RESUMO O uso agrícola de lodo de esgoto e derivados no Estado de São Paulo é regulamentado por norma federal e por norma paulista, que recomendam que esses materiais quando incorporados a solos agrícolas devem apresentar no mínimo 30 % de degradação do carbono total. Para observar as frações de degradação de um lodo de esgoto e de um composto, produzido a partir do mesmo lodo juntamente com poda de árvore urbana triturada, realizaram-se dois ensaios de biodegradação de C. As doses dos resíduos foram adicionadas em frascos contendo 500 g de solo coletado na profundidade de 0,00-0,20 m de um Nitossolo Háplico Álico textura argilosa. No ensaio I, as doses de lodo (L) e composto (C) utilizadas consideraram percentuais da necessidade em N para a cultura da cana-de-açúcar, e expressas em Mg ha-1 de resíduo (base úmida): L1 21,2 (100 %); L2 42,4 (200 %); C1 69,4 (50 %); C2 138,9 (100 %); e C3 277,8 (200 %). O ensaio II foi realizado apenas com o lodo de esgoto, utilizando-se doses 5, 10, 15 e 20 vezes maiores que aquelas recomendadas no ensaio I: L3 120; L4 240; L5 360; e L6 480, simulando sucessivas aplicações do resíduo no solo. O C-CO2liberado foi quantificado por meio da medida de condutividade elétrica. O lodo de esgoto no ensaio I apresentou menores frações de degradação quando comparado ao composto orgânico, mas a taxa de decomposição do composto foi menor, provavelmente pela presença de substâncias recalcitrantes resultantes do processo de humificação. A fração de degradação dos resíduos no solo atingiu valor próximo a 30 % apenas para a dose de lodo de esgoto 20 vezes superior à dose exigida pela cultura, e assim não poderiam ser utilizados em solos agrícolas argilosos. Observou-se a necessidade de revisão desse valor adotado pela legislação paulista de uso de resíduos orgânicos em solos.

ABSTRACT The agricultural use of sewage sludge and derivatives is to be carried out according to requirements established by Brazilian federal legislation and by legislation of the State of São Paulo, which requires that these organic materials must have at least 30 % of the total organic carbon degraded when incorporated in agricultural soils. To observe the degradation rates of sewage sludge and of organic compost produced from the same sewage sludge mixed with ground material from tree pruning, we performed two respirometry tests according to the modified method of Cetesb (1999). The waste materials were added to bottles containing 500 g of soil collected from the 0.00-0.20 m layer of a Nitossolo Háplico Álico (Hapludox) soil. In Test I, for sewage sludge (L) and sewage sludge compost (C), application rates were calculated to provide percentages of N requirements for one sugarcane cycle, in Mg ha-1(wet basis) of waste: L1 21.2 (100 %); L2 42.4 (200 %); C1 69.4 (50 %); C2 138.9 (100 %); and C3 277.8 (200 %). Test II was conducted only with sewage sludge, at the rates of 5, 10, 15, and 20 times higher than those recommended in Test I: L3 120; L4 240; L5 360; and L6 480. The CO2-C released was quantified by measuring electrical conductivity. In Test I, the treatments with sewage sludge had lower degradation rates than treatments with sewage sludge compost, probably due to the presence of recalcitrant substances formed during the humification phase of the composting process. The 30 % degradation rate was attained only by the application rate that was 20 times higher than the rate recommended for a cycle of sugarcane, and thus these waste products could not be used in clayey agricultural soils. Therefore, it is necessary to review the values established by legislation in the State of São Paulo.

Sewage sludge (SS) has been widely used as organic fertilizer. However, its continuous use can cause imbalances in soil fertility as well as soil-water-plant system contamination. The study aimed to evaluate possible improvements in the chemical and microbiological characteristics of domestic SS, with low heavy metal contents and pathogens, through the composting process. Two composting piles were set up, based on an initial C/N ratio of 30:1, with successive layers of tree pruning waste and SS. The aeration of piles was performed by mechanical turnover when the temperature rose above 65 ºC. The piles were irrigated when the water content was less than 50 %. Composting was conducted for 120 days. Temperature, moisture content, pH, electrical conductivity (EC), carbon and nitrogen contents, and fecal coliforms were monitored during the composting. A reduction of 58 % in the EC of the compost (SSC) compared with SS was observed and the pH reduced from 7.8 to 6.6. There was an increase in the value of cation exchange capacity/carbon content (CEC/C) and carbon content. Total nitrogen remained constant and N-NO3- + N-NH4+ were immobilised in organic forms. The C/N ratio decreased from 25:1 to 12:1. Temperatures above 55 ºC were observed for 20 days. After 60 days of composting, fecal coliforms were reduced from 107 Most Probable Number per gram of total solids (MPN g−1) to 104 MPN g−1. I one pile the 103 MPN g−1 reached after 90 days in one pile; in another, there was recontamination from 105 to 106 MPN g−1. In SSC, helminth eggs were eliminated, making application sustainable for agriculture purposes.

A determinação da taxa de mineralização de nitrogênio (N) em solos tratados com resíduos é fundamental para definir as doses a serem aplicadas, fornecendo N às plantas na época adequada, sem perdas do elemento por lixiviação. Inúmeros estudos em solos tratados com resíduos utilizam o teste de mineralização de N sem lixiviação e a caracterização das formas mineralizadas pelo método volumétrico. Em razão da deficiente repetibilidade do teste e da baixa sensibilidade do método de determinação observada em estudos com lodo de esgoto e composto orgânico, adotaram-se o método pouco difundido de mineralização de N com lixiviação e a especificação das formas minerais de N, por meio de métodos espectrofotométricos. O teste foi realizado em colunas de PVC, com 30 mm de diâmetro, preenchidas com terra retirada da camada 0,20 m de um solo classificado como Nitossolo Háplico, álico, argiloso, misturada às seguintes doses de resíduos, em Mg ha-1 (base úmida): lodo de esgoto - L1: 3,6; L2: 7,2; e L3: 14,4; e composto de lodo de esgoto e material vegetal triturado proveniente da poda de árvores urbanas - C1: 7,2; C2: 14,4; e C3: 28,8. As colunas foram incubadas e lixiviadas periodicamente com solução 0,01 mol L-1 KCl e as formas minerais de N determinadas colorimetricamente. Maiores taxas de mineralização ocorreram nas menores doses aplicadas de lodo e composto, evidenciando efeito priming, indesejado à fertilidade de solos sob condições tropicais. Menores taxas ocorreram nas doses L2 e C2, com valores próximos àqueles sugeridos pela legislação, não suprindo a demanda de N almejada, indicando possível necessidade de revisão na norma vigente. De modo geral, as taxas de mineralização foram maiores para o composto orgânico, enquanto a velocidade de degradação do composto orgânico foi menor que para o lodo, revelando maior distribuição da disponibilidade de N para a cultura ao longo do tempo. O método de mineralização com lixiviação e a determinação das formas de N-minerais por colorimetria evidenciaram-se rápidos e eficientes; estudos com solos e resíduos diversos podem validá-los para seu uso em rotina.

The determination of the nitrogen (N) mineralization rate in waste-treated soils is important to calculate the residue rates to be applied, supplying plants with mineral N to at the appropriate time, without leaching losses. Most studies on residue-treated soils use the technique without leaching of mineral forms and the volumetric determination method. The repeatability of the test is however poor and the sensitivity of the determination method low, especially in soils amended with sewage sludge and organic compost. In this study we adopted the not very well-known leaching method, with determination of N-mineral forms by spectrophotometer methods. In columns filled with soil taken from a depth of 0.20 m of an alic, loamy soil Hapludox, the following residues doses (Mg ha-1 - wet basis) were incorporated: Sewage sludge - L 1 = 3.6; L2 = 7.2; L3 = 14.4; and Organic compost (sewage sludge + tree cuttings) - C1 = 7.2, C2 = 14.4, C3 = 28.8. Columns were incubated and periodically leached with a 0.01 mol-1 L KCl solution, and the N-mineral forms were determined colorimetrically. High mineralization rates at lower sludge and compost rates were observed, indicating a priming effect, which is undesirable in soil management under tropical conditions. Lower N-mineralization rates were observed at L2 and C2, close to those suggested by the Brazilian legislation that regulates sewage sludge application to agricultural soils, but falling short of the N requirement, while higher mineralization rates were observed at the lower and higher doses, suggesting that the current legislation should be reviewed. Generally, the N mineralization rates were higher for organic compost than for sewage sludge, while the degradation speed was lower for the organic compost, indicating a greater distribution of the available N forms over time. The mineralization leaching method with determination of mineral-N forms by colorimetry proved to be fast and efficient, and more studies should test different soils and organic wastes for validation for routine use.

Zn availability in Red Latossol (Rhodic Ferralsol) of different pH amended with different rates of sewage sludge was studied by the isotopic 65Zn L value method. Soil chemical properties were found to be altered by SS addition. Zn concentration and Zn derived from SS (ZnpfSS) in plant, and Zn phytoavailability (L value), were increased with increasing SS rates. The linear correlation coefficient of plant Zn with SS rates and with L value was significant at 1% probability. The L value proved an efficient method for predicting Zn phytoavailability in sewage sludge-amended soil with different pH under the soil conditions studied.

O uso do lodo de esgoto na agricultura brasileira foi normatizado pela Resolução Conama nº 375, de 2006. No entanto, faltam pesquisas para adequar as doses complementares de adubos minerais nitrogenado e fosfatado a serem aplicadas em área agrícola tratada com lodo. Avaliaram-se os efeitos de doses de lodo de esgoto e de adubos minerais nitrogenado e fosfatado sobre a produtividade e as características tecnológicas da cana-planta e da primeira soqueira (efeito residual), em campo. Foram aplicadas quatro doses de lodo (0, 3,6, 7,2 e 10,8 t ha-1, base seca), de N (0, 30, 60 e 90 kg ha-1) e de P2O5 (0, 60, 120 e 180 kg ha-1), em delineamento em blocos casualizados, em esquema fatorial, com duas repetições. Para avaliar o efeito residual do lodo, foram aplicados 120 kg ha-1 de N e 140 kg ha-1 de K2O em todas as plotas. A aplicação de lodo no plantio da cana, combinado ou não com adubo mineral nitrogenado e, ou, fosfatado, aumentou a produtividade de colmos de 84 a 118 t ha-1, sem alterar a qualidade tecnológica da cana-de-açúcar, em relação à adubação NPK convencional, que produziu 91 t ha-1 de colmo. O estudo de superfície de resposta para a produtividade de colmo, em solo de baixa fertilidade, permitiu estabelecer sugestão de recomendação de adubo mineral nitrogenado e fosfatado para implantação de canavial, em função da dose de lodo, bem como concluir que a aplicação de 10,8 t ha-1 de lodo, ou seja, da dose estabelecida pelo critério do N, conforme Resolução Conama nº 375, pôde: reduzir o uso de N mineral em 100 % e o de P2O5 em 30 %, com aumento de produtividade de colmos em 22 %, em relação à adubação NPK convencional, como efeito direto do lodo sobre o cultivo da cana-planta; e aumentar a produtividade de colmos da primeira soqueira em até 12 % e a de açúcar em até 11 %, como efeito residual do lodo aplicado na cana-planta sobre o cultivo da cana-soca.

The use of sewage sludge in Brazilian agriculture was regulated by the resolution no. 375 Conama, in 2006. However, there is a lack of research to adequate the mineral N and P fertilizer doses to be applied in agricultural fields treated with this residue. In a field experiment, the effects of application rates of sewage sludge and mineral N and P fertilizers on the productivity and technical characteristics of the cane-plant and first ratoon (residual effect) crops were evaluated. Four doses of sewage sludge (0, 3.6, 7.2 and 10.8 t ha-1, dry base), of N (0, 30, 60 and 90 kg ha-1) and of P2O5 (0, 60, 120 and 180 kg ha-1) were combined in a factorial and laid out on randomized block design, a with two replications. To evaluate the residual effect of the sludge, 120 kg ha-1 N and 140 kg ha-1 of K2O were applied in all plots. Sludge application at cane planting, with or without N and/or P fertilizer increased the stalk yield from 84 up to 118 t ha-1, with no alteration in the sugarcane quality, compared with the application of NPK fertilizer alone, resulting in a stalk yield of 91 t ha-1. The study of the response surface for stalk yield on lowfertility soil was the basis for a recommendation of mineral N and P fertilizer doses for sugarcane implantation as related to sewage sludge application rates. It was also concluded that a sludge application of 10.8 t ha-1, which is the sludge dose established based on the N criterion according to the resolution Conama nº 375, could a) reduce the use of mineral N by 100 % and of P2O5 by 30 %, with increments of 22 % in stalk yield, as a direct effect of sludge application to cane plant crop, and b) increase the stalk yield in the second harvest (first ratoon) by up to 12 % and sugar yield by up to 11 %, by the residual effect of sludge application to sugar cane.

The objective of the study was to evaluate the effect of phosphorus on the Cd availability to plants of a contaminated soil using 109Cd isotope and chemical extractants. The experiment was set in a randomized block design and the soil was labeled with 222 KBq of 109Cd per pot and received 5 rates of P as triple superphosphate, growing lettuce plants as test crop. The use of phosphorus reduced pH of soil which altered the Cd availability in DTPA and Mehlich extractants. The lettuce Cd content decreased but its accumulation and L value increased in all treatments compared to the control, demonstrating the inefficiency of phosphorus in reducing the Cd availability.

The Cd phytoavailability in sewage sludge-amended soils of different pHs using the 109Cd L-value isotopic method and Cd extracted by DTPA has been determined. Maize plants (Zea mais L.) were grown under greenhouse conditions in a xanthic ferralsol at different pHs amended with five sewage sludge (SS) rates, and labeled with 74 kBq kg-1 of 109Cd. The SS rates altered the properties of the soil chemicals and these influenced the isotopic parameter (L-value) and percent of Cd uptake by plants from soil (%Cdpdfs) and SS (%CdpdfSS). L-values and Cd extracted by DTPA correlate significantly with SS rates and Cd uptake by plants and are efficient for predicting the Cd phytoavailability in the sewage sludge-amended soil.

The alteration of soil chemicals and its influence on availability (DTPA extractant method) and phytoavailability (63Ni L-value, isotopic method) of Ni was studied in sewage sludge-amended soil at different pHs. The soil pHs were 4.3, 5.3 and 5.9 and the rates of sewage sludge (SS) 0, 15, 30, 45 and 60 Mg ha-1. The chemical and physicochemical soil characteristics were altered by the SS rate and increased the Ni availability and phytoavailability. The isotopic method (63Ni L-value) was more efficient in predicting the Ni phytoavailability that the Ni-DTPA extractant in soil pHs 5.3 and 5.9.

Em experimento realizado no campo, nos anos agrícolas 1996/97 e 1997/98, em Latossolo Amarelo distrófico, cultivado com cana-de-açúcar, avaliou-se o efeito de aplicações sucessivas de composto de lixo urbano sobre a movimentação, em profundidade, dos metais Cd, Cr, Cu, Ni, Pb e zinco. No primeiro ano agrícola, além do tratamento testemunha, o composto de lixo foi aplicado nas doses de 20, 40 e 60 Mg ha-1 (base seca). No segundo ano, o composto foi reaplicado nas doses de 24, 48 e 72 Mg ha-1. Em relação aos metais Cd, Cr, Cu, Ni e Pb não se observou nenhuma evidência de movimentação ao longo do perfil do solo. O Zn apresentou mobilidade no solo, onde se verificou, ao final de 1997/98, incrementos significativos até a camada de 0,4-0,6 m de profundidade.

From 1996 to 1998, a field experiment was carried out to study the effects of successive application of a municipal solid waste compost on the movement of Cd, Cr, Cu, Ni, Pb, and Zn through the profile of a Yellow Latossol (Typic Hapludox) cropped with sugarcane. The compost was applied at rates of 20, 40 and 60 Mg ha-1 (dry base) in the first year, and of 24, 48 and 72 Mg ha-1 in the second year, respectively, plus a control treatment. The results demonstrated that there was no movement of Cd, Cr, Cu, Ni, and Pb through the profile of this acid soil. Nevertheless, Zn mobility was verified at the end of the second year, when content of Zn increased from 0.4 to 0.6 m layer.

Experimento de campo foi conduzido, nos anos agrícolas 1996/97 e 1997/98, para avaliar os efeitos de aplicações sucessivas de composto de lixo urbano sobre os teores de carbono orgânico, condutividade elétrica, pH e capacidade de troca de cátions (CTC) ao pH atual de um Latossolo Amarelo distrófico em que foi cultivada cana-de-açúcar. No primeiro ano agrícola, além dos tratamentos calagem + adubação mineral e testemunha, o composto de lixo foi aplicado nas doses de 20, 40 e 60 Mg ha-1 (base seca). No segundo ano, o composto foi reaplicado nas doses de 24, 48 e 72 Mg ha-1. Todas as propriedades químicas do solo estudadas aumentaram com as doses do composto, em ambos os anos agrícolas. Os incrementos observados nesses atributos, da primeira para a segunda aplicação, foram significativos, exceto a condutividade elétrica, que, embora tenha aumentado logo após a aplicação do resíduo, não atingiu níveis críticos e teve seus valores reduzidos com o tempo. Acúmulos nos teores de C orgânico do solo foram diretamente proporcionais às doses de aplicação. O aumento da CTC do solo foi conseqüência direta dos incrementos nos teores de C orgânico e nos valores de pH.

A field experiment was conducted, during the years of 1996/97 and 1997/98, to evaluate the effects of the successive application of solid urban waste compost on organic carbon, electrical conductivity, pH, and cation exchange capacity (CEC) at field pH in a Typic Hapludox cropped with sugarcane. In the first year, besides lime + mineral fertilizer and control treatments, the compost was applied at a rate of 0, 20, 40, and 60 Mg ha-1 (dry basis). In the second year, the compost was reapplied at a rate of 24, 48, and 72 Mg ha-1. All studied soil properties increased with rate of compost application in both years. Attributes increments from the first to the second application were significant, except for electrical conductivity, which increased soon after the residue application, but did not reach critical levels and decreased along the time. Accumulation of organic C in soil was direct proportional to compost application rate. The increase of soil CEC was a consequence of the increments on organic C content and pH value.