Agronomic potential of biochar prepared from brewery byproducts

This work investigated the effect of biochar produced from brewery byproducts, spent grain and surplus yeast on the physicochemical characteristics of a calcareous loam soil and plant growth of maize (Zea mays L.). Maize is a plant which needs high nitrogen fertilization, while the effect of acidic or neutral biochars on alkaline calcareous soils has only been assessed in a few studies. The effect of biochars on dry weight, as well as the level of macro- and micronutrients in soil, and above- and belowground plant tissues, were investigated, in a 30 day experiment after seedling emergence of maize (Zea mays L.), in the presence and absence of nitrogen fertilization. The results indicated that biochar from organic brewery by-products significantly increased the dry weight of the aboveground part of the plant by 59-186%, relative to the control, without the addition of inorganic N fertilization, and by 46-157% with the addition of inorganic N fertilization. The dry weight of the belowground plant tissues significantly increased by 83-92% and 46-106%, relative to the control, with or without the addition of inorganic N fertilization, respectively. Biochar addition, especially at 5% application rate individually or in a mixture, significantly increased the phosphorus content of plant tissues. The content of potassium in the plants was affected mainly by the addition of biochar derived from surplus yeast, while the concentration of calcium and magnesium in plant tissues was positively affected by spent grain biochar, in absence of inorganic nitrogen fertilization. Addition of biochars produced from brewery byproducts improved soil fertility parameters, particularly the contents of total organic carbon (by 133% and 118% with or without fertilization, respectively), total nitrogen (by 120% and 81% respectively) and available phosphorus in the studied loam calcareous soil. Overall, biochar from brewery wastes showed the potential to enhance plant growth and nutrient availability, thus it is a promising organic fertilizer for sustainable agriculture.