Effects of Biochar, Poultry Manure and Their Mixture on Essential Nutrients of Sweet Potato Leaves and Storage Roots in Degraded Tropical Alfisols of Southwest Nigeria.

Essential nutrient concentrations in edible portions of crops can affect human health. Hence, field experiments were carried out for two growing seasons (2019 and 2020) at two degraded sites using a randomized complete block design in a factorial layout with three replications to evaluate the effects of biochar (B), poultry manure (PM), and their combined application on leaf nutrient concentrations and mineral composition of sweet potato. Each year, the experiment consisted of 4 × 3 factorial combinations of biochar (0, 10.0, 20.0, and 30.0 t ha−1) and poultry manure (0, 5.0 and 10.0 t ha−1). The results showed that the sole application of B and PM and their combined application, improved sweet potato leaf nutrient concentrations and mineral composition of sweet potato storage roots. In both years, there were significant interactions of B and PM (B × PM) on leaf nutrient concentrations and mineral composition of sweet potato that were determined, indicating the potential of B in enhancing PM use efficiency and improving better use of the nutrients in the PM. It was found that the highest dosage of combination of 30.0 t ha−1 B and 10.0 t ha−1 PM (B30+ PM10) gave the highest leaf nutrient concentrations and mineral composition of sweet potato at both sites. Lowest leaf nutrient concentrations and mineral composition was obtained for the control. The study indicated that B in combination with PM have the potential to improve sweet potato leaf nutrient concentrations and mineral composition of sweet potato storage roots for human health in severely degraded soils. [ABSTRACT FROM AUTHOR]