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NUTRIENT MANAGEMENT & SOIL & PLANT ANALYSIS

Phosphorus Sorption as Affected by Soil Properties and Termite Activity in Eastern and Southern Africa

Dep. of Agronomy and Horticulture, Univ. of Nebraska, Lincoln, NE 68583

^* Corresponding Author (mmamo3{at}unl.edu).

Phosphorus is often the limiting nutrient to crop production in eastern Africa. Efficient management of P requires an understanding of the factors affecting availability of soil native P and applied fertilizer P. The objectives of this study were (i) to evaluate the relationships between soil properties and P sorption characteristics, and (ii) to assess the effect of termite activities on soil properties and P sorption characteristics. Phosphorus sorption isotherms were determined for 36 soils, including 7 samples from termite mounds and surrounding non-termite soils from Uganda and Mozambique. Ammonium-oxalate extractable Al (Al_ox) was the most important property explaining over 90% of the variation in P sorption maximum (S_max) for Uganda and Mozambique soils. However, for the Ethiopia soils 88% of the variation was explained by Mehlich-3 extractable Ca, ammonium-oxalate extractable P (P_ox), and sand content. The S_max of Uganda and Mozambique soils increased by 44 to 390% due to increased clay content from termite activities. The higher S_max of termite mounds implies a greater demand for P fertilizer for low P soils but also a higher P storage capacity and reduced risk of P leaching. Termite mound could be considered as a potential soil amendment.

Abbreviations: Al_ox, ammonium-oxalate extractable aluminum • CCE, calcium carbonate equivalent • Fe_ox, ammonium-oxalate extractable iron • MBC, maximum buffer capacity • OM, organic matter • P_ox, ammonium-oxalate extractable phosphorus • S_max, phosphorus maximum sorption capacity