Climatic effects on soil phosphorus pools and availability in sub‐Saharan Africa

Abstract

AbstractPhosphorus (P) is a key limiting nutrient in tropical and subtropical soils but with unknown responses to climate change. We hypothesized that storage and distribution of P pools differ between reference soil groups, but P availability increases with an increase in precipitation in native sub‐Saharan Africa, an underrepresented region in the global P database. To test these hypotheses, we sampled topsoils (0‐10 cm; Arenosols, Lixisols, Acrisols) of uncultivated Savannah woodlands along climate gradients stretching from Mozambique to Zambia. Mean annual precipitation (MAP) ranged from 365 to 1227 mm. We extracted P fractions using Hedley's sequential fractionation, yielding resin‐exchangeable P, P in 0.5M NaHCO3, 0.1M NaOH, 1M HCl, and aqua regia. Extracts were analyzed for total P using inductively coupled plasma–optical emission spectroscopy and inorganic P using the colorimetric molybdenum‐blue method. We found that total P contents were highest in Acrisols (235±76 mg kg‐1), followed by Lixisols (214±45 mg kg‐1) and Arenosols (133±74 mg kg‐1). Beside P storage also P distribution differed between soils. Mean annual temperature (MAT) did not reveal significant correlations to P fractions. However, with increasing MAP, concentrations of almost all P pools increased; available Pi (Resin‐P) increased significantly in Arenosols while potentially bioavailable‐P (NaHCO3‐Po) increased in all soils, with MAP explaining 43% of data variability in Arenosols, 74% Lixisols, and 85% Acrisols. Hence, P availability increased with an increase in MAP to different degrees, i.e., climatic effects on P dynamics were soil‐group specific. Therefore, different regions in the native sub‐Saharan woodlands are thus likely prone to different soil fertility responses when climate changes.This article is protected by copyright. All rights reserved.