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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Livestock Nutrient Management Research » Research » Publications at this Location » Publication #317779

Title: Phosphorus concentrations in sequentially fractionated soil samples as affected by digestion methods

item DO NASCIMENTO, CARLOS - Universidad De Sao Paulo
item PAGILIARI, PAULO - University Of Minnesota
item SCHMIDT, DJALMA - University Of Santa Catarina
item He, Zhongqi
item Waldrip, Heidi

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2015
Publication Date: 11/16/2016
Citation: Do Nascimento, C., Pagiliari, P.H., Schmidt, D., He, Z., Waldrip, H. 2016. Phosphorus concentrations in sequentially fractionated soil samples as affected by digestion methods [abstract]. In: ASA-CSSA-SSSA Annual Meeting. Nutrient Management & Soil & Plant Analysis Poster Session. November 18, 2015, Minneapolis, MN. 420-11.

Interpretive Summary:

Technical Abstract: Sequential fractionation has been used for several decades for improving our understanding on the effects of agricultural practices and management on the lability and bioavailability of phosphorus in soil, manure, and other soil amendments. Nevertheless, there have been no reports on how manipulation of different fractions prior to analyses with inductively coupled plasma optical emission spectroscopy (ICP OES) affects the total phosphorus (TP) concentrations measured. This study investigated effects of sample digestion, filtration, and acidification on the TP concentrations determined by ICP OES in 20 soils collected in Brazil and the United States. Soils were sequentially extracted with water, 0.5M NaHCO3, 0.1M NaOH, and 1.0M HCl. Concentrations of TP in extracts were either determined without digestion by ICP OES, or ICP OES following block digestion or autoclave digestion. The effects of extract filtration and acidification on undigested NaHCO3 and NaOH extracts prior to ICP OES were also evaluated. Results showed that TP concentrations measured in block digested extracts were greater than in autoclave digested and undigested extracts. However, the variability introduced by the block digestion method was much greater than with the other two methods. The effects of filtration were contradictory: in some soil extracts filtration caused a decrease in measured TP and in others there was an increase. Acidification of NaHCO3 extracts resulted in lower measured concentrations of TP, while acidification of NaOH extracts resulted in both increases and decreases in TP. In conclusion, this study showed that ICP-OES of undigested extracts resulted in the lowest variability among the sample preparation methods and should be the preferred method for TP determination in sequentially extracted soil samples.