• Allison, L E 1965 Organic carbon.In Methods of Soil Analysis, part 1. Monograph No. 9. Madison, Wisconsin.

• Bouyoucos G J 1936 Directions for making mechanical analysis of soils by hydrometer method. Soil Sci. 42, 225-229.

  CAS  Google Scholar 

• Bray R H and Kurtz L T 1945 Determination of total organic and available forms of phosphorus in soils. Soil Sci. 59, 39-45.

  CAS  Google Scholar 

• Campbell I B, Claridge G G C and Blackmore L C 1978 Pedological study of soils from basaltic parent material on the island of Atiu, Cook Island. New Zealand J. Soil Sci. 21, 229-248.

  CAS  Google Scholar 

• Clarke A L, Greenland D J and Quirk J P 1967 Changes in some physical properties of the surface of an impoverished Red-Brown earth under pasture. Austr. J. Soil Sci. Res. 5, 59-68.

  Article  Google Scholar 

• Greenland D J and Lal R (Eds) 1977 Soil Conservation and Management in the Humid Tropics. J. Wiley and Sons Inc., New York.

  Google Scholar 

• Food and Agriculture Organization 1984 Physical and Chemical Methods of Soil and Water Analysis. FAO, Rome.

  Google Scholar 

• Food and Agriculture Organization 1990 An International Action Programme onWater and Sustainable Agricultural Development. FAO, Rome.

  Google Scholar 

• Hamblin A P and Greenland D J 1977 Effects of organic constituents and complexed metal ion on aggregate stability of some East Anglian Soils. J. Soil Sci. 28, 410-416.

  CAS  Google Scholar 

• Harris R F, Chesters G and Allen O N 1996 Dynamics of soil aggregation.In N C Brady (Ed.) Advances in Agronomy 18, 107-169.

• Jackson M L 1958 Soil Chemical Analysis: An Advanced Course. University of Wisconsin, Madison, USA.

  Google Scholar 

• Juo A S R and Lal R 1977 The effects of fallow and continuous cultivation on the chemical and physical properties of an Alfisol in Western Nigeria. Plant Soil 47, 567-584.

  Article CAS  Google Scholar 

• Juo A S R and Payne W A 1993 Management of Organic Matter for Sustained Food Production in the Tropics. FAO, Rome.

  Google Scholar 

• Klute A 1965 Laboratory measurement of hydraulic conductivity of saturated soils.In Methods of Soil Analysis, part 1. Monograph No. 9. Madison, Wisconsin.

• Kowal J M and Kassam A H 1978 Agricultural Ecology of Savannah. Oxford. Clarendon Press. 403 pp.

  Google Scholar 

• Lal R, Wilson, G F and Okigbo B N 1979 Changes in properties of an Alfisol produced by various crop covers. Soil Sci. 127, 377-382.

  Article CAS  Google Scholar 

• Martin W S 1944 Grass covers in relation to soil structure. The Empire J. Exp. Agric. 12, 21-32.

  CAS  Google Scholar 

• McBride T P (Ed.) 1990 TropSoils Technical Report 1988-1989. North Carolina State University, Raleigh, NC, USA. 357 pp.

  Google Scholar 

• Obi M E 1982 Runoff and soil loss from an Oxisol in southeastern Nigeria under various management practices. Agric. Water Manage. 5, 193-203.

  Article  Google Scholar 

• Obi M E and Nnabude P C 1988 The effects of different management practices on the physical properties of a sandy loam soil in southeastern Nigeria. Soil Tillage Res. 12, 81-90.

  Article  Google Scholar 

• Obi M E and Salako F K 1995 Rainfall parameters influencing erosivity in southeastern Nigeria. Catena. 24, 275-287.

  Article  Google Scholar 

• President's Science Advisory Committee 1967 The World Food Problem, Vol. 2. The White House, Washington DC, USA.

  Google Scholar 

• USDA Soil Survey Staff 1975 Soil Taxonomy. Agriculture Handbook 436. Soil Conserv. Service. Washington DC.

  Google Scholar 

• Vomocil J A 1965 Porosity.In Methods of Soil Analysis, part 1. Monograph No. 9. Madison, Wisconsin.

• Wilkinson G E 1975 Effects of grass fallow rotations on infiltration of water into savanna zone soil of Nigeria. Tropical Agric. 52, 97-103.

  Google Scholar 

• Wilkinson G E and Aina P O 1976 Infiltration of water into two Nigerian soils under secondary forest and subsequent arable cropping. Geoderma 15, 51-59.

  Article  Google Scholar 

• Wilson G F, Lal R and Okigbo B N 1982 Effects of cover crops on soil structure and yield of subsequent arable crops grown under strip tillage on an eroded Alfisol. Soil Tillage Res. 2, 233-250.

  Article  Google Scholar 

• Woomer P L and Swift M J 1994 The Biological Management of Tropical Soil Fertility. J. Wiley and Sons Ltd., Chichester.

  Google Scholar 

• Yoder R E 1936 A direct method of aggregate analysis of soils and a study of the physical nature of erosion losses. J. Am. Soc. Agron. 28, 337-351.

  CAS  Google Scholar 

• Young A 1989 Agroforestry for Soil Conservation. CAB International, Wallingford, UK. 276 pp.

  Google Scholar 

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