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“Updates of K factor, T factor, and Hydrologic Soil Groups in the Maryland Soils Database”

“Updates of K factor, T factor, and Hydrologic Soil Groups in the Maryland Soils Database”. Webinar Thursday Feb. 23, 2012 1:00 -2:00 PM. Presented by James Brewer Resource Soil Scientist - Easton, MD. ANY QUESTIONS!!. Don’t hesitate to ask!. WEB INAR OBJECTIVES.

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“Updates of K factor, T factor, and Hydrologic Soil Groups in the Maryland Soils Database”

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  1. “Updates of K factor, T factor, and Hydrologic Soil Groups in the Maryland Soils Database” Webinar Thursday Feb. 23, 2012 1:00 -2:00 PM Presented by James Brewer Resource Soil Scientist - Easton, MD

  2. ANY QUESTIONS!! Don’t hesitate to ask!

  3. WEBINAR OBJECTIVES NASIS – Stored vs Calculated What, Where, Why K Factors T Factor HSG’s Sidebar Discussion RUSLE2 HEL Clarification

  4. SOILS DATABASE

  5. SOIL PROPERTY DATA ELEMENTS Over 150 individual entries populated Many have Low, RV, and High

  6. SOIL PROPERTY DATA ELEMENTS List of some properties:

  7. SOIL PROPERTY DATA ELEMENTS Used to generate: “Soil Property Interpretations”

  8. NASIS – Stored vs Calculated Interpretations • K Factor – Soil Erodibility • T Factor – Soil Loss Tolerance • HSG - Hydrology Soil Groups • WEG – Wind Erodiblity Group • WEI – Wind Erodibiltiy Index • Steel Corrosion • Concrete Corrosion.

  9. NASIS Calculations – Based On? Better soil property data for most, if not all individual components. Both major and minor. (K factors, Corrosion Potentials) Change in criteria used to generate soil property interpretations (T factors, HSG, WEG, WEI)

  10. WHY CALCULATE???? Need to populate commonly used values (property interpretations) Can’t measure directly but can be consistently derived from other date Over entire database

  11. WHY CALCULATE???? • Increase internal consistency in the database • Within map units, components, horizons • In other words: The same “stuff” will have the same “values”

  12. SPLASH EROSION RAINDROPS FALLING ON EXPOSED SOIL CAN BREAK OFF SOIL PARTICLES TO BE LOST IN RUNOFF WATER

  13. What is K factor?? • Measure of soil erodibility under standard unit plot condition • 72.6 ft long, 9% steep, tilled continuous fallow, up and down hill tillage • Major factors affecting it • Particle sizes, organic matter, structure, permeability and yes rock fragments

  14. SOIL ERODIBILITY - K • General effect of texture • Fine textures: (clays) resistant to detachment because of aggregation • Coarse textures: (sands) easily detached, butlow runoff, large, dense particles not easily transported • Medium textures: (loams) moderately detachable, moderate to high runoff • Silts: easily detached, high runoff, small, easily transported sediment

  15. Two Kinds of K Factors Kf applies only to the fine-earth (less than 2.0 mm) fraction [Kf – free of rock fragments] Kw factor applies to the whole soil, includes rock fragments within the soil layer [Kw – with rock fragments]

  16. Kf - Based on WischmeierNomograph

  17. Kf and Kw Factor Classes Tons per acre per U.S. erosivity unit

  18. Kf and Kw Factor Classes Generalizations • Fine textures: (clays) 0.05-0.15 • Coarse textures: (sands) 0.05-0.20 • Medium textures: (loams) 0.25-0.45 • Silts: 0.45-0.65

  19. Convert Kf to Kw

  20. Where is K factor used? • Maryland’s COMAR - Highly Erodible Soils (HES) • NRCS RUSLE2 • NRCS – Highly Erodible Land (HEL) • MDA – Phosphorus Site Index

  21. COMAR Highly Erodible Soils Found in: • FOREST CONSERVATION - 08.19.03.00. • AGRICULTURAL LAND PRESERVATION - 15.15.07.00. • Stormwater Management Plans - 26.17.02.00. • NONTIDAL WETLANDS -26.23.01.00. • CRITICAL AREA - 27.01.01.00. • 2011 MD Stand. And Specs. Soil Erosion and Sediment Control– Design and Construction Manual

  22. COMARHES • Soils with a slope >15 % or • Soils with a K value >0.35 and with slopes >5 % • Kf or Kw, not sure??

  23. PICTURES SPEAK LOUDER THAN WORDS

  24. NRCS RUSLE2 RUSLE2 uses the Kf (fine-earth, rock free) factor Surface layer Kf from NASIS database via Soil Data Mart via Purdue Univ.

  25. NRCS RUSLE2 Select County and Map Unit Component Kf loaded into equation in “background” Can’t be changed?

  26. From MD RUSLE2 User's Guide 06/2008 • The soil object includes information on soil erodibility, soil texture, hydrologic soil group, and rock cover. • Also, this object includes the soil erodibility to compute a value for the soil erodibility factor if one is not available. Maybe??

  27. Adjusting Rock Cover in RUSLE2

  28. Guidelines for Rock Cover in RUSLE2 • Rock cover on the soil surface affect the Cover & Management factor in RUSLE2 • Rock cover (fragments) does not affect the Soil Erodibility factor used in RUSLE2 • RUSLE2 uses the Kf (rock free) soil erodibilityfactor.

  29. Guidelines for Rock Cover in RUSLE2 • Using Kw would would“double account” of the effect of cropping & management • Don’t use rock cover or rock content values from soil survey data • Measure in field like you do plant litter • If present and not entered in RUSLE2, erosion is over predicted

  30. Guidelines for Rock Cover in RUSLE2 Or use table from MD RUSLE2 User's Guide 06/2008 RUSLE2 Rock Fragments Defined as > 3/8 in size

  31. Where to find Kf?

  32. General trends for results ofK Calculations in Maryland Lower Eastern Shore Soils • K for ~35% components will increase by 1 or more classes • K for ~25% components will decrease by 1 or more classes • This may not have a lot of impact, as there is not much farm land with >5% slope

  33. General trends for results ofK Calculations in Maryland Western Coastal Plainand Upper Eastern Shore Soils • K for ~ 20% components will increase by 1 or more classes • ~ 39% are C and D slope mapunits • K for ~ 48% components will decrease by 1 or classes • ~37% are C and D slope map units

  34. General trends for results ofK Calculations in Maryland Piedmont Soils • K for ~ 35% components will increase by 1 or more classes • ~ 46% are in C and D slope map units • K for ~ 22% components will decrease by 1 or more classes • ~ 37% are in C and D slope map units

  35. General trends for results ofK Calculations in Maryland Mountain Soils • K for ~ 28% components will increase by 1 or more classes • ~ 46% are in C and D slope map units • K for ~ 45% components will decrease by 1 or more classes • ~ 25% are in C and D slope map units

  36. Half WayThroughQuestionsso far?

  37. Factors of Soil Formation: s = f' ( cl, o, r, p, t )

  38. HEL DETERMINATIONS Three Areas of Importance • When to use Frozen 1990 HEL Map unit list • Field visit for PHELareas or where SS updated since 1990 • CRP – Different HEL Determinations

  39. HEL Frozen Map Unit List - 1990 • Used for HEL or NHEL • PHEL - onsite required for determination to verify HEL or NHEL

  40. Field Visit Includes PHEL Map Units • Verify HEL or NHEL to finialize. (maybe due to field boundary changes) • New determination can be issued for specific crop field. (using Jan. 1990 K and T factor data)

  41. Soil Survey Updated Since Jan. 1990 • Any new HEL map units can be appended to the Frozen List • Crop fields with previous HELC determinations will not be changed by any additions of new map units to the list

  42. CRP – HEL Determinations (Automated System) • Doesn’t use Frozen Map Unit List -1990 • Doesn’t use specific soils mapping of original HEL • Uses current soils data in Toolkit (SDM) • Uses average of 3 major soils in acreage

  43. Maryland COMARHESHighly Erodible Soils NRCS/FSA HEL DETERMINATIONS Highly Erodible Land • Soils with a slope >15 % or • Soils with a K value >0.35 and with slopes >5 % • HEL Frozen Map Unit List - 1990

  44. NOT TIME TO RELAX YET! Questions?

  45. What is T Factor?? Soil Loss Tolerance • Definition - maximum amount of erosion at which the quality of a soil as a medium for plant growth can be maintained • Classes - 1, 2, 3, 4, and 5 • T factors - represent the goal for maximum annual soil loss

  46. T Factor - Soil Loss Tolerance Calculated from the soil properties and qualities. Criteria from: 1. The severity of physical or chemical properties of subsurface layers; and 2. The economic feasibility of utilizing management practices to overcome limiting layers or conditions.

  47. T Factor - Soil Loss Tolerance 19 Soil Characteristic in Criteria: • Organic • Bedrock • Fragmental • Rock fragments • Fragipan • Sandy substratum • High aluminum

  48. T Factor Calculations Maryland Soil Property Changes Piedmont/Mountain Soils • Bedrock • Fragipan • Rock fragments Coastal Plain Soils • Sandy substratum • High aluminum (may over ride)

  49. Where is T factor used? • NRCS RUSLE2 • NRCS – Highly Erodible Land (HEL) • NRCS – Many Conservation Programs • State Land Planning Programs

  50. General trends for results ofT Calculations in Maryland Lower Eastern Shore Soils • Tfor ~4% map unit acreage will increase by 1 or more classes • Tfor ~20% map unit acreage will decrease by 1or more classes

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