Relationships between P fractions and the microbial biomass in soils under different land use management

• Published in: Geoderma Vol. 173-174; pp. 274 - 281
• Main Authors: Khan, Khalid Saifullah, Joergensen, Rainer Georg
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2012; Elsevier
• Subjects: Agronomy. Soil science and plant productions; Arable land; Availability; Basaltic soils; Biological and medical sciences; Biomass; clay; Earth sciences; Earth, ocean, space; Exact sciences and technology; Ferralsol; Fumigation; Fundamental and applied biological sciences. Psychology; Geochemistry; Grasslands; land use; microbial biomass; Microbial biomass P; Microorganisms; P-Bray-1; P-Olsen; Polymers; saline sodic soils; Saline-sodic soil; Soil and rock geochemistry; soil organic carbon; Soils; Surficial geology; Asia; Indian Peninsula; Pakistan; Microbial biomass P; P-Olsen; P-Bray-1; Ferralsol; Saline-sodic soil; Basaltic soils; sodium Hydrogencarbonates; resins; soil parent materials; Available nutrient; clay; land use; basalts; Geogenic factor; pH; soils; organic carbon; land cover; clastic rocks; fractionation; Extraction agent; Ferralsols; basicity; fertilization; volcanic rocks; igneous rocks; Saline sodic soil; Microbial biomass; sedimentary rocks; management; hydrochloric acid
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2011.12.022

The first aim of the present study was to investigate the relationship between microbial biomass P and P fractions, especially the organic P (Po) fractions, in a group of 21 German soils that were relatively low in P availability to plants due to their geogenic origin, clay quality, pH, or level of fertilisation. These German soils were compared with an alkaline saline-sodic soil from Pakistan and a relict Ferralsol. The second aim was to reassess Olsen and Bray-1 extractants for determining microbial biomass P by the fumigation extraction method. The strong positive relationships with resin and 0.5M NaHCO3 extractable inorganic P (Pi) suggest that 1M HCl–Pi is a major source of these two labile P fractions. The fraction NaHCO3–Po was the smallest Po fraction, but that with the most specific features. It significantly increased with increasing soil organic C content in the order arable<grassland<forest soils and was also closely related to the soil microbial biomass. The high percentage of NaOH–Po is a characteristic feature of the three basaltic soils, ranging from 19 to 41% of total P. Microbial biomass P-Olsen and P-Bray-1 showed a highly significant linear relationship (r=0.98, P<0.001, n=23) and did not differ between the two extractants. P-Bray-1 has a slightly lower CV and thus advantages in soils low in microbial biomass P such as saline-sodic soils, but also in P fixing soils such as Ferralsols and basaltic soils. ► NaHCO3–organic P (Po) was most closely related to microbial biomass P. ► 1M HCl inorganic P (Pi) dominated the saline-sodic soil. ► NaOH–Pi and 6M HCl-Pi characterised the Ferralsol. ► NaOH–Po characterised the basaltic forest soils. ► Microbial biomass P can be accurately determined by Olsen and Bray-1 extractions.