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The role of the soil microbial biomass in plant-nutrient cycling, soil organic matter dynamics and maintenance of soil fertility

Reference	BBS/E/C/00031472
Principal Investigator / Supervisor	Professor Philip Charles Brookes
Co-Investigators / Co-Supervisors
Institution	Rothamsted Research
Department	Rothamsted Research Department
Funding type	Research
Value (£)	101,345
Status	Completed
Type	Institute Project
Start date	01/04/1997
End date	31/03/1999
Duration	24 months

Abstract

The soil microbial biomass is the agent of formation and mineralization of soil organic matter and of the cycling of C, N, P and S in soil. Novel methods to measure this biomass as a single compartment of soil organic matter, the fluxes of nutrients through it and its energetic status in soil (e.g. its adenosine 5' triphosphate content and adenylate energy charge ratio) have been developed and are now used worldwide. Other methods are available to measure soil microbial activity. These include soil organic carbon and nitrogen mineralization, substrate induced respiration, arginine ammonification and dimethyl sulphoxide oxidation. 2 Measurement of the community structure of the biomass (i.e. the fungal and bacterial components) has been achieved using ergosterol as a fungal biomarker, selective inhibition and microscopic techniques. Current major research lines include the role of the soil microbial biomass in soil N dynamics following the incorporation of cereal straw. This is particularly aimed at investigation of factors involved in nitrate leaching. Another is the effects of heavy metals from past sewage sludge applications on soil microbial biomass and microbial activity and long-term implications for soil fertility. 3 The microbial biomass and microbial activity methods have detected changes in soil ecosystem functioning caused by heavy metals at quite small metal concentrations (around one to three times current European Union limits). In particular, `linked' parameters e.g. microbial specific respiration, have been very sucessfully used as `indicators' to detect adverse effects of heavy metals in both field experiments and in non-experimental sites which are metal- contaminated. The newer biomass methodologies can be used to measure microbial biomass and microbial activities in anaerobic soils. This has initiated joint research with Japanese scientists interested in microbial, carbon and nitrogen dynamics in paddy soils. To determine effects of heavy metals on microbial biomass, microbial community structure and microbial activity. (ii) To elucidate survival mechanisms of microbial biomass. (iii) To supervise Italian post-graduate researchers for PhD in microbial/organic matter dynamics. (iv) Kenyan researcher in EU funded project in use of biomass and ATP measurements in Chilean soils, interpretation of results and writing of reports (with K.W.T. Goulding). New research objectives include: 1. Investigate relationships between the chemical, physical and biological properties of organic matter using the technique of thermographic analysis. This seems able to differentiate pools of organic matter of different energy status which can then be linked to predicted differences in metabolic activities of the microbial biomasses developed under different climatic regimes. 2. Evaluate and understand the role of trigger molecules" in changing the biomass from its normal dormant state to a state of high metabolic activity. 2 Microgramme quantities of materials such as various vitamins and plant-soil extracts appear to have enormous stimulatory effects, which fits very well with our theories of microbial survival in soil. These two pieces of work stem from independent collaboration with two groups of Italian scientists. 3. Examine the value of Fatty Acid Methyl Esters (FAMES) as indicators of microbial community structure. The approach has already detected differences in microbial communities from metal-contaminated and non- contaminated soils. Soils under different managements and possibly soil aggregates will now be studied in conjunction with other indicators of microbiological activity. 4. Testing the hypothesis that the problem of P fixation in high-P fixing (African) soils may be decreased by encouraging the formation of and increase in microbial P pools and pools of labile organic P."

Summary

unavailable

Committee	Closed Committee - Agri-food (AF)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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