Phosphorus sorption on tropical soils with relevance to Earth system model needs

Abstract

Phosphorus (P) availability critically limits the productivity of tropical forests growing on highly weathered, low-P soils. Although efforts to incorporate P into Earth system models (ESMs) provide an opportunity to better estimate tropical forest response to climate change, P sorption dynamics and controls on soil P availability are not well constrained. Here, we measured P and dissolved organic carbon (DOC) sorption isotherms on 23 soils from tropical Oxisol, Ultisol, Inceptisol, Andisol, and Aridisol soils using P concentrations from 10 to 500mg P L−1, and DOC concentrations from 10 to 100mg DOC L−1. Isotherms were fit to the Langmuir equation and parameters were related to soil characteristics. Maximum P sorption capacity (Qmax) was significantly correlated with clay content (ρ=0.658) and aluminium (Al)- or iron (Fe)-oxide concentrations (ρ=0.470 and 0.461 respectively), and the DOC Qmax was correlated with Fe oxides (ρ=0.491). Readily available soil characteristics could eventually be used to estimate Qmax values. Analysis of literature values demonstrated that the maximum initial P concentration added to soils had a significant impact on the resultant Qmax, suggesting that an insufficiently low initial P range could underestimate Qmax. This study improves methods for measuring P Qmax and estimating Qmax in the absence of isotherm analyses and provides key data for use in ESMs.

Bringing function to structure: Root–soil interactions shaping phosphatase activity throughout a soil profile in Puerto Rico

“…In addition to redox, available P can become strongly bound to secondary minerals, essentially unavailable to plants (Walker & Syers, 1976), though some suggest that it could be accessible over longer timescales (Johnson et al., 2003). However, root and microbial production of organic acids can alter soil pH, causing the slow desorption of available P back into the soil solution (Brenner et al., 2019; Kertesz & Frossard, 2014; Yang et al., 2019). These root and microbial functions to capture available P are complemented by the production of phosphomonoesterase enzymes (PME) that increase P availability by accessing the soil organic P pool (McGill & Cole, 1981; Richardson et al, 2009b,2009a; Tarafdar & Claassen, 1988; Turner & Engelbrecht, 2011; Yang & Post, 2011).…”

Too much of a good thing: phosphorus over-fertilisation in rehabilitated landscapes of high biodiversity value

“…Banning et al 2008). Both K and P are immobile nutrients, with P in particular having several mechanisms to bind to colloids, form stable sesquioxides, or transform to a range of organic forms (Sanyal & de Datta 1991;Spain et al 2018;Brenner et al 2019). We have shown that soon after P fertiliser application and after regular application over many years, P remains in the top soil and can be highly stratified (George et al 2006;Ryan et al 2017).…”

Representing methane emissions from wet tropical forest soils using microbial functional groups constrained by soil diffusivity

“…2). The valley soils have approximately 30 % clay and approximately 15 % sand, while the ridge soils have approximately 22 % clay and approximately 30 % sand (Brenner et al, 2019). The soils contain high concentrations of iron (Fe) and aluminum (Al) (oxy)hydroxides where their relative concentrations vary along the catena, and differences in Fe speciation are associated with variable redox conditions Silver, 2013, 2015).…”

“…3). The lower sand and higher clay contents in the valley soils (Brenner et al, 2019), as well as the lower topographic position, likely caused the valley soils to remain wetter than the slope and ridge soils. Therefore, simulated values of gross CH 4 production were fairly stable in the valley soils (Fig.…”