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Residual effect of sewage sludge fertilization on sunflower yield and nutrition

Efeito residual da adubação com lodo de esgoto sobre a produção e nutrição de girassol

ABSTRACT

This study aimed to evaluate the residual effect of sewage sludge fertilization on yield and nutrition of sunflower in its second cycle. The experiment was carried out from April to August 2012. The treatments consisted of four doses of sewage sludge (0, 10, 20 and 30 t ha-1, dry basis) applied in the first cycle of sunflower, distributed in a randomized block design, with six replicates. Sunflower stem diameter, plant height, capitulum diameter and yield increased with the increment in sewage sludge doses, with maximum values observed with the dose of 30 t ha-1. The contents of calcium and magnesium in the soil, pH, sum of bases, effective and potential cation exchange capacity and base saturation increased, while potential acidity and the contents of manganese and iron in the leaves decreased, with the increment in the residual doses of sewage sludge. There was a reduction in yield and growth characteristics of sunflower in the second cycle; thus, additional fertilization with sewage sludge is recommended in each new cycle.

Key words:
oilseeds; biosolid; organic fertilization

RESUMO

Neste trabalho objetivou-se avaliar o efeito residual da adubação com lodo de esgoto sobre a produção e nutrição do girassol em segundo cultivo. O experimento foi realizado no período de abril a agosto de 2012. Os tratamentos corresponderam a quatro doses de lodo de esgoto (0; 10; 20 e 30 t ha-1, em base seca) aplicadas no primeiro cultivo de girassol, distribuídas no delineamento em blocos casualizados, com seis repetições. O diâmetro do caule, a altura da planta, o diâmetro do capítulo e a produtividade do girassol aumentaram com o incremento de lodo de esgoto sendo os valores máximos observados na dose de 30 t ha-1. Os teores de cálcio e magnésio no solo, o pH, a soma de bases, a capacidade de troca catiônica efetiva e potencial e a percentagem de saturação de bases aumentaram enquanto a acidez potencial e os teores manganês e ferro na folha diminuíram com o incremento das doses residuais de lodo de esgoto. Houve redução na produtividade e nas características de crescimento do girassol no segundo cultivo, recomendando-se novas adubações com lodo, a cada plantio.

Palavras-chave:
oleaginosas; biossólido; adubação orgânica

Introduction

The agricultural use of sewage sludge is a viable alternative, since it contains high contents of organic matter and nutrients, and can complement mineral fertilization and reduce production costs (Biondi & Nascimento, 2005Biondi, C. M.; Nascimento, C. W. A. Acúmulo de nitrogênio e produção de matéria seca de plantas em solos tratados com lodo de esgoto. Revista Caatinga, v.18, p.123-128, 2005.; Lemainski & Silva, 2006Lemainski, J.; Silva, J. E. Utilização do biossólido da CAESB na produção de milho no Distrito Federal. Revista Brasileira de Ciência de Solo, v.30, p.741 750, 2006. http://dx.doi.org/10.1590/ S0100-06832006000400015
http://dx.doi.org/10.1590/ S0100-0683200...
). In addition, it allows the return of organic residues produced in urban areas to the field, increasing agricultural sustainability (Barbosa et al., 2007Barbosa, G. M. C.; Tavares Filho, J.; Brito, O. R.; Fonseca, I. C. B. Efeito residual do lodo de esgoto na produtividade do milho safrinha. Revista Brasileira de Ciência de Solo, v.31, p.601-605, 2007. http://dx.doi.org/10.1590/S0100-06832007000300020
http://dx.doi.org/10.1590/S0100-06832007...
). However, it has potential risks of soil and plant contamination with heavy metals, pathogenic microorganisms and organic contaminants (Nascimento et al., 2014Nascimento, A. L.; Sampaio, R. A.; Zuba Junio, G. R.; Carneiro, J. P.; Fernandes, L. A.; Rorrigues, M. N. Teores de metais pesados no solo e em girassol adubado com lodo de esgoto. Revista Brasileira Engenharia Agrícola Ambiental, v.18, p.294-300, 2014. http://dx.doi.org/10.1590/S1415-43662014000300008
http://dx.doi.org/10.1590/S1415-43662014...
; 2015Nascimento, A. L.; Zuba Junio, G. R.; Sampaio, R. A.; Fernandes, L. A.; Carneiro, J. P.; Barbosa, C. F. Metais pesados no solo e mamoneira adubada com biossólido e silicato de cálcio e magnésio. Revista Brasileira Engenharia Agrícola Ambiental, v.19, p.505-511, 2015. http://dx.doi.org/10.1590/1807-1929/agriambi.v19n5p505-511
http://dx.doi.org/10.1590/1807-1929/agri...
).

The positive effect of sewage sludge in agriculture was confirmed by Nascimento et al. (2011)Nascimento, A. L.; Sampaio, R. A.; Brandão Júnior, D. S.; Zuba Junio, G. R.; Fernandes, L. A. Crescimento e produtividade de semente de mamona tratada com lodo de esgoto. Revista Caatinga, v.24, p.145-151, 2011., who observed a good response of papaya plants to the increase in sewage sludge doses. These authors also found agronomic efficiency index of 198% for the application of 60 t ha-1 of sewage sludge, compared with chemical fertilization, which evidences the potential of sewage sludge in the improvement of soil physical and chemical characteristics.

Besides the immediate effect of its application, sewage sludge can show residual effect in successive crop cycles and reduce production costs for farmers. Lemainski & Silva (2006)Lemainski, J.; Silva, J. E. Utilização do biossólido da CAESB na produção de milho no Distrito Federal. Revista Brasileira de Ciência de Solo, v.30, p.741 750, 2006. http://dx.doi.org/10.1590/ S0100-06832006000400015
http://dx.doi.org/10.1590/ S0100-0683200...
observed that fertilization with 30 t ha-1 of sewage sludge caused significant residual effect on maize and a yield corresponding to 77% of that from the first cycle, being 22% more efficient than mineral fertilizer, which points out the importance of using sewage sludge as a residual source of nutrients. Godoi et al. (2008)Godoi, E. L.; Borges, J. D.; Ximenes, P.A.; Leandro, W. M. Produtividade de Stylosantes guianensis cv. mineirão em resposta ao efeito residual de biossólido em área degradada. Pesquisa Agropecuária Tropical, v.38, p.158-163, 2008. observed beneficial residual effect of sewage sludge on the chemical, physical and biological components of a degraded soil, which promoted yield increment in the second cut of Stylosanthes guianensis cv. 'Mineirão', at 273 days after the first harvest and at 423 days of cultivation.

Based on the above, this study aimed to evaluate the residual effect of sewage sludge fertilization on soil and on sunflower growth, yield and leaf nutrient contents.

Material and Methods

The experiment was carried out from April to August 2012, at the ICA/UFMG, in Montes Claros-MG, Brazil (16º51'38" S; 44º55'00" W). According to Köppen's classification, the climate of the region is Aw. The soil in the area is a Nitosol, with the following attributes in the layers of 0-20 and 20-40 cm (Table 1):

Table 1
Chemical and physical characteristics of the soil before the first crop cycle

The single-cross hybrid 'Hélio 250' of sunflower (Helianthus annuus L.) was planted one year after the harvest of the first cycle, in order to evaluate the residual effect of sewage sludge fertilization, at the doses of 0, 10, 20 and 30 t ha-1, on a dry basis. Seeding was performed in the same rows of the first cycle, after incorporating crop residues. The treatments were arranged in a randomized block design, with six replicates.

The sewage sludge used as organic fertilizer was collected in the sewage treatment plant of Montes Claros-MG, administered by the Sanitation Company of Minas Gerais (COPASA-MG). The treatment line consists of a pre-treatment and an upflow anaerobic sludge blanket (UASB) reactor, where the sludge is centrifuged and dewatered using a thermal drier at 350 ºC for 30 min.

The sewage sludge doses applied in the first crop cycle were calculated based on the content of available N in the fertilizer (6.0 kg t-1), determined according to the Resolution nº 375 of the National Environmental Council - CONAMA (Brasil, 2006Brasil. Ministério do Meio Ambiente. Resolução nº 375 de 29 de agosto de 2.006. http://www.mma.gov.br/conama/. 1 Nov. 2009.
http://www.mma.gov.br/conama/...
), and on the sunflower N demand for the state of Minas Gerais (60 kg ha-1) (CFSEMG, 1999CFSEMG - Comissão de Fertilidade do Solo do Estado de Minas Gerais. Recomendação para uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. 359p.). The chemical characteristics of the sewage sludge are described in Table 2.

Table 2
Chemical characteristics of the sewage sludge and contents of nutrients applied according to the different doses

The experimental plots consisted of four 3-m long rows, with spacing of 0.3 m between plants and 0.8 m between rows. The two central rows (20 plants) of each experimental unit were used for the analyses, disregarding 0.5 m on each side, considered as borders.

Furrows were manually opened using a hoe until the depth of 20 cm. Three seeds were planted in each hole and thinning was performed 15 days after emergence, leaving only one plant. At 30 and 60 days after planting, manual weedings were performed for the control of unwanted plants. Sprinkler irrigation, three times a week, was performed during the crop cycle.

At the beginning of the flowering stage, leaf samples were collected from the upper third section of the leaves (Malavolta et al., 1997Malavolta, E.; Vitti, G. C.; Oliveira, S. A. Avaliação do estado nutricional das plantas: princípios e aplicações. 2.ed. Piracicaba: POTAFOS, 1997. 319p.) of 12 plants in the experimental plot, for the analyses of N, P, K, Ca, Mg, S, Zn, Cu, Mn, Fe and B (Tedesco et al., 1995Tedesco, M. J.; Volkweiss, S. J.; Bohmen, H. Análise de solo, plantas e outros materiais. 2.ed. Porto Alegre: Departamento de Solos/ UFRGS, 1995. 174p. Boletim Técnico, 5).

At the end of the experiment, in the harvesting stage (R9), when the capitula were facing down, the following variables were evaluated: stem diameter, using a digital caliper near the soil surface; plant height, using a steel tape measure from the soil surface to the apex of the plant; and capitulum diameter, determined with a tape measure. In addition, grain yield was estimated using the weight of grains corrected to 12% of humidity, considering all the grains collected in each plant.

After harvesting, 8 subsamples of soil were collected in each experimental plot from the layers of 0-20 and 20-40 cm, in order to form composite samples for the analyses of organic matter, pH, P, K, Ca, Mg, S, H+Al, Al, Zn, Cu, Mn and Fe (EMBRAPA, 1997), and B (Tedesco et al., 1995Tedesco, M. J.; Volkweiss, S. J.; Bohmen, H. Análise de solo, plantas e outros materiais. 2.ed. Porto Alegre: Departamento de Solos/ UFRGS, 1995. 174p. Boletim Técnico, 5). Then, sum of bases (SB), effective cation exchange capacity (CEC(t)), potential cation exchange capacity (CEC(T)) and the percentage of base saturation (V%) (EMBRAPA, 1997) were calculated.

The data were subjected to the analysis of variance and the sewage sludge doses were fitted to regression models, testing the coefficients until 0.1 probability level by t-test. For the comparison between variables from the first and second cycle, the confidence intervals of the means were calculated, considering a 0.05 probability level by t-test.

Results and Discussion

Residual effect of sewage sludge fertilization was observed on sunflower yield (Table 3), which reached a maximum value of 1,073.47 kg ha-1 for the dose of 30 t ha-1 of sewage sludge, which corresponds to 72% of the mean yield in Brazil estimated for the 2011/2012 crop season, under irrigated and rainfed conditions, according to CONAB (2012)CONAB - Companhia Nacional De Abastecimento. Banco de dados agregados. 2012. < http//www.conab.gov.br >. 28 Jan 2012.
http//www.conab.gov.br...
. These results corroborate those observed by Barbosa et al. (2007)Barbosa, G. M. C.; Tavares Filho, J.; Brito, O. R.; Fonseca, I. C. B. Efeito residual do lodo de esgoto na produtividade do milho safrinha. Revista Brasileira de Ciência de Solo, v.31, p.601-605, 2007. http://dx.doi.org/10.1590/S0100-06832007000300020
http://dx.doi.org/10.1590/S0100-06832007...
and Zuba Junio et al. (2012)Zuba Junio, G. R.; Sampaio, R. A.; Santos, G. B.; Nascimento, A. L.; Carneiro, J. P.; Santos, L. D. T.; Fernandes, L. A. Produção de milho adubado residualmente com composto de lodo de esgoto e fosfato de Gafsa. Revista Brasileira de Engenharia Agrícola e Ambiental, v.16, p.1289-1297, 2012. http://dx.doi.org/10.1590/S1415-43662012001200005
http://dx.doi.org/10.1590/S1415-43662012...
, who observed a positive response in maize yield to the residual effect of sewage sludge application in the soil. According to Nascimento et al. (2014)Nascimento, A. L.; Sampaio, R. A.; Zuba Junio, G. R.; Carneiro, J. P.; Fernandes, L. A.; Rorrigues, M. N. Teores de metais pesados no solo e em girassol adubado com lodo de esgoto. Revista Brasileira Engenharia Agrícola Ambiental, v.18, p.294-300, 2014. http://dx.doi.org/10.1590/S1415-43662014000300008
http://dx.doi.org/10.1590/S1415-43662014...
, the increase in the yield of crops fertilized with sewage sludge is due to the improvement in soil chemical, physical and biological quality.

Table 3
Regression equations between yield (Y), stem diameter (SD), plant height (PH) and head diameter (HD) of sunflower and the doses of sewage sludge

Stem diameter, plant height and capitulum diameter increased with the increments in the residual doses of sewage sludge, for the application of up to 30 t ha-1 (Table 3). In addition, the positive and statistically significant correlation between capitulum growth and grain yield (r = 0.94**) must be pointed out. Plant height results corroborate those obtained by Costa et al. (2009)Costa, F. X.; Lima, V. L. A.; Beltrão, N. E. M.; Azevedo, C. A. V.; Soares, F. A. L.; Alva, L. D. M. Efeitos residuais da aplicação de biossólidos e da irrigação com água residuária no crescimento do milho. Revista Brasileira de Engenharia Agrícola e Ambiental, v.13, p.687-693, 2009. http://dx.doi.org/10.1590/S1415-43662009000600004
http://dx.doi.org/10.1590/S1415-43662009...
, who observed residual effect of sewage sludge on the height of maize plants for the application of 75 and 150 kg ha-1. On the other hand, these authors did not observe significant increments in stem diameter, despite using sewage sludge doses higher than those tested in this study.

P availability values in the evaluated soil layers were classified as very good and medium (Alvarez V. et al., 1999Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.), and were not influenced by the residual effect of the sewage sludge fertilization (Table 4). Although the sewage sludge has supplied P (Table 1), the amounts were only enough for the first crop cycle. These results differ from those observed by Barbosa et al. (2007)Barbosa, G. M. C.; Tavares Filho, J.; Brito, O. R.; Fonseca, I. C. B. Efeito residual do lodo de esgoto na produtividade do milho safrinha. Revista Brasileira de Ciência de Solo, v.31, p.601-605, 2007. http://dx.doi.org/10.1590/S0100-06832007000300020
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, who reported increments in soil P contents caused by the residual effect of sewage sludge application.

Table 4
Regression equations between soil nutrient contents and the residual doses of sewage sludge

There was no residual effect of sewage sludge fertilization on K contents in the soil (Table 4), which were classified as good according to Alvarez V. et al. (1999)Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.. Similar results were reported by Barbosa et al. (2007)Barbosa, G. M. C.; Tavares Filho, J.; Brito, O. R.; Fonseca, I. C. B. Efeito residual do lodo de esgoto na produtividade do milho safrinha. Revista Brasileira de Ciência de Solo, v.31, p.601-605, 2007. http://dx.doi.org/10.1590/S0100-06832007000300020
http://dx.doi.org/10.1590/S0100-06832007...
, who did not observe residual effect of sewage sludge application on K contents in the soil.

Ca contents in the layer of 0-20 cm were not influenced by the residual effect of sewage sludge fertilization. However, this effect was significant for the layer of 20-40 cm, and the highest value was obtained for the maximum dose of sewage sludge, 30 t ha-1 (Table 4). This can be related to the movement of Ca supplied by the highest sewage sludge doses to the layer of 20-40 cm. Nevertheless, Ca contents in the studied layers were classified as very good (Alvarez V. et al., 1999Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.). Zuba Junio et al. (2012)Zuba Junio, G. R.; Sampaio, R. A.; Santos, G. B.; Nascimento, A. L.; Carneiro, J. P.; Santos, L. D. T.; Fernandes, L. A. Produção de milho adubado residualmente com composto de lodo de esgoto e fosfato de Gafsa. Revista Brasileira de Engenharia Agrícola e Ambiental, v.16, p.1289-1297, 2012. http://dx.doi.org/10.1590/S1415-43662012001200005
http://dx.doi.org/10.1590/S1415-43662012...
, studying maize, observed residual effect of the application of increasing doses of a sewage sludge compound in all the studied soil layers, until the dose of approximately 39 t ha-1.

As observed for Ca, Mg contents in the soil were influenced by the residual effect of sewage sludge doses in the layer of 20-40 cm, with the highest value observed for the dose of 30 t ha-1 (Table 4), which did not occur for the layer of 0-20 cm. As observed for Ca, part of the Mg applied with the highest sewage sludge doses moved to the layer of 20-40 cm. Increase in the Mg contents in the soil as a function of the residual effect of sewage sludge fertilization was also observed by Barbosa et al. (2007)Barbosa, G. M. C.; Tavares Filho, J.; Brito, O. R.; Fonseca, I. C. B. Efeito residual do lodo de esgoto na produtividade do milho safrinha. Revista Brasileira de Ciência de Solo, v.31, p.601-605, 2007. http://dx.doi.org/10.1590/S0100-06832007000300020
http://dx.doi.org/10.1590/S0100-06832007...
. The available contents of this nutrient were classified as good in the present study (Alvarez V. et al., 1999Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.).

There was no residual effect of the sewage sludge doses on S contents (Table 4), which were classified as very good in both evaluated layers, according to Alvarez V. et al. (1999)Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32..

The contents of micronutrients were not influenced by the residual effects of the sewage sludge doses applied in the first crop cycle (Table 4). These results differ from those reported by Oliveira et al. (2005)Oliveira, K. W.; Melo, W. J.; Pereira, G. T.; Melo, V. P.; Melo, G. M. P. Heavy metals in oxisols amended with biosolids and cropped with maize in a long-term experiment. Scientia Agricola, v.62, p.381-388, 2005. http://dx.doi.org/10.1590/S0103-90162005000400012
http://dx.doi.org/10.1590/S0103-90162005...
, who observed residual effect for Zn, which tended to remain in the layer of 0-20 cm. Sukkariyah et al. (2005)Sukkariyah, B. F.; Evanylo, G.; Zelazny, L.; Chane Y. R. L. Recovery and distribution of biosolids-derived trace metals in a clay loam soil. Journal of Environmental Quality, v.34, p.1843-1850, 2005. http://dx.doi.org/10.2134/jeq2004.0180
http://dx.doi.org/10.2134/jeq2004.0180...
observed that, after 17 years of cultivation, more than 75% of Zn and 85% of Cu applied through sewage sludge fertilization remained in the layer of incorporation, which is not desirable, because of the possibility of reaching phytotoxic levels. Among the micronutrients evaluated in this study, only B showed contents classified as low and very low (Alvarez V. et al., 1999Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.) in the layers of 0-20 and 20-40 cm, respectively (Table 4). This fact can be explained by the low B content supplied to the soil through the sewage sludge fertilization in the first crop cycle (Table 2), which corresponded to 1/3 of the amount recommended for sunflower cultivation.

There was no residual effect of sewage sludge application, in any of the evaluated layers, on the organic matter contents, which were classified as medium, according to Alvarez V. et al. (1999)Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32. (Table 5). Antolin et al. (2005Antolin, M. C.; Pascual, I; Garcia, C.; Polo, A.; Díaz, M. S. Growth, yield and solute content of barley in soils treated with sewage sludge under semiarid Mediterranean conditions. Field Crops Research, v.94, p.224-237, 2005. http://dx.doi.org/10.1016/j.fcr.2005.01.009
http://dx.doi.org/10.1016/j.fcr.2005.01....
) observed that, one year after sewage sludge application, the organic matter contents were similar in fertilized and non-fertilized plots, because of a rapid mineralization of the organic matter, which is corroborated by the results of the present study. However, Barbosa et al. (2007)Barbosa, G. M. C.; Tavares Filho, J.; Brito, O. R.; Fonseca, I. C. B. Efeito residual do lodo de esgoto na produtividade do milho safrinha. Revista Brasileira de Ciência de Solo, v.31, p.601-605, 2007. http://dx.doi.org/10.1590/S0100-06832007000300020
http://dx.doi.org/10.1590/S0100-06832007...
reported residual increase of soil organic matter with the application of sewage sludge.

Table 5
Regression equations relating chemical attributes and fertility indices with the residual effect of sewage sludge doses applied to the soil

For soil pH (Table 5), there was residual effect of sewage sludge fertilization in the layer of 20-40 cm, with values classified as very high (Alvarez V. et al., 1999Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.), corresponding to 7.3 at the dose of 30 t ha-1. These results confirm those obtained by Barbosa et al. (2007)Barbosa, G. M. C.; Tavares Filho, J.; Brito, O. R.; Fonseca, I. C. B. Efeito residual do lodo de esgoto na produtividade do milho safrinha. Revista Brasileira de Ciência de Solo, v.31, p.601-605, 2007. http://dx.doi.org/10.1590/S0100-06832007000300020
http://dx.doi.org/10.1590/S0100-06832007...
, who found that the residual effect of the application of increasing doses of sewage sludge promoted increase in soil pH. On the other hand, Antolin et al. (2005)Antolin, M. C.; Pascual, I; Garcia, C.; Polo, A.; Díaz, M. S. Growth, yield and solute content of barley in soils treated with sewage sludge under semiarid Mediterranean conditions. Field Crops Research, v.94, p.224-237, 2005. http://dx.doi.org/10.1016/j.fcr.2005.01.009
http://dx.doi.org/10.1016/j.fcr.2005.01....
and Caldeira Júnior et al. (2009)Caldeira Júnior, C. F.; Souza, R. A.; Santos, A. M.; Sampaio, R. A.; Martins, E. R. Características químicas do solo e crescimento de Astronium fraxinifolium Schott em área degradada adubada com lodo de esgoto e silicato de cálcio. Revista Ceres, v.56, p.213-218, 2009. observed that doses of up to 30 t ha-1 caused a reduction in this variable, which can be associated with the production of organic acids during the degradation of the residues by the microorganisms. The increase in soil pH, due to the application of sewage sludge, observed in some studies, can be due to the alkalinity of the materials used in processes of pathogen elimination and sludge stabilization (Nascimento et al., 2004Nascimento, C. W. A.; Barros, D. A. S.; Melo, E. E. C.; Oliveira, A. B. Alterações químicas em solos e crescimento de milho e feijoeiro após aplicação de lodo de esgoto. Revista Brasileira de Ciência do Solo, v.28, p.385-392, 2004. http://dx.doi.org/10.1590/S0100-06832004000200017
http://dx.doi.org/10.1590/S0100-06832004...
). In this study, it should be taken into consideration that pH values classified as very high in both evaluated layers can be related to the use of calcareous water in the irrigation, which shows the following characteristics: pH = 7.6; electrical conductivity = 468 us cm-1 and total hardness and CaCO3 = 222 mg L-1.

The residual effect of sewage sludge application was observed for SB, CEC(t)and CEC(T) only in the layer of 20-40 cm, which showed levels classified from good to very good (Alvarez V. et al., 1999Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.) in both evaluated layers (Table 5). According to Barbosa et al. (2007)Barbosa, G. M. C.; Tavares Filho, J.; Brito, O. R.; Fonseca, I. C. B. Efeito residual do lodo de esgoto na produtividade do milho safrinha. Revista Brasileira de Ciência de Solo, v.31, p.601-605, 2007. http://dx.doi.org/10.1590/S0100-06832007000300020
http://dx.doi.org/10.1590/S0100-06832007...
, sewage sludge increases in soil negative charges, due to its high content of organic matter, besides enriching the medium with Ca and Mg, which contributes to the increase of soil CEC.

The treatments with sewage sludge showed residual effect on V% values in the layers of 0-20 and 20-40 cm (Table 5), which are classified as very good with respect to fertility (Alvarez V. et al., 1999Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.). These results in the layer of 0-20 cm corroborate those obtained by Barbosa et al. (2007)Barbosa, G. M. C.; Tavares Filho, J.; Brito, O. R.; Fonseca, I. C. B. Efeito residual do lodo de esgoto na produtividade do milho safrinha. Revista Brasileira de Ciência de Solo, v.31, p.601-605, 2007. http://dx.doi.org/10.1590/S0100-06832007000300020
http://dx.doi.org/10.1590/S0100-06832007...
, who observed an increase in base saturation in the layer of 0-20 cm caused by the residual effect of sewage sludge application, due to the supply of Ca and Mg by the organic matter.

H+Al values were influenced by the residual effect of sewage sludge in the layers of 0-20 and 20-40 cm (Table 5), but were classified as very low, according to Alvarez V. et al. (1999)Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.. For Al, no residual effect was observed in any of the evaluated layers.

The contents of macronutrients in sunflower leaves were not influenced by the residual effect of sewage sludge applied in the first cycle; Mg and S remained below the nutrient sufficiency range in the plant (Table 6) (Albuquerque et al., 2015Albuquerque, H. C. de; Zuba Junio, G. R.; Sampaio, R. A.; Fernandes, L. A.; Zonta, E.; Barbosa, C. F. Yield and nutrition of sunflower fertilized with sewage sludge. Revista Brasileira de Engenharia Agrícola e Ambiental, v.19, p.553-559, 2015. http://dx.doi.org/10.1590/1807-1929/agriambi.v19n6p553-559
http://dx.doi.org/10.1590/1807-1929/agri...
). According to Zuba Junio et al. (2012)Zuba Junio, G. R.; Sampaio, R. A.; Santos, G. B.; Nascimento, A. L.; Carneiro, J. P.; Santos, L. D. T.; Fernandes, L. A. Produção de milho adubado residualmente com composto de lodo de esgoto e fosfato de Gafsa. Revista Brasileira de Engenharia Agrícola e Ambiental, v.16, p.1289-1297, 2012. http://dx.doi.org/10.1590/S1415-43662012001200005
http://dx.doi.org/10.1590/S1415-43662012...
, the residual effects of sewage sludge fertilization influence the leaf contents of N, P and K, after one year of its application in the soil and two consecutive maize cycles. Still according to these authors, the contents of Mg and S remain below the amounts demanded by maize, which confirms the results obtained in this experiment and indicates the need for additional sewage sludge fertilization in each new cycle of sunflower.

Table 6
Regression equations between the nutrient contents in sunflower leaves and the residual doses of sewage sludge

The contents of micronutrients in sunflower leaves (Table 6) were not influenced by the residual effect of sewage sludge application, except for Mn and Fe. The contents of these elements decreased as the doses increased, which was possibly associated with the increase in pH in the layer of 20-40 cm (Table 5). In addition, micronutrient contents remained within the nutrient sufficiency range for sunflower. These results differ from those reported by Zuba Junio et al. (2011)Zuba Junio, G. R.; Sampaio, R. A.; Santos, G. B.; Nascimento, A. L.; Prates, F. B. S.; Fernandes, L. A. Metais pesados em milho fertilizado com fosfato natural e composto de lodo de esgoto. Revista Brasileira de Engenharia Agrícola e Ambiental, v.15, p.1082-1088, 2011. http://dx.doi.org/10.1590/S1415-43662011001000013
http://dx.doi.org/10.1590/S1415-43662011...
, who observed increase in Zn contents of maize plants with the increment in the residual fertilization with sewage sludge of up to 63.62 t ha-1, an effect also observed for other doses by Gomes et al. (2007)Gomes, S. B. V.; Nascimento, C. W. A.; Biondi, C. M. Produtividade e composição mineral de plantas de milho em solo adubado com lodo de esgoto. Revista Brasileira de Engenharia Agrícola e Ambiental, v.11, p.459-465, 2007. http://dx.doi.org/10.1590/S1415-43662007000500002
http://dx.doi.org/10.1590/S1415-43662007...
. In addition, Zuba Junio et al. (2011)Zuba Junio, G. R.; Sampaio, R. A.; Santos, G. B.; Nascimento, A. L.; Prates, F. B. S.; Fernandes, L. A. Metais pesados em milho fertilizado com fosfato natural e composto de lodo de esgoto. Revista Brasileira de Engenharia Agrícola e Ambiental, v.15, p.1082-1088, 2011. http://dx.doi.org/10.1590/S1415-43662011001000013
http://dx.doi.org/10.1590/S1415-43662011...
did not observe effect of sewage sludge treatments on the contents of Cu in the plant, which corroborates the results obtained in this study.

Sunflower yield in the second cycle corresponded to 71% of the yield in the first cycle and the biometric characteristics also decreased (Table 7). These results for grain yield are similar to those reported by Lemainski & Silva (2006)Lemainski, J.; Silva, J. E. Utilização do biossólido da CAESB na produção de milho no Distrito Federal. Revista Brasileira de Ciência de Solo, v.30, p.741 750, 2006. http://dx.doi.org/10.1590/ S0100-06832006000400015
http://dx.doi.org/10.1590/ S0100-0683200...
, who observed that the application of sewage sludge doses of 30 and 45 t ha-1 promoted yields corresponding to 77 and 80% of those from the first cycle, respectively. In the present study, the reduction in yield and biometric characteristics can be related to the contents of organic matter and S in the soil, which decreased from the first to the second cycle, besides the low contents of B in both cycles. Despite the reduction, the contents of soil organic matter were classified as medium (Alvarez V. et al., 1999Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.). Although there was no statistical difference between the means of P and K from the first to the second cycle, the reduction contributed to a change in the agronomic classification (Alvarez V. et al., 1999Alvarez V., V. H.; Novais, R. F.; Barros, N. F.; Cantarutti, R. B.; Lopes, A. S. Interpretação dos resultados das análises de solos. In: Ribeiro A. C.; Guimarães P. T. G.; Alvarez V., V. H. (org.) Recomendações para o uso de corretivos e fertilizantes em Minas Gerais: 5ª aproximação. Viçosa: CFSEMG, 1999. Cap.5, p.25-32.) in the layer of 20-40 cm for P, from good to medium, and in the layer of 0-20 cm for K, from very good to good. Thus, additional fertilization with sewage sludge is recommended in each cycle.

Table 7
Confidence interval of the means for yield, biometric characteristics, chemical attributes, fertility indices and soil nutrient contents in two consecutive cycles of sunflower

As shown in Table 8, the contents of macronutrients in the leaves remained within the sufficiency range for this crop (Malavolta et al., 1997Malavolta, E.; Vitti, G. C.; Oliveira, S. A. Avaliação do estado nutricional das plantas: princípios e aplicações. 2.ed. Piracicaba: POTAFOS, 1997. 319p.), except for Mg and S, which could be a limitation for plant growth and development. It should be pointed out that the contents of K were higher in the second cycle in comparison to the first one.

With respect to the micronutrients in plant leaves, there was an increase in the contents of Cu and Zn in the second cycle (Table 8). Cu content was within the adequate nutritional range for this crop (Oliveira, 2009Oliveira, J. P. B.; Lopes, J. C.; Alexandre, R. S.; Jasper, A. P. S.; Santos, L. N. S.; Oliveira, L. B. Concentração de metais pesados em plantas de maracujá doce cultivadas em dois solos tratados com lodo de esgoto. Engenharia Ambiental, v.6, p.217-223, 2009.), which was not observed in the first cycle. Fe leaf contents were lower in the second cycle (Table 8), which can be attributed to the insolubilization of this element at pH close to alkalinity and to the complexing power of the organic matter, which reduces the availability of P for plants (Cunha et al., 2011Cunha, E.; Stone, L. F.; Didonel, A. G.; Ferreira, E. P. B.; Moreira, J. A. A.; Leandro, W. M. Atributos químicos de solo sob produção orgânica influenciados pelo preparo e por plantas de cobertura. Revista Brasileira de Engenharia Agrícola e Ambiental, v.15, p.1021-1029, 2011. http://dx.doi.org/10.1590/S1415-43662011001000005
http://dx.doi.org/10.1590/S1415-43662011...
). B leaf contents were also reduced compared with the first cycle, which can be related to its low concentration in the sewage sludge applied to the soil.

Table 8
Confidence intervals of the means for nutrient contents in sunflower leaves, in two consecutive cycles

Conclusions

1. Sewage sludge doses of up to 30 t ha-1 increased growth and yield of sunflower plants in the second cycle; however, the response is lower compared with the first cycle and additional fertilization with sewage sludge is recommended in each new cycle.

2. The contents of organic matter and nutrients in the soil, except calcium and magnesium, and contents of nutrients in the leaves, except manganese and iron, were not influenced by the residual effect of the fertilization with sewage sludge.

3. The contents of calcium and magnesium in the soil, pH, sum of bases, effective and potential cation exchange capacity and base saturation percentage increased, while effective acidity decreased, with the increment in the residual doses of sewage sludge.

4. The contents of manganese and iron in leaf tissues decreased with the increment in the residual doses of sewage sludge.

Acknowledgments

The authors thank FAPEMIG and CNPq, for the financial support, which allowed the conduction of this research

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Publication Dates

  • Publication in this collection
    Oct 2015

History

  • Accepted
    24 Apr 2015
Unidade Acadêmica de Engenharia Agrícola Unidade Acadêmica de Engenharia Agrícola, UFCG, Av. Aprígio Veloso 882, Bodocongó, Bloco CM, 1º andar, CEP 58429-140, Tel. +55 83 2101 1056 - Campina Grande - PB - Brazil
E-mail: revistagriambi@gmail.com