Some properties of Washington County soils and their relation to soil type and plant growth

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Virginia Agricultural and Mechanical College and Polytechnic Institute


  1. Seventy-five samples of soils were taken in Washington County, Virginia. These samples were taken while the soil survey was in progress. In this group thirty-one different soil types were included. The samples were taken from all parts of the county. Notes were made of the soil type, slope of the land, drainage conditions, erosion, and land utilization. When samples were taken from cultivated fields, the yield of the crop was estimated. When samples were taken from pasture, notes were made of the type and condition of the vegetation.

  2. The following properties were determined and studied in relation to soil type and plant growth: pH, available phosphate, available potash, percent organic matter, percent colloids, base exchange capacity, exchangeable hydrogen and present base saturation. The results of these determinations were used in conjunction with the physical properties, which had been determined by the soil survey, in studying the various relationships.

  3. The laboratory methods of determination were devised by soil investigators. The reliability of these methods was discussed by means of reference to literature.

  4. Soils of the same textural class varied widely in percentage colloids.

  5. Soils that are relatively high in available potash varied widely in base exchange capacity, pH, percent base saturation, and available phosphate.

  6. Soils at like pH values showed no relationship of percent organic matter to percent base saturation.

  7. Soils above pH 6.0 contained 125 pounds per acre or more available potash; they were above 65 percent base saturation and were widely variable in available phosphate and organic matter. Soils at similar pH values showed wide variations in available phosphate.

  8. Within the same textural class, and under similar conditions of land utilization, soils varied widely in percent organic matter.

  9. There was some variation in pH values of residual soils of limestone origin. However, the average values of five samples of each were very close together. The average for Dunmore was 5.4, Hagerstown 5.5, and Clarkesville 5.6.

  10. Available phosphate and potash, as well as pH, were closely related to yield of corn and tobacco.

  11. Available phosphate and closely related to quality of meadow. In soils where available phosphate was above 50 pounds per acre quality of meadow was good. Potash was present in sufficient quantity not to be a limiting factor.

  12. A close relationship was found between some of the soil properties studied. The coefficient of correlation between base exchange capacity and percent organic matter was .7191 ± .0376; between pH and exchangeable hydrogen -.6500 ± .0450; between pH and percent base saturation .9008 ± .0147. This high degree of correlation of pH and percent base saturation, it appears, would hold only for a large number of soils. Within this group, soils at like pH values vary considerably in percent base saturation. There was little relationship between percent colloids and base exchange capacity.

  13. In all cases, in pasture soils, where available phosphate was below nine pounds per acre, pastures were of poor quality. There was a gradual decline in the minimum range of available phosphate and potash in the soils from the good, medium and poor quality pastures. There is also a gradual decline in the average pH values as quality of pasture declines.

  14. Evidence is shown that, within a soil type, the properties of the soil, under varying conditions of soil management vary widely. The soil type name gives no indication of the fertility of the soil at the present time. However, associated with the type name are certain physical properties which determine, largely, the possibilities or limitations of that soil type, or the degree of productivity that the type may be built up to under ideal conditions of soil management.