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Abstract
A new soil extractant (H3A-1) with the ability to extract ammonium (NH4) nitrogen (N), nitrate (NO3) N, and phosphorus (P) from soil was originally developed and tested against 32 soils (CitationHaney et al. 2006). H3A-1 is composed of organic acid root exudates, which are naturally occurring, and lithium citrate. In this study, H3A-1 was modified to reduce the extractable iron and aluminum and improve the nutrient extracting relationships with other well-known soil extractants. Correlations show improved relationships with NO3, NH4, PO4, P, potassium, calcium, and zinc when compared to the original H3A-1 as well as standard soil-test methods [Olsen, potassium chloride (KCl), water, Mehlich 3, Bray 1, ammonium acetate (NH4 OAc), and diethylenetriaminepentaacetic acid (DTPA)]. The modifications were tested against the results from the North American Proficiency Testing (NAPT) database, which included 60 soils, varying in pH, organic carbon, and clay content.