Long-term sewage sludge application in a tropical Oxisol: Effects on acidity and availability of micronutrientes

Mariângela B Freiberger,Leonardo T Büll,Fabiano G Silva,Silvia Capuani,Gustavo Castoldi,Diego O Ribeiro

doi:10.1590/1807-1929/agriambi.v24n6p402-408

Mariângela B Freiberger, Leonardo T Büll + Show 4 more

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https://doi.org/10.1590/1807-1929/agriambi.v24n6p402-408

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Abstract

ABSTRACT The objective of this study was to evaluate the effects of acidity and availability of micronutrients on a sandy clay loam Oxisol grown with soybeans (summer) and black oat (autumn/winter), after long-term applications of biodigested sewage sludge (BS) and centrifuged sewage sludge (CS). The experiment was conducted in Botucatu, SP, Brazil, from 2002 to 2014, using a randomized block design, in 2×4 factorial scheme, with four repetitions. Treatments corresponded to six biennial applications of BS and CS at four doses: 0, 2, 4 and 8 Mg ha-1 (dry basis). Soil samples up to 0.60 m depth were taken after twelve years, and pH, potential acidity, exchangeable acidity and micronutrient contents were evaluated. The CS applications of 4 and 8 Mg ha-1 led to pH values within the recommended range up to depths of 0.10 and 0.20 m, respectively, whereas BS applications did not result in adequate pH values in any layer. The increased soil pH caused by CS applications resulted in a proportional reduction in soil potential acidity, whereas BS applications resulted in high value of potential acidity (70 mmolc dm-3) in all layers. The CS applications resulted in low Al3+ concentrations up to 0.20 m depth, whereas BS applications led to high Al3+ concentrations from the 0.05-0.10 m layer. The successive applications of both sludges resulted in Cu2+, Fe2+, Mn2+ and Zn2+ concentrations that exceeded the maximum values allowed in all soil layers. Low boron concentrations were found in the soil, and pH was the determinant factor for it.

Highlights

The high costs of commercial fertilizers and increase in environmental pollution make the use of sewage sludge in agriculture an attractive option, from both the economic and environmental points of view, because of the cycling of nutrients (Santos et al, 2011)
In the first three layers, the interaction between factors was significant for soil pH (Figures 1A, B and C) and the data fitted to increasing linear equations
The highest dose of centrifuged sewage sludge (CS) led to pH values that were 38, 41 and 39% higher than those caused by the same dose of biodigested sewage sludge (BS) in the three layers, respectively

Summary

Introduction

The high costs of commercial fertilizers and increase in environmental pollution make the use of sewage sludge in agriculture an attractive option, from both the economic and environmental points of view, because of the cycling of nutrients (Santos et al, 2011). Corrêa et al (2009b) reported that the superficial application of centrifuged sewage sludge in an Oxisol resulted in the correction of soil acidity, causing displacement of Ca2+, increase of pH and reduction of Al3+ up to 0.40 m depth. Pigozzo et al (2008) observed that sewage sludge application caused an increase in Fe, Mn, Cu, Zn concentrations and in CEC, besides reduction of pH in an Oxisol (0-0.20 m). The present study aimed to evaluate micronutrients concentrations, pH, potential acidity and exchangeable acidity after 12 years of biennial applications of centrifuged sewage sludge and biodigested sewage sludge

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