New extractant for soil test evaluation of phosphorus, potassium, magnesium, calcium, sodium, manganese and zinc

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Abstract
A new soil test extractant was evaluated which would allow simultaneous extraction of several plant nutrients over a wide range of soil properties and eliminate the present need for grouping of soils. The new extractant is composed of 0.2 N NH4Cl-0.2 N HOAc-0.015 N NH4F-0.012 N HCl at approximately pH 2.5. It was compared to Bray 1 (0.025 N HCl-0.03 N NH4F), Olsen (0.5 M NaHCO3, pH 8.5), DA (0.05 N HCl-0.025 N H2SO4), 0.075 N HCl and DAF (DA [double acid extraction:hydrochloric and sulfuric acid] + 0.008 N NH4F) for extractable P. The uptake of P by millet grown in the greenhouse on 6 taxonomically different Ultisols at 2 rates of lime and 6 levels of P was correlated with the chemically extractable P. In addition, K, Mg, Ca, Na, Mn and Zn extracted by the new method from 122 acid to calcareous soils from the USA and Jamaica were compared to those extracted by DA, while K, Mg, Ca and Na extracted by the new method were also compared to those extracted by neutral, normal ammonium acetate. The ratio of extractable P by 0.075 N HCl/DAF was used to classify soils into groups of < 0.34, 0.34 - 0.66 and > 0.66. P uptake by millet was highly correlated with the P extracted by the new extractant, Bray 1, and DA, followed by Olsen.