Soil pollution under orchards in central-eastern Portugal: sources, risks and potential solutions

Pesticide residues and microplastics are important contaminants of agricultural soil, with the potential to interact with each other. This thesis focused on investigating the distribution and effects of these contaminants using peach orchards from central-eastern Portugal as case study sites. Additionally, it evaluated cover crops as an alternative to herbicides and examined the remediation effects of biochar. The results showed that glyphosate and aminomethylphosphonic acid (AMPA) were the pesticide residues present in soil at the highest concentrations. Microplastics were found in the soil of all orchards and irrigation water was identified as their major source. Biochar accelerated glyphosate dissipation in soil. However, it had the opposite effect on acetamiprid, difenoconazole, flonicamid, and pyriproxyfen. As a replacement of herbicides, cover crops contributed to a significant reduction in soil contamination by glyphosate and AMPA without negatively affecting yield or fruit quality.