D. C. Clay, V. Kelly, E. Mpyisi and T. Readon, “Input use and Conservation Investments and Determinants,” In: C. B. Barrett, F. Place and A. A. Aboud, Eds., Natural Resource Management in African Agriculture: Understanding and Improving Current Practices, CABI Publishing, Oxon and New York, 2002, pp. 103-114.
 M. E. Lopez-Masquera, F. Cabaleiro, M. S. Sainz, A. Lopez-Fabal and E. Carral, “Fertilizing Value of Boiler Litter: Effect of Drying and Palletizing,” Bioresource Tech-nology, Vol. 99, No. 13, 2008, pp. 5626-5633. doi:10.1016/j.biortech.2007.10.034
 P. R. Warman, “The Effect of Fertilizer, Chicken Manure on Timothy Yield, Tissue, Composition and Soil Fertility,” Agric Wastes, Vol. 18, No. 4, 1986, pp. 289-298. doi:10.1016/0141-4607(86)90074-0
 A. Mehlich, “Mehlich 3 Soil Extractant: A Modification of Mehlich 2 Extractant,” Communications in Soil Science and Plant Analysis, Vol. 15, No. 12, 1984, pp. 1409- 1416. doi:10.1080/00103628409367568
 W. Van Lierop, “Determination of Available Phosphorus in Acid and Calcareous Soils with Kelowna Multiple- Element Extractant,” Soil Science, Vol. 146, No. 4, 1988, pp. 284-291. doi:10.1097/00010694-198810000-00009
 M. L. Self-Davis, P. A. Moore and B. C. Joern, “Determination of Water or Dilute Salt-Extractable Phosphorus in Soils,” In: G. M. Pierzynski, Ed., Methods of Phosphorus Analysis for Soils, Sediments, Residuals, and Waters, Kansas State University, Manhattan, 2000, pp. 24- 24.
 M. Zhou and Y. Li, “Phosphorus Sorption Characteristics of Calcareous Soils and Limestone from the Southern Everglades and Adjacent Farmlands,” Soil Science Society of America Journal, Vol. 65, No. 5, 2001, pp. 1404- 1412. doi:10.2136/sssaj2001.6551404x
 A. N. Sharpley, J. L. Weld, D. B. Beegle, P. J. A. Kleinman, W. J. Gburek, P. A. Jr. Moor and G. Mullins, “Development of Phosphorus Indices for Nutrient Management Planning Strategies in the United States,” Journal of Soil and Water Conservation, Vol. 58, No. 3, 2003, pp. 137-152.
 J. T. Sims, “Soil Test Phosphorus: Olsen P,” In: G. M. Pierzynski, Ed., Methods for Phosphorus Analysis for Soils, Sediments, Residuals and Water, Kansas State University, Manhttan, 2000, pp. 20-21.
 R. W. McDowell and A. N. Sharpley, “Phosphorus Losses in Subsurface Flow Bfore and after Manure Application to Intensively Farmed Land,” Science of the Total Environment, Vol. 278, No. 1-3, 2001, pp. 113-125. doi:10.1016/S0048-9697(00)00891-3
 J. L. McCoy, L. J. Sikora and R. R. Weil, “Plant Availability of Phosphorus in Sewage Sludge Compost,” Journal of Environmental Quality, Vol. 15, No. 4, 1986, pp. 403-409. doi:10.2134/jeq1986.00472425001500040016x
 H. Tunney and B. Pommel, “Phosphorus Uptake by Ryegrass from Monocalcium Phosphate and Pig Manure on Two Soils in Pots,” Irish Journal of Agricultural & Food Research, Vol. 26, No. 2-3, 1987, pp. 189-198.
 P. M. Gale, M. D. Muller, C. Cieslik, D. D. Tyle, B. N. Duck, M. Kirchner and J. McClure, “Phosphorus distribution and Availability in Response to Diary Manure Applications,” Communications in Soil Science and Plant Analysis, Vol. 31, No. 5-6, 2000, pp. 553-565. doi:10.1080/00103620009370459
 A. Walkley and I. A. Black, “An Examination of Degtjareff Method for Determining Soil Organic Matter and a Proposed Modification of the Chromic Acid Titration Method,” Soil Science, Vol. 37, No. 1, 1934, pp. 29-38. doi:10.1097/00010694-193401000-00003
 O. O. Akinremi, N. Armisen, M. A. Kashem and H. H. Janzen, “Evaluation of Analytical Methods for Total Phosphorus in Organic Amendments,” Communications in Soil Science and Plant Analysis, Vol. 34, No. 19-20, 2003, pp.2981-2991.doi:10.1081/CSS-120025220
 J. Murphy and J. P. Riley, “A Modified Single Solution Methods for the Determination of Available Phosphate in Natural Water,” Acta Analytica, Vol. 27, 1962, pp. 31-36. doi:10.1016/S0003-2670(00)88444-5
 M. A. Kashem, O. O. Akinremi and O. J. Racz, “Phosphorus Fractions in Soil Amended with Organic and Inorganic Phosphorus Sources,” Canadian Journal of Soil Science, Vol. 84, No. 1, 2004, pp. 83-90. doi:10.4141/S03-018
 G. J. Racz and R. J. Soper, “Reaction Products of Orthophosphates in Soils Containing Varying Amounts of Calcium and Magnesium,” Canadian Journal of Soil Science, Vol. 47, No. 3, 1967, pp. 223-230. doi:10.4141/cjss67-035
 M .A. Kashem, O. O. Akinremi and G. J. Racz, “Extractable Phosphorus in Soil Amended with High Rates of Organic Amendments,” Canadian Journal of Soil Science, Vol. 84, No. 4, 2004, pp. 459-467. doi:10.4141/S03-085
 M. Zhang, R. Wright, D. Heaney and D. Vanderwel, “Comparison of Different Phosphorus Extraction and Determination Methods Using Manured Soils,” Canadian Journal of Soil Science, Vol. 84, No. 4, 2004, pp. 469-475. doi:10.4141/S02-023