Evaluating Soils for Subsurface Drainage Dr Larry Cihacek

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

Quiz � All soils are created equal? T/F ◦ False � All soils are suitable for drainage? T/F ◦ False � Drainage always works in Iowa? T/F ◦ True � Cihacek is opposed to drainage? T/F ◦ False

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++) vs. Baseball (Mg++) vs. Softball (Na+)

Steps to Evaluating Soils for Tile Drainage Suitabiity 1. 2. 3. 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

Critical Characteristics

0 to 12 “ SAR

12 to 24 “ SAR

24 to 36” SAR

Subsurface Drainage Suitability Rating (SDSR)

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.

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 p. H, 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.

Sand Clay Sand Depth E. C. SAR -cm- -m. S/cm - 0 -15 1. 86 5. 97 15 -30 1. 54 8. 82 30 -45 1. 61 10. 2 45 -60 1. 64 11. 4 60 -75 1. 82 13. 9 75 -90 1. 69 14. 1 90 -105 1. 56 14. 7

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?