Evaluating potentially toxic elements under prolonged application of pig manure in Brazilian soils

Abstract Pig manure (PM) is crucial for animal protein production, especially in Brazil, where pork is widely consumed. However, managing animal waste remains a challenge. While PM serves as a soil amendment, it may also introduce potentially toxic elements (PTEs), such as heavy metals, into agricultural soils. Few studies address the impact of long-term PM application on the availability of these metals at various soil depths. This study analysed copper (Cu), zinc (Zn), iron (Fe), manganese (Mn), cadmium (Cd), and lead (Pb) in soils with prolonged PM use in Florestal (FL), Pará de Minas (PDM), and São José da Varginha (SJV), Brazil. Samples were collected from six soil depths using the Mehlich-1 method, with element concentrations determined via atomic absorption spectrophotometry. Data were analysed using ANOVA and Duncan’s test (5% probability). The results showed that soils with PM had higher levels of Cu and Zn, with Cd elevated only in PDM. Fe and Mn showed no significant differences, whilst Pb was higher in FL and PDM soils without PM. PM application increased Cu and Zn levels but did not significantly affect the other elements. In conclusion, long-term PM use elevates Cu and Zn levels in soils, posing potential risks of Zn toxicity. Public policies are needed to regulate PM usage, reduce soil pollution, and promote sustainable waste management for environmental health.