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Thesis (M.S.)—University of Nebraska—Lincoln, 1954. Department of Agronomy.


Copyright 1954, the author. Used by permission.


A mineralogical study was made of some Nebraska soils to determine the amount and significance of potassium feldspar present. The soils included in the study were a catena of soils from the Sandhill region comprised of Dune sand, Valentine, Elsmere, Loup and Gannett and the Tripp soils from the Scotts Bluff Experiment Station. Each Tripp soil was continuously supporting 1 particular field crop for a 40-year period; these crops included potatoes, sugar beets and alfalfa. The soils were studied to determine if these crops had differentially depleted the potassium feldspar content in the fraction greater than 0.02 mm.

The amount of potassium feldspar in the fraction greater than 0.02 mm of all soils was found to be relatively high, and varied from 12 to 26 percent. The reserve potassium feldspar in these soils, therefore, is not in danger of becoming depleted immediately or in the near future.

Considerable variation in potassium feldspar content was shown to exist within the same soil profile and between profiles of the same series.

The largest reserves of potassium feldspar were found in all horizons of the Dune sand and Valentine profiles, the lower horizons of the loup profiles and in the upper horizons of the Tripp soils.

The percent of potassium feldspar represented by cross-sectional area may be more indicative of the long term reserves and may more nearly approach the total amount present than the number count.

The percent of potassium feldspar in the coarse silt fractions was found to be lower than the percent in all fractions.

All surface horizons of the Loup soils showed a wide range in grain size distribution above 0.02mm.

The Tripp soil 1 (the sugar beet crop) was found to contain less reserve potassium feldspar than either the Tripp 2 soil (potato crop) or the Tripp 3 soil (alfalfa crop). The alfalfa crop was higher in reserve potassium feldspar than the Tripp 2 soil.

Advisor: R. P. Matelski.