Manure-Derived Biochars for Use as a Phosphorus Fertilizer in Cotton Production

Biochars made from animal manure feedstock appear to be a potential phosphorus (P) fertilizer source. Five different manure-derived biochars, pyrolyzed at two different temperatures (350 and 700 °C) were assessed for their potential as a P fertilizer for cotton (Gossypium hirsutum L.). A greenhouse study was conducted using a Uchee sand soil. Biochar was applied at rates that provided 40 mg P kg-1 soil. Four rates of calcium phosphate (0, 20, 40, and 60 mg P kg-1 soil) were included in the study. Cotton plants were allowed to grow to 60 days post-emergence at which point leaves and stems were harvested for physical and chemical analysis. The experiment was conducted twice. Results demonstrated that biochar worked as a P fertilizer and that feedstock choice combined with biochar processing temperature accounted for a majority of the differences among the 10 treatments tested. When applied at standard P fertilization rates, manure-derived biochars perform equally to calcium phosphate fertilizer.