Plastic mulch and pesticide residues in intensive agriculture

In the 1960s, the agricultural “Green Revolution” brough new technologies and heavy mechanisation to the fields. These technologies brought rapid answers to increase the crop yields and improve food security. Among these technologies we found pesticide and plastic mulch applications. Since then the scientific community and the general public became worried of the long term consequences of these short term solutions. Indeed plastic mulch and pesticides leave debris which accumulate in the soil and are potentially harmful to divers organisms. With this PhD thesis we try to encompass the threat posed by plastic mulch and pesticide residues in agriculture. The research was organised in seven different chapters described below.Chapter 1: In introduction we presented the diverse benefices of pesticide and plastic use in agriculture. The many services they provide explained why they are use abundantly worldwide. However both plastic and pesticides have the potential to accumulate in the soil. We narrowed down the focus to plastic mulch as it is used abundantly worldwide and is recognize as an important source of plastic debris. We presented three different plastic types: Low density Polyethylene (LDPE), Pro-oxidant Additive Containing (PAC) and biodegradable (BIO) mulches. Finally, we presented the threats posed by plastic and pesticide residues and the need for more research. We elaborated six main questions that are addressed in the following five research chapters.Chapter 2: The objective of this field assessment was to measure plastic and pesticide residues in agricultural soils and their effects on the soil microbiome. For this, we sampled soil from 18 parcels from 6 vegetable farms in Southeast Spain. The farms were under either organic or conventional management, where plastic mulch had been used for > 25 years. We measured the macro and micro light density plastic debris content, the pesticide residue levels, and a range of physiochemical properties. We also carrie