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

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

Salinity/Sodicity Criteria

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

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.

Flocculated Soil (From PNW 601-E)

Dispersed Soil (From PNW 601-E)

Cation Relationships (From PNW 601-E)

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

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

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

Identifying Soil Series – Knowledge of Soil Series.

Sodic Soils

Saline/Poorly Drained Soils

Evaluating Soil Chemical Characteristics or Drainage Properties

Soil Map

Soil Map

Critical Characteristics

0 to 12” SAR

0 to 12” SAR

12 to 24” SAR

12 to 24” SAR

24 to 36” SAR

24 to 36” SAR

36 to 48” SAR

36 to 48” SAR

Subsurface Drainage Suitability Rating (SDSR)

Subsurface Drainage Suitability Rating

Subsurface Drainage Suitability Rating

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.

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.

Verification of Soil Properties

Suitability Criteria

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

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.

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.

References Springer, A. G. 1997. Water-dispersible clay and saturated hydraulic conductivity in relation to sodicity, salinity and soil texture. M. S. Thesis. North Dakota State Univ., Fargo, ND.

Acknowledgements Illustrations (Horneck, D. A., J. W. Ellsworth, B. G. Hopkins, D. M. Sullivan, and R. G. Stevens. 2007. 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

Questions?