Development of a New Soil Extractant for Simultaneous Phosphorus, Ammonium, and Nitrate Analysis

A new soil extractant (HA) with the ability to extract NH4, NO3, and P from soil was developed and tested against 32 soils, which varied greatly in clay content, organic carbon (C), and soil pH. The extractant (HA) eliminates the need for separate phosphorus (P) extractants for acid and calcareous soils and maintains the extract pH, on average, within one unit of the soil pH. The extractant is composed of organic root exudates, lithium citrate, and two synthetic chelators (DTPA, EDTA). The new soil extractant was tested against Mehlich 3, Olsen, and water for extractable P, and 1M KCl and water-extractable NH4 and NO2/NO3. The pH of the extractant after adding soil, shaking, and filtration was measured for each soil sample (5 extractants 2 reps 32 soils 1⁄4 320 samples) and was shown to be Received 16 May 2005, Accepted 16 September 2005 Address correspondence to R. L. Haney, United States Department of Agriculture, Agricultural Research Service, 808 E. Blackland Road, Temple, Texas 76502, USA. E-mail: [email protected] Communications in Soil Science and Plant Analysis, 37: 1511–1523, 2006 Copyright # Taylor & Francis Group, LLC ISSN 0010-3624 print/1532-2416 online DOI: 10.1080/00103620600709977 1511 D o w n l o a d e d B y : [ U S D A N a t l A g r i c u l t u l L i b ] A t : 2 1 : 5 9 1 2 A u g u s t 2 0 0 9 highly influential on extractable P but has no effect on extractable NH4 or NO2/NO3. HA was highly correlated with soil-extractable inorganic N (NH4, NO2/NO3) from both water (r 1⁄4 0.98) and 1M KCl (r 1⁄4 0.97), as well as being significantly correlated with water (r 1⁄4 0.71), Mehlich 3 (r 1⁄4 0.83), and Olsen (r 1⁄4 0.84) for extractable P.