M.D. Angyu, A.D. Lanki
1Department of Soil Science, Faculty of Agriculture, Federal University Wukari, Taraba State, Nigeria
2Department of Agricultural Technology, College of Agriculture, Science and Technology, Jalingo Taraba State, Nigeria

(Manuscript received 14 August 2024; accepted for publication 22 January 2025)

Abstract. Agricultural wastes are converted into useful products which enhance soil fertility and crop’s yield; hence, reducing environmental pollution. A study was carried out to assess the maturity, phytotoxicity and organic carbon stability of biochar produced from maize cob at 500ºC as well as compost, co-composted biochar and compost + biochar produced using rice straw, dried Melina leaves, fresh mango, eucalyptus leaves and cow manure. Means of the maturity test’s parameter (NH3-N); phytotoxicity parameters such as vigor index, germination index, relative root growth, germination percentage, root length and shoot length; and carbon stability parameters such as hydrogen and hydrogen to organic carbon ratio were compared using Duncan Multiple Range test at p≥ 0.05 probability. The results of the study revealed that compost, co-composted biochar and compost + biochar were adequately matured for soil application having NH3-N less than 75 ppm. Compost had a significantly higher (p≥0.05) germination index (93%) indicating the absence of toxic substances. Organic carbon stability results showed that biochar was the most stable of all the organic amendments in the study due to its least hydrogen to carbon ratio (0.26). Therefore, compost, biochar, co-composted biochar and compost + biochar are apt for soil application with the view to enhancing soil fertility.