Repeated drying and rewetting differently affect abiotic and biotic soil phosphorus (P) dynamics in a sandy soil: A 33P soil incubation study

Emmanuel Frossard,Hao Chen,Astrid Oberson,Klaus A Jarosch,Xiaorong Zhao,Éva Mészáros

doi:10.1016/j.soilbio.2020.108079

Emmanuel Frossard, Hao Chen + Show 4 more

Open Access

https://doi.org/10.1016/j.soilbio.2020.108079

Copy DOI

Abstract

Soil drying and rewetting (DRW) events are expected to occur at higher frequencies because of alterations in climate patterns. Readily extractable inorganic and microbial soil phosphorus (P) pools may be affected due to rapid changes in soil water availability. We aimed to determine how soil P dynamics are affected by repeated soil DRW using a sandy grassland soil that regularly experiences DRW. In a laboratory soil incubation study, the soil was exposed to three DRW cycles, with each cycle consisting of a two-day drying phase, a three-day dryness phase and a four-day moist phase after rapid rewetting. The indicators of abiotic processes (P sorption) and biotic processes (respiration, microbial abundance, potential phosphatase enzyme activities) were regularly determined together with water-extractable P, resin-extractable P and microbial P in a 33P-labelled soil.During the first DRW cycle, microbial P was reduced by half and accompanied by a concomitant but not equivalent increase in water-extractable P and a slight as well as delayed increase in resin-extractable P. Thus, increases in water-extractable P were explained by microbial P released during drying but also by microbial P occupying soil P sorption sites, thereby decreasing soil P sorption. Changes in the 33P-isotopic composition of microbial P at the same time suggested that microorganisms did not respond homogenously to the DRW treatment and indicated an increased mineralisation of previously unavailable organic P compounds. However, during the second and third DRW cycles, only water-extractable P, soil P sorption and potential phosphatase activities were affected by the DRW treatment, whereas all other parameters remained similar in values to the constant moist treatment. The effects of DRW on soil P dynamics appeared to affect water-extractable P more long-lastingly, whereas microbial P and most of the biotic indicators quickly adjusted to the DRW treatment. We conclude that the current concepts suggesting an increased mobility of soil P towards other environmental compartments due to soil DRW should consider that abiotic and biotic soil P dynamics are not equally affected in the case of short repetition of DRW incidences.

Highlights

Drying and rewetting (DRW) of soil is a common natural perturba tion that affects the dynamics of nutrients, such as phosphorus (P), in soil (Blackwell et al, 2010)
For the DRW treatment, only on day 8 (DRW1) we observed a significant increase in resin P (5.8 mg kg− 1), but no differences between CM and DRW were found for other time points
In DRW1, SAmicrobial P already significantly decreased during the moist phase and reached 120 kBq mg− 1 P during soil drying of DRW1, followed by a quick recovery to initial values by rewetting

Summary

Introduction

Drying and rewetting (DRW) of soil is a common natural perturba tion that affects the dynamics of nutrients, such as phosphorus (P), in soil (Blackwell et al, 2010). Soil P dynamics are governed by abiotic and biotic processes. Abiotic processes include the sorption and desorption of P from the soil solid phase and the precipitation and dissolution of P-bearing minerals (Frossard et al, 2000). Biotic processes include the hydrolysis of organic P compounds by phosphatase enzymes and the microbial immobilisation of inorganic or mineralised organic P (Richardson and Simpson, 2011). Microbial biomass represents a relatively small soil P pool, which is usually 0.5%–7.5% of the total P in grassland soils (Oberson and Joner, 2005), microbial P fluxes have been shown to largely dominate gross P fluxes in soils with low inorganic P availability (Bünemann et al, 2012; Schneider et al, 2017). The availability of P for microbial and plant uptake is usually estimated with the amount of water-extractable P or anion exchange resin absorbable P in soil-water suspensions (Yli-Halla et al, 2016)

Objectives

Methods

Results

Discussion

Conclusion