1. Ahmad, R., Khalid, A., Arshad, M., Zahir, Z.A., & Naveed, M. (2006). Effect of raw (un-composted) and composted organic waste material on growth and yield of maize (Zea mays L.). Soil Environment, 25 (2), 135– 142.
2. Akande, M.O., Adediran, J.A., & Oluwatohinbo, F.I. (2005). Effects of rock phosphate amended with poultry manure on soil available P and yield of maize and cowpea. African Journal of Biotechnology, 4(5), 444–448.
3. Redistribution and persistence of microorganisms and steroid hormones after soil-injection of swine slurry
4. Soil Microbial Activity in Conventional and Organic Agricultural Systems
5. Brady, N.C., & Weil, R.R. (2015). Soil Phosphorus and Potassium. The Nature and Property of Soils, 671-716.