Biochar use for reducing agrochemical leaching in tropical agricultural soils

Abstract

Biochar amendments to soils have sparked remarkable research interests in agricultural and environmental sustainability. However, limited studies have focused on the use of biochar for reducing agrochemical leaching in tropical soils. Also, limited studies have focused on understanding agricultural stakeholders’ perspectives on biochar use, which are essential for the development of its implementation. This thesis aims to: (i) devise a stakeholder analysis for implementing biochar in agricultural systems of Belize; (ii) use laboratory approaches to identify biochars that reduce agrochemical leaching in tropical soils; and (iii) apply a groundwater pesticide-fate model to simulate biochar-amended soils and predict its effects on pesticide concentrations in groundwater. A mixed-method design consisting of thematic and descriptive analyses were used to understand the perspectives of Belizean agricultural stakeholders. Batch and column leaching studies were performed to analyse leachate agrochemicals using analytical methods such as High-Performance Liquid Chromatography and Liquid Chromatography-Mass Spectrometry. Standard scenarios of the PEARL pesticide-fate model, used to predict concentrations of pesticides in groundwater, were modified to simulate the leaching of pesticides in biocharamended soils. Results from the stakeholder analysis showed that biochar could be implemented in Belize if major challenges in its agricultural sector are resolved. These challenges include agricultural research and education advances, funding availability and collaboration amongst agricultural stakeholders. Also, laboratory experiments and pesticide fate model showed that tropical soils amended with rice husk biochar were able to decrease the leaching of agrochemicals in groundwater. These results are noteworthy mainly since atrazine, although being banned in the European Union due to its tendency and persistency to contaminate groundwater is still widely used in tropical agricultural soils that are vulnerable to agrochemical leaching. Biochar use offers an excellent opportunity for agricultural stakeholders to reduce agrochemical leaching in tropical agricultural soils