Effects of Biochar and Poultry Manure Amendments on Soil Physical and Chemical Properties, Growth and Sweet Potato Yield in Degraded Alfisols of Humid Tropics

Information on the impact of biochar and poultry manure on soil characteristics and sweet potato productivity in the humid tropics is lacking. Hence, field experiments were conducted at two locations during the 2019 and 2020 cropping seasons to assess the effects of biochar (B), poultry manure (PM), and their mixture on soil physical and chemical properties, growth and tuber yield of sweet potato (Ipomoea batatas L.) 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 findings revealed that using B and PM alone, as well as in combination, improved soil physical and chemical qualities, as well as sweet potato performance. Significant interactions of B and PM (B × PM) were observed on soil characteristics and sweet potato variables that were measured in both years, showing B’s potential in enhancing PM use efficiency. Pooled over two years, application of the highest dosage of 30.0 t ha-1 B + 10.0 t ha-1 PM significantly increased tuber yield of sweet potato compared with other treatments. The multiple regressions showed that both soil physical (bulk density, porosity and moisture content) and chemical (pH, OC, TN, P, K, Ca, and Mg) properties had a significant impact on sweet potato leaf area and tuber yield. The findings indicated that B and PM have the ability to improve soil quality and sweet potato production. Keywords: Biochar; Poultry manure; Soil properties; Sweet potato; Alfisols