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DIVISION S-4-SOIL FERTILITY & PLANT NUTRITION

Using an Ion Sink to Extract Microbial Phosphorus from Soil

^a Dep. of Agronomy, Throckmorton Plant Sciences Center, Kansas State Univ., Manhattan, KS 66506-5501, USA

rgm{at}ksu.edu

Two ion sinks (FeO-coated paper and anion exchange resin membrane) were tested to improve accuracy and precision in analysis of microbial P (P_m) in soil biomass. We used a noncarcinogenic biocide, hexanol. Ion-sink extracted FeO-P_m [P_m(FeO)] and resin-P_m [P_m(Res)] were compared with bicarbonate extracted P_m [P_m(Bic)]. Fractional recovery of P_m (K_p) was determined with 50 µg P_m from five different organisms, first, from preparations without soil, giving K_p of 0.49 for P_m(Bic), 0.63 for P_m(FeO), and 0.66 for P_m(Res), and second, from soil-organism mixes, giving K_p of 0.36 for P_m(Bic), 0.49 for P_m(FeO), and 0.52 for P_m(Res). This indicated ion sinks can improve accuracy of P_m recovery. We tested 18 Kansas soils with three different levels of C + N substrates to provide varying levels of microbial activity. For unamended soils, P_m values (mg kg^-1) were 5.9 for P_m(Bic), 8.2 for P_m(FeO), and 6.3 for P_m(Res). Corresponding values in soils with low levels of C + N amendments were 6.0 for P_m(Bic), 18.2 for P_m(FeO), and 18.7 for P_m(Res). In soils with high levels of C + N amendments plus alfalfa (Medicago sativa L.), corresponding values were 12.7 for P_m(Bic), 30.9 for P_m(FeO), and 37.3 for P_m(Res). Above 10.0 mg kg^-1, P_m(FeO) and P_m(Res) were at least twice as much as P_m(Bic). In addition, P_m(FeO) and P_m(Res) both had lower CVs than P_m(Bic), indicating greater precision by the ion-sink methods.

Abbreviations: P_i, inorganic P • P_m, microbial P • P_m(Bic), microbial P extracted with 0.5 M NaHCO₃ • P_m(FeO), microbial P extracted with an FeO-coated paper • P_m(Res), microbial P extracted by strips of anion exchange resin membrane • K_p, fractional recovery of organism P_m • OM, organic matter

This article has been cited by other articles:

				R. G. Myers, A. N. Sharpley, S. J. Thien, and G. M. Pierzynski Ion-Sink Phosphorus Extraction Methods Applied on 24 Soils from the Continental USA Soil Sci. Soc. Am. J., March 1, 2005; 69(2): 511 - 521. [Abstract] [Full Text] [PDF]

				T. H. Dao Ligands and Phytase Hydrolysis of Organic Phosphorus in Soils Amended with Dairy Manure Agron. J., July 1, 2004; 96(4): 1188 - 1195. [Abstract] [Full Text] [PDF]