Soil Phosphorous Extraction by Olsen and Double Acid Methods in Acid Soils of Western Kenya
Keywords:
Olsen, phosphorous, double acid, acid soils, extractant.Abstract
Phosphorous is an essential nutrient in plants required for root establishment. In the soil, it is applied as DAP, TSP or phosphate rocks. In acid soils, aluminium and iron are dominant and tend to “fix” phosphorous, making it unavailable for plant uptake. Phosphorous deficiencies are monitored through soil chemical analysis. There are many methods for the extraction of available forms; however, the choice is dependent on several factors among them soil pH. Forty soil samples were collected from three different acid soils in Western Kenya. The samples were air dried, sieved under 2.0 mm sieve and stored in sample bags for subsequent analysis. Phosphorous extraction was carried out using a basic extractant (Olsen bicarbonate method) and acid extractant (double acid method). The extracts were measured colorimetricaly by the ascorbic acid method at 880 nm wavelength. The methods were compared in terms of extracting efficiency, correlations and soil critical levels. The soils had a pH range of between 4.5 – 6.1; phosphorous, 1.66 – 55.37 mg P/ kg by Olsen method and 3.01 – 158.17 mg P /kg by double acid method. The methods were linearly correlated (r = 0.95), however, double acid extracted more phosphorous than Olsen by a factor of 2.67.
References
Holford, I.C.R.(1980), Greenhouse evaluation of four phosphorus soils tests in relation to phosphate buffering and labile phosphate in soils, Soil Sci. Soc. Am. J., 44:555-559.
Kamprath, E.J. and Watson, M.E. (1980), Conventional soil and tissue tests for assessing the phosphorus status of soils. P. 433-469. In:
F.E. Khasawneh et al. (ed.). The role of phosphorus in agriculture. ASA, CSSA and SSSA, Madison, WI.
Kuo, S., Phosphorus. In: Bartels, J.M. and Bigham J.M. (1996). (Eds.) Methods of soil analysis, Part 3. Chemical Methods. SSSA Book Series No. 5, pp 869-920.
Landon, J.R. (1991), Booker Tropical Soils Manual: A handbook for soil survey and agricultural land evaluation in the tropics and subtropics. John Wiley & Sons Inc., New York. pp. 133-137.
Menon, R.G., Hammond, L.L. and Sissingh, H.A. (1988), Determination of plant-available phosphate by the iron hydroxide- impregnated filter paper (Pi) soil test, Soil. Sc. Soc. Am. J.52: 110-115.
Okalebo, J.R., Gathua, K.W. and Woomer, P.C. (2002), Laboratory methods of soil and plant analysis: a working manual. TSBF Programme, Nairobi, pp 36-37.
Olsen, S. R., and Sommers, L.E., Phosphorus. In: Page A. L., Keeney D.R., Baker D.E., Miller R.H., Roscoe Ellis Jr. and Rhoades J.D. (1982). (Eds.) Methods of soil analysis, Part 2. Chemical and Microbiological Properties. Agronomy Monograph No. 9 (Second edition), pp 403-429.
Olsen, S.R., Cole C.V., Watanabe, F.S. and Dean, L.A. (1954), Estimation of Available phosphorus in soils by extraction with sodium bicarbonate USDA Cir. 939 USDA, Washington DC.
Shuman, L.M., Raymer, P.L., Day J.L and Condonnier M.J. (1973). Comparison of four extraction methods on three acid southern east soils. Commun, Soil Sc. Plant Anal. (1988), 19: 579-595.
Thomas, G.W. and Peaslee, D.W., Testing soils for phosphorus. P. 115-132. In: Walsh L.M. and Beaten JD (Eds.). Soil testing and plant analysis. SSSA Book Seer. 3. SSSA, Madison, WI.
Tisdale, S.L and Rucker, D. L. (1964). Crop response to various Phosphates. Tech. Bull. No. 9. The Sulphur Institute, Washington U.S.A.
Yost, R.S., Naderman, G.C., Kamprath and Lobato E. (1982). Availability of rock phosphate measured by acid tolerant pasture grass and extractable phosphorus, Agron. J., 74: 462-468.
