Group leader - Soil Microbial Ecologist
e-mail: philip.brookes@bbsrc.ac.uk
Phil has been working on aspects of soil microbial biomass since about 1978. The microbial biomass treats the soil micro-organisms as a single unit, or 'black box' rather than studying individual micro-organisms. A good analogy is that we are studying the forest rather than an individual tree.
The biomass concept and methodology were based on pioneering work of Professors David Jenkinson and Powlson at Rothamsted. The original method involved a bioassay, when the biomass, after killing in situ by CHCl3 fumigation, was partially mineralised and the mineralised components measured and calibrated (termed Fumigation Incubation or FI) to estimate the initial biomass. Phil later worked with both David Jenkinson and David Powlson to produce the next 'generation' of biomass methods, termed Fumigation Extraction or FE. Here, the cells of the microbial biomass are again treated in situ with CHCl3 to lyse them. However, instead of an incubation step the lysed biomass is partially extracted with simple salt solutions and measured by chemical analysis. The FE method has now entirely superseded FI in biomass methodology. Full details of our biomass methods are to be found elsewhere on our website. Our FE method for measuring biomass C is currently the most widely cited paper in Soil Biology and Biochemistry [Vance E. D., Brookes P. C. and Jenkinson D.S (1987) An extraction method for measuring soil microbial biomass C].
The biomass methods have been found to have a vast number of applications. Examples include soil organic C, N, P and S dynamics, crop residue incorporation, as an indicator or 'early warning' of changing soil conditions, effects of heavy metals from sewage sludge, and biocides, on soil microbial processes, modelling of soil organic matter dynamics etc. Other work has focussed on more fundamental work such as the evolutionary adaptations of the biomass which equip it for survival in the soil environment.
Phil also has an interest in soil phosphate chemistry, particularly linked to the leaching of soil phosphorus from soil to water. He and his group demonstrated that, totally in contrast to current perception, environmentally significant amounts of soil P were leaching through P unsaturated subsoils, in the Broadbalk Continuous Wheat Experiment. This work led to the concept of the 'Change Point, the soil P concentration at which significant quantities of P begin to move from soil to water. This 'Change point ' varies in different soils, in ways which we do not yet fully understand, other than it is correlated with soil exchangeable Al and % soil organic C. However it is always many times smaller that soil P saturation concentrations and in most soils, is at or larger than the soil P concentration required for maximum yields.
Other work to increase P availabilty in small farms is ongoing in SubSaharan in conjunction with The Kenyan Agricultural Research Institute. Even if fertilizer P is available, in many soils it is ineffective because they fix P so that it is unavailable to plants. However, Phil and his African colleagues showed that fertilizer P applied with small amounts of farmyard manure gave much improved yields of maize than either when applied alone. It seems that the manure stimulates the growth of the biomass, which, in turn, immobilises fertilizer P, which would otherwise have been fixes by the soil colloids and lost to the plants. This P is then slowly released from the biomass to the plants during the process of biomass turnover.
Areas of expertise
Microbial biomass and activity
Soil organic C and N
Microbial activity
Soil quality
ATP and adenylate energy charge
Phosphate leaching from soil to water.
Soil and fertilizer phosphate in SubSaharan agriculture.
Qualifications
BSc (Ist Class Hons.) PhD, DSc from Coventry University.
Visiting Professor of Soil Science at Coventry University.
Honorary Professor at Institute of Sub-Tropical Agriculture, Changsha, China
Honorary Professor at North West University, Janling, China.
Honorary Professor at Agricultural University of China, Beijing, China.