# Linking Soil Microbial Diversity to Nitrogen and Phosphorus Dynamics

## TL;DR

This study examines how soil autoclaving affects microbial activity and the dynamics of nitrogen and phosphorus in soil.

## Contribution

The study introduces a novel method using 14C-glucose and 33P to evaluate the impact of soil autoclaving on microbial activity and nutrient dynamics.

## Key findings

- Soil autoclaving eliminates microbial activity, but reinoculation with diluted suspensions increases CO2 respiration.
- Autoclaving increases ammonium levels and decreases nitrate levels in soil.
- Autoclaving reduces phosphorus lability regardless of microbial reinoculation.

## Abstract

Changes in the soil microbial community for studies of different novel communities can be promoted by different methodologies, among which soil autoclaving stands out as a quick and readily available tool. However, this procedure may also directly or indirectly alter nitrogen (N) and phosphorus (P) dynamics. The purposes of this study were as follows: (i) to characterize microbial activity after soil autoclaving through microbial 14CO2-respiration; and (ii) to evaluate the effect of microbial manipulation and autoclaving on soil N and 33P dynamics. For this, two sets of soil samples from two areas (forest and cultivated area) were used in the laboratory. Firstly, 14C-glucose was added to the soils and after 24 h five soil microbiomes were generated: AS (autoclaved soil), and AS re-inoculated with serial dilutions (w/v) prepared by successive mixing of soil suspensions in sterile deionized water obtaining 10−1, 10−3, and 10−6, which generated the treatments AS + 10−1, AS + 10−3, and AS + 10−6; and the treatment NS (non-autoclaved control), all incubated for 28 d. 14CO2 emission was used to characterize microbial activity; additionally, N dynamics were assessed at the end of incubation. In a second assay, 33P was applied to the soil before autoclaving and re-inoculation. Following further incubation (14 d), a 33P chemical fractionation was performed. The following are based on the results: (i) 14CO2 emission: microbial activity in the autoclaved soil is null, but after a reinoculation of AS + 10−1 and AS + 10−3 soil dilution suspension, the 14CO2-respiration is higher than in an NS. (ii) regarding the N dynamics, in autoclaved soils, the microbial levels increased N-NH4+ concentration, with an evident increase in the AS + 10−3 and AS + 10−1, and a reduction in the N-NO3− concentration in comparison to the NS. For 33P, the autoclaving procedure itself reduced the 33P lability, regardless of the levels of microbial community reinoculated.