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This article in SSSAJ

  1. Vol. 46 No. 2, p. 381-386
    Received: July 15, 1981
    Accepted: Sept 25, 1981

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Quality Parameters of Spring Wheat and Forage Crops Related to Topsoil and Subsoil Thickness1

  1. J. F. Power,
  2. R. E. Ries and
  3. F. M. Sandoval2



Numerous factors affect the composition and quality of crops. One of these factors is soil thickness, which can affect quantity of nutrients available, availability of water, and rooting depth. This experiment was conducted in North Dakota to determine the effects of variable thicknesses of topsoil and subsoil over sodic mine spoils on nitrogen (N) and phosphorus (P) concentrations in blue grama and side oats grama (Bouteloua gracilis and Bouteloua curtipendula), crested wheatgrass (Agropyron desertorum), alfalfa (Medicago sativa), and hard red spring wheat (Triticum aestivum). Milling and baking qualities of spring wheat were also evaluated. Total phosphorus concentration in most crops was not consistently affected by subsoil thickness; however, total P in plant material was usually greatest when subsoil was covered with either 20 or 60 cm of topsoil. Mixing subsoil and topsoil in a 3:1 ratio frequently gave plant P concentrations almost as low as for treatments of no topsoil over subsoil. A notable exception was alfalfa.

Plant nitrogen concentration tended to decrease as subsoil thickness increased. Much of this decrease may have resulted from simple dilution, since total plant growth generally increased as total soil thickness increased to 90 to 120 cm. Except for alfalfa, N concentration was greater in all crops produced on 20 to 60 cm of topsoil over subsoil than on plots with no topsoil or subsoil and topsoil mixed.

Generally, milling and baking properties of the wheat grain were closely related to the grain N concentration. Based on several parameters of milling and baking quality, flour from wheat produced on plots with 20 or 60 cm of topsoil generally was superior in milling and baking properties to flour from wheat on plots with no topsoil or with subsoil and topsoil mixed.

In general, presence of topsoil affected crop quality by enhancing nutrient uptake by the plant. On the other hand, increased subsoil thickness often increased rooting depth and water availability, resulting in increased plant growth and, consequently, dilution of nutrient concentrations in the crops produced.

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