1. 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
This is basically what I want to talk about today.
I tend to talk a little fast so if I’m flying by one let Amanda know and I’ll slow it down. That was the Tor that came across Southern Maryland a couple of years ago.
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
NASIS – national soils database and what interpretations to be calculated (this were previously stored and manual determined)
National endeavor working towards a seamless digital soil survey across the United States.
Talk about definitions, where these interpretations are used, and why we’re calculating them.
Sidebar discussions throw in here and there

4. SOILS DATABASE
Been around since early 90’s; MD late 90’s. Have had a couple of versions. Extremely powerful program.

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

6. SOIL PROPERTY DATA ELEMENTS
List of some properties:
Available Water Capacity
Bulk Density
Cation-Exchange Capacity
Electrical Conductivity
Flooding Frequency,
Duration
Rock Fragments
Horizon Depth
Slope
Liquid Limit
Organic Matter
Particle Size
Percent Passing Sieves
Ponding Depth, Duration ,
Frequency
Reaction, Soil (pH).
Saturated Hydraulic Conductivity
You might be familiar with these. All are in various tables and reports in WSS, SDV, and SDM. All of these would have low, RV, and high values.

7. SOIL PROPERTY DATA ELEMENTS
Used to generate:
“Soil Property Interpretations”
Corrosion
Drainage Class
Engineering Classification
Excavation Difficulty Classes
Potential Frost Action
Hydrologic Soil Groups
Soil Erodibility Factors
Soil Slippage Potential
T Factor
Wind Erodibility Group
and Index
I like to call them “SPI”. Underlined will be calculated.
Basically using those soil properties to generate 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.
Orange are what we’re going to talk about today.

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)
Two main reasons why these SPI are being calculated and why the results could be different then before.

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
One of the pretty neat pictures related to K factor and erosivity.
Another reason for cover crops.
Keeping soil surface covered is important, “at all times”.
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
A key point is that soil erodibility is determined under the standard reference condition where management effects have been eliminated by maintaining the unit plots in a continuous tilled, fallow conditions for a number of years.

14. SOIL ERODIBILITY - K General effect of texture
Fine textures: (clays) resistant to detachment because of aggregation
Coarse textures: (sands) easily detached, but low 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]
Hence the letter f and w.

16. Kf - Based on Wischmeier Nomograph
Pronounced wish meyer. Developed in late 1960’s.
From soil properties.
Show how with highlighter.
Has a mathematical equation that runs the NASIS calculation.

17. Kf and Kw Factor Classes
Tons per acre per U.S. erosivity unit
0.02
0.05
0.10
0.15
0.17
0.20
0.24
0.28
0.32
0.37
0.43
0.49
0.55
0.64
Standard classes used.
To be calculated for each component horizon or layer, major and minor.
Lower number less erosive.
Higher number more erosive.

18. Kf and Kw Factor Classes
Generalizations
Fine textures: (clays)
Coarse textures: (sands)
Medium textures: (loams)
Silts:
Values shown are typical K factors for those texture groups.

19. Kf value classes of less than 2 mm soil fraction
Convert Kf to Kw
Fragment vol. %
Mulch factor 1/
Kf value classes of less than 2 mm soil fraction
.10
.15
.20
.24
.28
.32
.37
.43
.49
.55
.64 5
.90
.09
.14
.18
.22
.25
.29
.33
.39
.44
.50
.58 10
.77
.08
.12
.38
.42 15
.68
.07
.16
.19 20
.61
.06
.17
.23
.26
.30 25
.54
.05
.11
.13
.35 30
.48
.21
.31 35
.04 18 40 45
.34
.03 50 55 60
.02 65 70 75
.01 80 85 90 95
100
Table for conversion RF and Mulch.
Kw always lower then Kf.

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
AGRICULTURAL LAND PRESERVATION
Stormwater Management Plans
NONTIDAL WETLANDS
CRITICAL AREA
2011 MD Stand. And Specs. Soil Erosion and Sediment Control– Design and Construction Manual
Regulations

22. COMAR HES Soils with a slope >15 % or
Soils with a K value >0.35 and with slopes >5 %
Kf or Kw, not sure??
Some Forest regs use just slopes, some use >25% slopes
Critical Area stated USLE
Stand and Spec for Soil Ero and Sed Control stated use Kw
This is why f and w should always be used with K.

23. PICTURES SPEAK LOUDER THAN WORDS Throw in a couple of pictures.
Water and wind
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.
Just a brief review of RUSLE2 as related to K factor.

25. NRCS RUSLE2 Select County and Map Unit Component
Kf loaded into equation in “background”
Can’t be changed?
MD RUSLE2 Guide book states it can be changed.
If you don’t have a soil with K, which 99% of ours do.

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
Why RUSLE2 uses Kf.

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
erodibility factor.

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
NASIS database has a element entry for surface rock fragments but hasn’t been populated in all components. Plus data not available outside NASIS.
OM similar to rock cover. Inherit OM is in Kf nomograph. OM on surface is a cover & management factor.

30. Guidelines for Rock Cover in RUSLE2
Or use table from MD RUSLE2 User's Guide /2008
Surface texture modifier found in component name.
RUSLE2 Rock Fragments Defined as > 3/8 in size

31. Where to find Kf?
Web Soil Survey, Soil Data Viewer, Soil Data Mart, or eFOTG

32. General trends for results of K 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
This data based on Major components only.
Doing draft calculations:

33. General trends for results of K Calculations in Maryland
Western Coastal Plain and
Upper Eastern Shore Soils
K for ~ 20% components will increase by 1 or more classes
~ 39% are C and D slope map units
K for ~ 48% components will decrease by 1 or classes
~ 37% are C and D slope map units
This data based on Major components only.

34. General trends for results of K 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
This data based on Major components only.
B slopes could be important also since they range up to 8%.

35. General trends for results of K 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
This data based on Major components only.
B slopes could be important also since they range up to 8%.
Looks like pretty much across the state will be evenly affected by the calculation of K.
Both increase and decrease of the K classes.

36. Half Way Through Questions so far?

37. Factors of Soil Formation: s = f' ( cl, o, r, p, t )
One of the most important things to understand about soils.

38. Three Areas of Importance
HEL DETERMINATIONS
Three Areas of Importance
When to use Frozen 1990 HEL Map unit list
Field visit for PHEL areas or where SS updated since 1990
CRP – Different HEL Determinations
This can be confusing.
I had to read it several times in NFSAM Sec. 511.
We don’t do it very often anymore, I think.

39. HEL Frozen Map Unit List - 1990
Used for HEL or NHEL
PHEL - onsite required for determination
to verify HEL or NHEL
Most of these determinations should have been completed in the past.

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)
May not have been done in past.

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
No map unit on Frozen List will have its HEL determination changed.

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
Procedure has changed several times since 1990.
Uses average of 3 major soils in acreage, being offered into CRP.
Cannot be compared to HELC/WC (AD 1026) compliance determination.
Two different technologies and procedures.

43. Maryland COMAR HES Highly Erodible Soils
NRCS/FSA HEL DETERMINATIONS
Highly Erodible Land
HEL Frozen Map Unit List
Maryland COMAR HES Highly Erodible Soils
Soils with a slope >15 % or
Soils with a K value >0.35 and with slopes >5 %
Just to review of the two. Different! Highly Erodible Land vs Highly Erodible Soils.

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
Tons per acre. Measured by USLE and RUSLE2.
Obviously class 5 (tons allowable loss) is better than 1 (ton allowable loss)
To be calculated for each map unit component, major and minor.

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.
Based on soil not frozen.
Based on soil surface bare.
Slope is not considered.

47. T Factor - Soil Loss Tolerance
19 Soil Characteristic in Criteria:
Organic
Bedrock
Fragmental
Rock fragments
Fragipan
Sandy substratum
High aluminum
Important ones in MD and DE.

48. Maryland Soil Property Changes
T Factor Calculations
Maryland Soil Property Changes
Piedmont/Mountain Soils
Bedrock
Fragipan
Rock fragments
Coastal Plain Soils
Sandy substratum
High aluminum (may over ride)
Remember I said there was a change in criteria of the soil properties used to generate the T factor interpretations.
Bedrock & Fragipan: revised to include more taxonomic classification criteria
Rock fragments: removed size criteria
Sandy substratum: removed regional geo-political guides (MLRA’s) in criteria; added more specific Ksat data
Al saturation: brand new soil property criteria considered
Other reasons: some errors in database; some “null values” in database where data is required;

49. Where is T factor used? NRCS RUSLE2 NRCS – Highly Erodible Land (HEL)
NRCS – Many Conservation Programs
State Land Planning Programs
Commonly serves as goals for conservation planning on farms.
Assist in the identification of cropping sequences and BMP’s that maximize production and sustain it.

50. General trends for results of T Calculations in Maryland
Lower Eastern Shore Soils
T for ~4% map unit acreage will increase by 1 or more classes
T for ~20% map unit acreage will decrease by 1or more classes
Based on Major components

51. General trends for results of T Calculations in Maryland
Western Coastal Plain and
Upper Eastern Shore Soils
T for ~17% map unit acreage will increase by 1 or more classes
T for ~35% map unit acreage will decrease by 1or more classes
Based on Major components

52. General trends for results of T Calculations in Maryland
Piedmont Soils
T for ~8% map unit acreage will increase by 1 or more classes
T for ~10% map unit acreage will decrease by 1or more classes
Based on Major components s

53. General trends for results of T Calculations in Maryland
Mountain Soils
T for ~5% map unit acreage will increase by 1 or more classes
T for ~12% map unit acreage will decrease by 1or more classes
Based on Major components
So T calculations will affect the Coastal Plain Soils of Maryland the most.

54. I’m spreading it pretty thick now.
Questions?

55. What are Hydrology Soil Groups??
Definition - group of soils having similar runoff potential under similar storm and cover conditions
Official - National Engineering Handbook, Chapter 7
Classes - A, B, C, and D, and three dual classes, A/D, B/D, and C/D
Just like a soils drainage classes, Class D may be better then Class A or vise verse depending upon the intended use.
To be calculated for each map unit component, major and minor.

56. Hydrology Soil Groups
Criteria - uses soil properties that influence runoff potential
Soil Properties:
Depth to a seasonal high water table
Saturated hydraulic conductivity (Ksat) after prolonged wetting
Depth to a layer with a very slow water transmission rate.
Changes in soil properties caused by land management or climate changes also cause the hydrologic soil group to change.
Like T factors, there was a change in criteria of the soil properties used to generate the HSG interpretations.

57. General HSG Descriptions Based on all when thoroughly wet
Group A Soils - low runoff potential
Group B Soils - moderately low runoff potential
Group C – Soils moderately high runoff potential
Group D – Soils high runoff potential or high water table

58. General HSG Descriptions Based on all when thoroughly wet
Duel Groups – used when D group soils can be adequately drained
Assigned to dual hydrologic soil groups (A/D, B/D, and C/D) based on their saturated hydraulic conductivity and the water table depth when drained.
The first letter applies to the drained condition and the second to the undrained condition.
Example:
Poorly drained Elkton c/d
Poorly drained Hatboro b/d

59. Maryland Soil Property Changes
HSG’s Calculations
Maryland Soil Property Changes
Pre Calculations:
Assignment to group by general criteria guidelines
Example A group: high infiltration rate; deep; well drained to excessively drained sands or gravels
Example C group: slow infiltration rate; moderately fine to fine texture

60. HSG’s Calculations Maryland Soil Property Changes
Present Calculations:
Assignment to group by detailed calculation of very specific criteria
Example A group:
Very specific depths and Ksat (permeability) rates.

61. HSG’s Calculations Maryland Soil Property Changes
Present Calculations:
Example A group:
Every group has three assignment criteria depending upon depth of impermeable layer and or depth to WT.

62. HSG’s Calculations Maryland Soil Property Changes
Present Calculations for Duel Classes:
Example A/D group: WT break is on 24”
Our Drainage class breaks at 20”
Now SWPD have duel classes
Plus our map units with poorly and very poorly drained soils have two major components with drained and undrained phases and they both get assigned duel classes, should be D for undrained and other for drained.
Along with permanently high water table soil.

63. Hydrology Soil Groups Where used?
HSG’s used in equations that estimate runoff from rainfall.
Solving hydrologic problems in planning watershed protection
Flood prevention projects
Planning & designing structures for the use, control, and disposal of water.

64. Hydrology Soil Groups Where used?
Many Federal, State, and Local Engineering Land Use Management programs and practices and BMP’s
RUSLE2 for use in Subsurface Drainage Systems
NRCS Waste Management Soil Interpretations
MDE - SWM and SEC Practices

65. General trends for results of HSG Calculations in Maryland
Coastal Plain Soils
B to other class – 38% of components
Piedmont and Mountain Soils
D to Duel – 11% of components
C to D – 10% of components
C to B – 9% of components
B to A - 8% of components
Big thing on Coastal Plain, the B’s went to A’s.

66. Questions?
x 121