Using an ion sink to extract microbial phosphorus from soil

Two ion sinks (FeO-coated paper and anion exchange resin membrane) were;tes ted to improve accuracy and precision in analysis of microbial P (P,) in so il 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 wi th 50 mu g P-m from five different organisms? first, from preparations with out 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, recovery. We tested 18 Kansas soils with three diff erent levels of C + N substrates to provide varying levels of microbial act ivity. 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 l ow 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 alfa lfa (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 t he ion-sink methods.