Differentiation of four northern Great Plains soils using resin extraction

Resin extraction of soils has revealed sensitivities of crops to the extractable V:(V + P) and Mg:(Mg + Ca) molar ratios. Consequently, we examined the Barnes and Buse soils in the northern Great Plains of North Dakota, South Dakota, and Minnesota. Svea and Langhei soils were included in the survey because of their close association. Samples of A or Ap horizons suspended in 20% ethanol were extracted with cation-(Na+) and anion-(NO) exchange resin-extractors for a period of 5 d. After equilibration, extractors were eluted with 1 N HCl and eluates were analyzed using inductively coupled plasma-atomic emission spectroscopy. Analytical concentrations were log transformed and analyzed using SAS PROC GLM. Each soil produced a distinct suite of extractable ions. Mean pH values ranged from about 6.8 for the Svea soil to about 8.0 for the Langhei soils. Total resin extractable Ca ranged from about 150 to 28 000 nmol g-1 soil and total resin extractable Mg ranged from 110 to 5500 nmol g-1 soil; the least amounts were found in the Svea soil and the greatest amounts were found in the Langhei soil. The pH of the Barnes and Buse soils and the amounts of extractable Ca and Mg in the Barnes and Buse soils were intermediate to those of the Svea and Langhei soils. Trivial amounts of V were detected in extracts from a few samples of Buse soils. Large fractions of S, B, and As in the Langhei soil were extracted on cation exchange resins presumably due to complex formation with the much larger amounts of Ca and Mg. Amounts of Ba, Sr, Fe, Co, Cu, and Si, detected in the extracts differed between soils with more being extracted from the Langhei than from the other soils. Only resin extractable Li and K differed from the general trend in that the amounts associated with Langhei soils were among the least. Detectable amounts of Al, Ni, and Zn usually were obtained but without differences between soils. Resin extractable P was correlated with bicarbonate extractable P but slopes of the regression lines differed between soils and two groups of Barnes soils were clearly distinguished in these relationships. Key words: extractable, nutrients, toxic elements, varadium, sulfur, phosphorus