Unit 5: Soil Surveys &
Land Use Planning
Chapter 17
Objectives




Knowledge of purposes & uses for soil
surveys
Identify tasks for soil survey & the reports
involved
Methods of soil evaluation & interpretation
Use of electronic databases
Introduction


Soil survey – fact-finding mission, following
by a report on the findings
Description of the characteristics of the soils
in a given area



Classification of the soils
Delineate boundaries of soils on a map
Predictions of behaviors of the soils
Introduction

Contain

Data for many users


Farmers, forecasters agronomists: evaluate potential
production of the soil, management needs to
maximize that potential
Planners, community officials, engineers, developers,
home buyers: evaluate the site for building
construction purposes, strengths, limitations
Conducting a Soil Survey

Before any surveying begins, a plan is made
& information is collected




Conferences
Collect aerial photographs
Satellite images
Initial field reviews
Conducting a Soil Survey

Preparation of a legend


Initial field reviews conducted in soil pits in the
most extensive landforms
Soil-mapping unit: area of soil that is
delineated from adjacent areas on a map

Differences may be:



Slope
Erosion
Soil profile
Soil Survey Reports


Normally surveyed on a county basis
Contents of a Soil Survey






Temp & precipitation
Spring/fall freeze dates
Growing season
Acreage & proportional extent of the soils
Prime farmland
Land capability & yields/ac of crops
Soil Survey Reports








Rangeland productivity
Recreational development potential
Wildlife habitat
Building site development
Sanitary facility needs
Construction materials
Water management
Engineering index
Soil Survey Reports






Physical & chemical properties of the soils
Soil & water features
Chemical analysis
Clay mineralogy
Engineering index data
Soil classification
Soil Survey Reports

Mapping Legends for Soils

Typically named for the most extensive soil series
w/in each unit

Each unit often a natural mixture of 2-5 soil-mapping
units


Called soil associations
Delineations on the maps called phases of series
Soil Survey Reports

Value of Detailed Soil Survey Reports


Most soil properties recorded in a soil survey
change very slowly
Typically semiperminent properties:





Land relief (topography)
Soil texture
Organic matter content
Soil lime content
Geologic origin
Soil Survey Reports








Natural fertility
Soil depth
Tendency to accumulate soluble salts
Soil structure
Soil engineering properties
Climate
Natural vegetation
Adapted crops & their expected productivity
Soil Survey Reports

Reasons why a resurvey may be done:





Some information was not gathered in a previous
survey
New management practices
Changes in crops grown
Yield prediction changes
http://soils.usda.gov
Special Soil Designations

Benchmark Soils




Considered to be of great importance in an area
Occupy a key position in the system of taxonomy
~1000 soils in the U.S. designated as benchmark
soils
Soil scientists hope that data from these soils can
be extrapolated for soils for which less
information is provided
Special Soil Designations

Prime & Unique Farmland

Lacking in many states due to many reasons




Climate extremes
Short growing seasons
Mountainous terrain
Some states contain lots of prime farmland


Ex. Jewell Co., KS – 67% prime farmland, Wayne
Co., IN – 74% prime farmland
Some counties in IA - >90% farmland
Special Soil Designations

Prime farmland soils







Best suited to producing food, feed, forage, fiber, &
oilseed crops
Soil properties that lend themselves to sustained high
yields
Need to be treated & managed using acceptable
farming practices
Adequate moisture
Growing season must be sufficiently long
High yields w/ minimal inputs
Least environmental damage
Land Evaluation


Land-use planning done for: urban areas, rural
areas
Major issues:


Quality of environment
Environmental sustainability of ag production
systems



Pollution of nitrate, phosphate, pesticides
Erosion of land
Declining soil fertility
Land Evaluation




Low-input farming
Exploitation of timber & range resources
Engineering use info
Problems caused by these issues may have
various/multiple facets




Agronomic
Economic
Political
Social
Land Evaluation

LESA system – Land Evaluation and Site
Assessment



Guide the conversion of farmland to urban uses
Attempts to preserve the best farmland
Three procedures:



Land capability classification
Current category of land is documented
Soil rated according to capability
Land Evaluation

Land Capability Classification


Classification & sub classification for all soilmapping units in the U.S.
Class I Soils



Can be used continuously for intensive crop
production w/ good farming practices
No restrictions
Class II Soils


More limitations than Class I land for crop production
2-5% slope is main difference
Land Evaluation

Class III Soils





Severe limitations
Requires more special conservation practices than
Class II to keep it continually productive
Can have shallow soil
Slopes 6-10%
Shallow water tables
Land Evaluation

Class IV





Severe limitations for cropping use
Greater intensity of conservation practices for
cultivated crops that Class III
Recommend permanent crops (e.g. pastures)
Slope 12-18%
Class V




Boulders, wetness, problems impractical to correct
Not necessarily erosion risk
Can’t be cultivated
Use for pasture, range, woodland, wildlife habitat
Land Evaluation

Class VI



Slope 18-30%
Same limitations as Class V soils, except more need
for sustainable management practices
Class VII


Severe limitations
Extreme care to protect the soil


Even using grazing, wildlife, timber
Slope >30%
Land Evaluation

Class VIII

Very severe limitations



Steep slopes, rock lands, swamps, etc.
Can only be used for wildlife, recreation, watersheds,
aesthetic appreciation
Land capability subclasses – soil groups w/in
the 8 classes that explain the reasons for
limitations of intensive crop production


e – erosion hazard
w - wetness
Land Evaluation


s – shallow, droughty, stony, permafrost
c – climate too cold or dry
Land Evaluation

Ratings for Soil Potential



Indicates the relative quality of a soil for a
particular use compared with other soils in a
given area
Developed for planning purposes
Supplement land capability classes, woodland
suitability groups, range sites, soil limitation
ratings
Land Evaluation

Soil Potential Index (SPI) – value assigned from
0-100

Yield/performance - sum of costs of corrective
measures + costs for continuing limitations
Data Interpretation for Soil Uses


Can be rated to have slight, moderate, severe
limitations
Severe


Soil will require major soil reclamation, special
design, high costs, or intensive soil maintenance
to use for the item listed
Very Severe

Great difficulty in the soil’s use, high costs, or
both
Data Interpretation for Soil Uses

Slight & Moderate

May indicate problems w/:





Shallow
Low permeability
Strong acidity
High salt concentration
Various other problems
Data Interpretation for Soil Uses

Any soil may be good for one use, but poor
for another


Permeable, well-drained soil – good for crops,
poor for landfills, lagoons, etc.
Clayey soil w/ good, deep drainage – good for
lagoons, ponds; difficult for cropping, unstable
for roads, etc.
Controlling Land Use


Much disagreement at all levels of
government regarding how much control to
impose on land use, and whether to develop
or preserve natural resources
Land-Use Laws & Customs


Very difficult/controversial to control private
property
People generally agree that some controls are
necessary, just don’t agree on what they should be
Controlling Land Use

<1% of U.S. population are farmers


More prisoners than farmers in U.S.
Land-use regulation began w/ 1926 Standard
State Zoning Enabling Act


Gave gov’t right to zone areas for limited uses as
protection to general public
Zoning Laws – local, regional, national gov’t ability
to guide land development
Controlling Land Use

Easements & Contracts – used by gov’t bodies to
implement land-use planning by mandatory action



May demand easement or contract to purchase to specified
reason (e.g. park)
Easement/contract may be broken by gov’t at any time w/ no
penalty, but not by landowner
Public Purpose – nat’l or state gov’t have authority to
purchase land for nat’l/state forests, parks, hunting
areas, flood control dams
Controlling Land Use


Private Sales or Bequests – land trusts & holding
companies promising to protect the land
Eminent Domain – forced legal sale due to
promotion of the general welfare of the public over
private good

Can force you to sell your land
Controlling Land Use

Recent Trends in Land-Use Controls

1 million ac of prime ag land converted to non-ag
uses each year in the U.S.

This trend has prompted some states to pass laws to
protect prime ag farmland



Limited effectiveness
No way for enforcement
Preferential Tax Assessment – made to fit current
use of land instead of other uses that might be
assessed at higher rates
Controlling Land Use


Buying Development Rights – owner sells
development rights to gov’t, but retains ownership to
use at its current use
Enforced Planning – state requiring local gov’ts to
establish & enforce land-use planning, identify most
productive farmland & housing growth areas
Controlling Land Use

Threatened Farms & Farmers


Priority for U.S. to have stable, wholesome,
inexpensive food supply
All 50 states have laws against urban sprawl,
lawsuits that urban dwellers may bring against
farmers for nuisances (odor, noise, dust)




Called right-to-farm laws
IA Supreme Court struck down this law in 1999
What is your reaction?
What should we do to rectify the situation?
Assignment