Abstract
ABSTRACT Although it is known that alkalinized sewage sludge raises the pH of acid soils, there is limited knowledge regarding its effects on other soil fertility indicators, such as P and K availability and soil organic C content. Thus, the goal of this study was to evaluate how the application of alkalinized sewage sludge affects the fertility of acid soil. Twenty sewage treatment plants were selected throughout Paraná State (Brazil), and samples of alkalinized sewage sludge and samples of the most representative agricultural soil of the region were collected (covering soils with medium, clayey or very clayey texture). Each soil was incubated for 60 days with doses of sewage sludge (0, 10, 20, 40, and 80 Mg ha-1) from its region and equivalent doses of limestone. The alkalinized sewage sludge was superior to limestone in the correction of soil acidity (pH, Al3+, and H + Al3+) and P and Ca2+ availability. The sludge also increased Mg2+ availability in all soils, K+ in seven soils and organic C in three soils. The very clayey soils (higher buffering capacity) supported higher sludge doses than did clayey and medium texture soils. The alkalinized sewage sludge application in acid soils proved to be an interesting alternative to recycling this type of waste, because it improved soil fertility and could reduce costs associated with soil management and crop fertilization.
Highlights
The application of sewage sludge to agricultural soils is one strategy used to recycle this type of waste
One of these treatments is prolonged alkaline stabilization (PAS), the principle of which is the elimination of pathogens by increasing the pH of the sludge to levels equal to or greater than 12, which is accomplished by the addition of CaO or CaO + MgO (Bittencourt et al, 2014)
The increase in the pH-CaCl2 of the soils treated with alkalinized sewage sludge (Figure 2A) was consistent with previous studies using this type of sludge (Corrêa et al, 2007; Tamanini et al, 2008; Serrat et al, 2011) or other alkaline organic residues (Pértile et al, 2012; Neto et al, 2016)
Summary
The application of sewage sludge to agricultural soils is one strategy used to recycle this type of waste. Regardless of the final destination, the sludge goes through processes or treatments to ensure that this residue is not a source of pathogens One of these treatments is prolonged alkaline stabilization (PAS), the principle of which is the elimination of pathogens by increasing the pH of the sludge to levels equal to or greater than 12, which is accomplished by the addition of CaO or CaO + MgO (Bittencourt et al, 2014). In countries such as Brazil, the United States, Canada, Turkey, Ireland, and South Africa, prolonged alkalization is one of the methods used to sanitize sewage sludge (LeBlanc; Matthews; Richard, 2008; Healy et al, 2016)
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