, the micronutrients contents were more elevated in the plants tissues than mentioned for those authors. Studying application of urban waste compost rates (0, 8, 16, 32 and 64 t ha -1 ) in sorghum cultivated in sandy soil, Hortenstine & Rothwell (1973) obtained similar results. Moreover, they obtained respectively for Mn 0.65, 1.18, 2.11, 2.59 and 5.06mg plant -1 and for Zn 0.33, 0.84, 1.61, 2.40 and 4.91mg plant -1. According to the mentioned authors even in the highest rates, fitotoxic effects attributable to the micronutrients did not occur. Cr, Pb and Ni were not detected in the roots or edible parts of the plants in both A 0 and A 1, even in the elevated rate of compost. CONCLUSIONS In a nutshell, the application of 100 t ha -1 of urban waste compost to sorghum plants does not cause heavy metals fitotoxicity or micronutrients excess. However, it should be observed that positive correlation occurs between compost rates and some micronutrients and heavy metals contents. Therefore, successive applications of compost may lead to a fitotoxicity situation due to the accumulation of micronutrients and/or heavy metals in the soil. 6

7 ACKNOWLEDGEMENTS Thanks to FAPESP (Fundação de Amparo a Pesquisa do Estado de São Paulo) for financial support. REFERENCES BAKER, D.E., AMACHER, M.L. Nickel, copper, zinc and cadmium. In: PAGE, et al. ed. Methods of soil analysis. part ed. American Society of Agronomy, p BORKERT, C.M. Manganês. In: Simpósio sobre Micronutrientes na Agricultura, 1. Piracicaba, POTAFOS/CNPq, p DECHEN, A.R.; HAAG, H.P. & CARMELLO, Q.A. de Diagnose visual In: Ferreira, M.E. & Pessoa da Cruz, M.C., ed. Micronutrientes na Agricultura. Anais 1 o Simpósio sobre micronutrientes na Agricultura. Piracicaba, POTAFOS/CNPq, p EGREJA FILHO, F.B. Avaliação da ocorrência e distribuição química de metais pesados na compostagem do lixo domiciliar urbano. Viçosa: UFV, p. (tese de mestrado). ENVIRONMENTAL PROTECTION AGENCY - Land application of municipal sludge. Cincinnati, october, FERNANDES, F., PIERRO, A.C., YAMAMOTO, R.Y. Produção de fertilizante orgânico por compostagem do lodo gerado por estações de tratamento de esgotos. Pesq. Agropec. bras., Brasilia, 28(5): , GROSSI, M.G. de L. Avaliação da qualidade dos produtos obtidos de usinas de compostagem brasileiras de lixo doméstico através de determinação de metais pesados e substâncias orgânicas tóxicas. São Paulo, USP, p. Tese (Doutorado). HAAN, S. Results of municipal waste compost research over more than fifty years at the institute for soil fertility at Haren/Groningen, the Netherlands. Neth. J. Agric. Sci., 29:49-61, HORTENSTINE, C.C. & ROTHWELL, D.F. Pelletized municipal refuse compost as a soil amendment and nutrient source for sorghum. J. Environ. Qual. 2(3): , KIEHL, E.J. Fertilizantes orgânicos. Piracicaba, CERES, p. LINDSAY, W.L. & NORWELL, W.A. Development of a DTPA soil test for zinc, iron, manganese and copper. Soil Sci. Soc. Am. J., 42: , MALAVOLTA, E.; BOARETO, A.E. & PAULINO, V.T. Micronutrientes, uma visão geral visual In: Ferreira, M.E. & Cruz, M.C.P, ed. Micronutrientes na Agricultura. Anais 1 o Simpósio sobre micronutrientes na Agricultura. Piracicaba, POTAFOS/CNPq, p NAKAGAWA, J. Compostagem: obtenção e uso. In: GUERRINI, I.E. ed. Encontro sobre matéria orgânica do solo - problemas e soluções. Botucatu, p PETRUZZELLI, G. Recycling wastes in agriculture: heavy metal bioavailability. Agric., Ecosys. and Environ., 27: , PURVES, D., MACKENZIE, J.E. Effects of applications of municipal compost on uptake of copper, zinc and boron by garden vegetables. Plant and soil, 39: , RAIJ, B. van; QUAGGIO, J.A.; CANTARELLA, H.; FERREIRA, M.E.; LOPES, A.S. & BATAGLIA, O.C. Análise química do solo para fins de fertilidade. Campinas, Fundação Cargill, p. TRINDADE, A.V.; VILDOSO, C.I.A.; MUCHOVEJ, R.M.C. & COSTA, L.M. Interação de composto de lixo urbano e fungos micorrízicos na nutrição e crescimento do milho. R. bras. Ci. Solo, Campinas, 20: , Keywords: urban waste, compost, heavy metal, micronutrients Mots clés : ordure ménagère, compost, métaux lourds, oligoéléments 7