1. Determining the Suitability of Soils for Drainage
Dr. Larry Cihacek
Soil and Range Science Department
NDSU School of Natural Resource Sciences
Fargo, ND

2. Saline soil (photo by Jay Goos)
Sodic soil (photo by NRCS)

3. Salinity/Sodicity Criteria

4. Drainage Benefits Subsurface soil drainage: Reduces salinity
Lowers water table
Warms soil
Allows for earlier tillage and seeding
Increases soil productivity

5. Problems? While most soils are suitable for drainage, some are not.
Some soils have subsurface properties that may prohibit economical drainage practices.
Some soils may have subsurface properties that may result in drainage failure.

6. Flocculated Soil
(From PNW 601-E)

7. Dispersed Soil
(From PNW 601-E)

8. Cation Relationships
(From PNW 601-E)

9. Divalent vs. Monovalent Cations
High EC
Low EC
(From PNW 601-E)

10. Hydrated Ionic Diameters
Golf ball (K+) vs. Tennis ball (Ca++) Baseball (Mg++) Softball (Na+)

11. Steps to Evaluating Soils for Tile Drainage Suitabiity
Identifying Soil Series – Knowledge of Soil Series.
Evaluating Soil Chemical Characteristics or Drainage Properties
Verification of Soil Properties

12. Identifying Soil Series – Knowledge of Soil Series.

13. Sodic Soils

14. Saline/Poorly Drained Soils

15. Evaluating Soil Chemical Characteristics or Drainage Properties

16. Soil Map

17. Soil Map

18. Critical Characteristics

19. 0 to 12” SAR

20. 0 to 12” SAR

21. 12 to 24” SAR

22. 12 to 24” SAR

23. 24 to 36” SAR

24. 24 to 36” SAR

25. 36 to 48” SAR

26. 36 to 48” SAR

27. Subsurface Drainage Suitability Rating (SDSR)

28. Subsurface Drainage Suitability Rating

30. Subsurface Drainage Suitability Rating

31. Subsurface Drainage Suitability Rating (SDSR)
Soil Drainage Suitability Rating will not provide is a comprehensive site evaluation, determination of wetlands and flooding issues, address social or environmental issues, or soil productivity or design information.
Implemented in Web Soil Survey for North Dakota in late 2011.

32. Accuracy of Web Soil Survey
Accuracy is dependent on population of soil chemical characteristics available for the soils found in in the survey area.
Soil series may have significant inclusions of soils that are of greater or lesser hazard.
Soil survey information should be used for only delineating potential problem areas.

33. Verification of Soil Properties

34. Suitability Criteria

35. Actions
If SAR is <6 or SDSR is <0.15 no further action is needed.
If SAR is >6 but <10 or SDSR is to 0.80, verify soil properties by soil sampling.
If SAR is >10 or SDAR is >0.80, DO NOT DRAIN – Permanent cover?

36. Soil Sampling In areas to be sampled:
Sample 3 to 8 points (depending on area size and soil variability) - minimum of 1 sample per 5 acres.
Sample each point separately.
Sample in 1-foot increments.
Analyze soil for pH, EC, cation composition.
Estimate sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP)
Consult with a soil scientist to evaluate hazard.

37. Other Considerations
Hydric soils and hydric soil regulation compliance.
Potential for developing an interpretation index for “Tile Drains and Underground Outlets” (dropped from national Soil Survey Manual in late 1990’s).
0 to 1 rating scale.

38. References
Springer, A. G Water-dispersible clay and saturated hydraulic conductivity in relation to sodicity, salinity and soil texture. M. S. Thesis. North Dakota State Univ., Fargo, ND.

39. Acknowledgements
Illustrations (Horneck, D. A., J. W. Ellsworth, B. G. Hopkins, D. M. Sullivan, and R. G. Stevens Managing salt affected soils for crop production. Pacific Northwest Extension Publ. No. PNW 601-E. Oregon State Univ., Univ. of Idaho, Washington State Univ.
State NRCS Staff.
NDSU Soil and Range Science and Ag and Biosystems Engineering Faculty and Extension Personnel

40. Questions?