Remaining phosphorus estimate through multiple regression analysis. Pedosphere 16

The remaining phosphorus (Prem), P concentration that remains in solution after shaking soil with 0.01 mol L- ' CaCl2 containing 60 pg mL-l P, is a very useful index for studies related to the chemistry of variable charge soils. Although the P,,, determination is a simple procedure, the possibility of estimating accurate values of this index from easily and/or routinely determined soil properties can be very useful for practical purposes. The present research evaluated the P,,, estimation through multiple regression analysis in which routinely determined soil chemical data, soil clay content and soil pH measured in 1 mol L- ' NaF ( ~ H N ~ F) figured as P,,, predictor variables. The P,,, can be estimated with acceptable accuracy using the above-mentioned approach, and ~ H N ~ F not only substitutes for clay content as a predictor variable but also confers more accuracy to the P,,, estimates. Key Words: anionic adsorption, P H N ~ F, pedotransfer functions, tropical soils The remaining phosphorus (Prem) consists of the P concentration that remains in solution after shaking a soil sample with 0.01 mol L- ' CaC12 containing 60 pg mL-l P. Although Netto and Barbosa (2005) showed that the use of a soi1:solution ratio of 1:50 should be more convenient, the current method used in Brazil for P,,, determination consists of shaking 2.5 g of soil for 1 hour with 25 mL of 0.01 mol L- ' CaC12 containing 60 pg mL-l P, filtering or centrifuging the suspension and analyzing th