Muhammad, A., Dikko, A., Audu, M., & Singh, A. (2011). Comparative Effects of Cowpea and Soybean Genotypes on N<sub>2</sub> - Fixation and N-Balance in Sokoto Dry Sub-Humid Agro-Ecological Zone of Nigeria. Nigerian Journal of Basic and Applied Sciences, 18(2). https://doi.org/10.4314/njbas.v18i2.64346