Microbial responses to P addition in six South African forest soils

Abstract

Forests growing on highly weathered soils are often phosphorus (P) limited and competition between geochemical and biological sinks affects their soil P dynamics. In an attempt to elucidate the factors controlling the relative importance of these two sinks, we investigated the relationship of between soil microbial growth kinetics and soil chemical properties following amendments with C, N and P in six South African forest soils. Microbial growth kinetics were determined from respiration curves derived from measurements of CO(2) effluxes from soil samples in laboratory incubations. We found that microbial growth rates after C + N additions were positively related to NaOH-extractable P and decreased with soil depth, whereas the lag time (the time between substrate addition and exponential growth) was negatively related to extractable P. However, the growth rate and lag time were unrelated to the soil's sorption properties or Al and Fe contents. Our results indicate that at least some of the NaOH-extractable inorganic P may be biologically available within a relatively short time (days to weeks) and might be more labile than previously thought. Our results also show that microbial utilization of C + N only seemed to be constrained by P in the deeper part of the soil profiles.

Keywords

Phosphorus availability; Microbial bioassay; Weathered soils; Soil respiration; Microbial growth rate; Hedley fractionation

Published in

Plant and Soil
2010, volume: 329, number: 1-2, pages: 209-225
Publisher: SPRINGER

SLU Authors

• Ilstedt, Ulrik

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Environmental Sciences and Nature Conservation

Publication identifier

• DOI: https://doi.org/10.1007/s11104-009-0146-3

Permanent link to this page (URI)

https://res.slu.se/id/publ/60001