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DIVISION S-8-NUTRIENT MANAGEMENT & SOIL & PLANT ANALYSIS

Soil Characteristics and Management Effects on Phosphorus Sorption by Highland Plateau Soils of Ethiopia

^a Dep. of Soil Science, North Carolina State Univ., Box 7619, Raleigh, NC 27695-7619 USA

wayne_robarge{at}ncsu.edu

Differences in crop and fertilizer management are known to influence P retention by soils. An experiment was conducted to study the effect of soil characteristics and management practices on P sorptoin behavior of the highland plateau soils of Ethiopia. Surface samples from two Vertisols, an Andisol, and an Alfisol were collected from farmers' fields, research station farms, and from non-cultivated-non-fertilized areas. Phosphorus sorption data were obtained by equilibrating 3-g soil samples in 30 mL of 0.01 M CaCl₂ containing various amounts of KH₂PO₄. Inorganic P fractions were determined by the Hedley P fractionation scheme. There was little variation in P sorption among Vertisol samples of alluvial origin as a result of cultivation-fertilization practices. For soils of volcanic origin (Vertisol2 and Andisols), and the Alfisol, samples collected from farmers' fields sorbed more P than the non-cultivated and research station samples. Least amounts of applied P sorbed by the non-cultivated Andisol samples reflect the relatively large amounts of resin extractable P initially present in these soils and demonstrate that labile P initially present in the soil can influence subsequent P sorption. Stepwise regression analysis of the P sorption data showed that resin P accounts for 81% of the variation in P sorption at 0.2 mg P L^-1 in solution. The highest amount of P was sorbed by samples collected from farmers' fields and was mainly due to the practice of continuous cropping with minimal P fertilization, which depletes labile P, and therefore requires higher levels of P fertilization for optimum crop yield.

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				B. L. Allen and A. P. Mallarino Relationships between Extractable Soil Phosphorus and Phosphorus Saturation after Long-Term Fertilizer or Manure Application Soil Sci. Soc. Am. J., February 2, 2006; 70(2): 454 - 463. [Abstract] [Full Text] [PDF]