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This article in SSSAJ

  1. Vol. 48 No. 6, p. 1343-1350
    Received: July 6, 1983
    Accepted: May 10, 1984

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Soil Survey Interpretations from Water Retention Data: II. Assessment of Soil Capability Ratings and Crop Performance Indices1

  1. R. A. McBride and
  2. E. E. Mackintosh2



A water retention model developed for Ontario soils is used to estimate the preseason plant-available moisture-holding capacity (Θva) of the soil root zone in equilibrium with a phreatic surface and the air-filled porosity (ε) of the surface 30 cm. Preliminary soil capability class ratings are then assessed from a set of regional guidelines based on class intervals of Θva and ε. Crop performance indices are determined for capability classes 1 to 5 inclusive using a statistical corn productivity model which relates long-term mean grain corn yields in Ontario to a seasonal soil moisture deficit or surplus. Total seasonal field water supply is budgeted against potential crop evapotranspiration to estimate the extent to which plant water stress from excess or deficit soil water availability limits the attainment of regional agro-climatic potential yields. Advantages in using a water retention model as a basis for agronomic interpretations of soil survey data for land evaluation purposes are discussed.

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