Biochar for the Brazilian Cerrado : contributions to soil quality and plant growth

Arenosols (sandy soils) in the Cerrado region of Mato Grosso, Brazil are increasingly used for maize production. These soils are typically nutrient poor with low soil water retention. Since biochar has been shown to improve both nutrient and water retention, this thesis aimed to evaluate biochar effect on physical and chemical properties of a Cerrado Arenosol using four biomass wastes (cotton husks, swine manure, eucalyptus sawmill residue, and sugarcane filtercake) pyrolyzed at three temperatures (400°, 500°, 600°C). These biomass wastes were chosen based on their prevalence in the state of Mato Grosso and their environmental impact. Three greenhouse experiments were carried out with the following objectives: 1) to assess the effects of biochar feedstock type and temperature of pyrolysis on soil water retention; 2) to examine the effect of different biochars on soil nutrients and maize growth applied to soil at different rates, and 3) to observe how different biochar feedstocks and temperatures of pyrolysis affect DOC and NO₃- leaching from a Cerrado Arenosol. All the biochars showed potential to reduce water drainage in the soil compared to the control (no biochar). At application rates 1-4% w/w, filtercake biochar led to the highest mean biomass compared to the other biochars. Eucalyptus biochar did not contribute much to soil fertility, but filtercake biochar led to high soil nutrient concentrations, e.g. Ca, Fe, Mn. Although swine manure biochar was rich in nutrients, low plant biomass in the cotton and swine manure biochar treatments was likely due to higher pH, salinity, and/or excessive water retention. Lastly, DOC and NO₃- concentrations were low in leachate from soils with filtercake and eucalyptus biochars, and high in leachate from soils with cotton and swine manure biochars. This thesis provides an outlook of the agronomic potential of these biochars. Further analyses, such as their effect on soil biological properties, are required to develop well-rounded biochar-soil management practices for Cerrado Arenosols.Science, Faculty ofResources, Environment and Sustainability (IRES), Institute forGraduat