Short-Range-Order Minerals and Dominant Accessory Properties Controlling P Sorption in Tropical Tephra Soils of the Cameroon Volcanic Line

Roger Kogge Enang,Bernard Palmer Kfuban Yerima,Eric Van Ranst,Georges Kogge Kome

doi:10.4236/ojss.2019.98008

Roger Kogge Enang, Bernard Palmer Kfuban Yerima + Show 2 more

Open Access

https://doi.org/10.4236/ojss.2019.98008

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Abstract

Knowledge on soil properties likely to influence P sorption in tephra soils is very important for sustainable management of available P. Sorption studies on six tephra soils were conducted to relate P sorption to soil characteristics in order to identify those with potential influence on P sorption. Four equilibrium-based sorption models commonly encountered in soil studies (Langmuir, Freundlich, Temkin, and Van Huay) were used to describe P sorption in the soils. P sorption was determined by measuring the residual P content of a clarified equilibrating solution of 0.02 N KCl containing varying concentrations (0, 5, 10, 15, 30, 40, 50, 60, 80, and 100 mg/L) of P as KH2PO4 after mixing with 1 g of soil in duplicates for 16 hours at 25°C. Maximum amount of P sorbed for the varying P concentrations used ranged from 2080 to 5402 mg/kg with a potential for greater P sorption maxima at higher P solution concentrations. P sorption in these soils was best described by the Langmuir and Freundlich models. Allophane and ferrihydrite are the principal species controlling the high P sorption in these soils. pH-NaF proved to be a potentially reliable test for assessing the presence of allophanic materials and thus for estimating P sorbed. This work would guide both effective and efficient P fertilizer management with economic implications for both the study area and similar environments.

Highlights

Adsorption is the accumulation of a substance at an interface between the solid surface and the bathing solution [1]
In tephra soils characterized by high organic matter contents and allophanic minerals, this element can become very unavailable as it is adsorbed by the latter
P sorption studies showed that P sorption capacity of the six tephra soils varied from 2080 to 5402 mg/kg

Summary

Introduction

Adsorption is the accumulation of a substance at an interface between the solid surface and the bathing solution [1]. Better still soils with andic soil properties are usually classified as variable charge soils with unique properties that make them respond in a particular manner to different management [3] These soils are known to have a high P-retention capacity thereby posing a problem of P deficiency for crop production; requiring heavy applications of P fertilizers [4]. One common and easiest method usually employed in studying P sorption in soils is the batch method [8] In this method, the solid or adsorbent (soil) is shaken in the solution or adsorbate (e.g., KH2PO4 solution) until the adsorption equilibrium is reached, after which the remaining solute concentration is measured. This is one among many factors that render P sorption studies very challenging and so most often limited to qualitative rather than quantitative appreciation

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