Transcript What Makes Soil Good

What Makes Soil Good
 Analysis of soils assists an agricultural
land brokerage professional estimate
the economic potential of the land
3-1
Objectives
 Identify macro and micro nutrients in soil
 Soil texture, structure, and consistence
 Identify horizons in soil profiles
 NCRS capability classification system
 Resources to analyze agricultural property
3-2
Important Concepts for Soils Analysis
 Four major components of soil
 Mineral components develop from parent material
 Organic matter
 Ingredients that make soil solution
 Biological Activity
 Plants draw six macronutrients from soil
3-3
Important Concepts of Soils Analysis (cont.)
 Trace elements or micronutrients
 N-P-K designation for fertilizer
 Soil deficiencies develop from shortages
 Characteristics of soils
 Texture depends on individual particles
 Structure groups soil textures
3-4
Establishing Soil Texture
 Coarse soils - loose and very friable
 Moderately coarse soils - hold together when
moist
 Medium soils - feel velvety
 Moderately fine soils - form clods
 Fine soils - form hard clods
3-5
Soil Structures
 Four distinct structures
 Platy soils - flat plate-like soil
 Prismlike - flat and well defined
 Blocklike - six-sided blocks of aggregate
 Spheroidal - granular and round
3-6
Consistence
 Loose - noncoherent
 Very friable - crush under very gentle pressure
 Friable - crush under gentle pressure
 Firm - crushed with moderate pressure
 Very firm - requires strong pressure
 Extremely firm - resists crushing
3-7
Group Activity 3-1
Group Activity 3-1: Field Testing Soils
The instructor should arrange for an array 5 or 6
different tubs of local soils to be placed in the room.
The class can be divided into groups to inspect the
soils and analyze the soils in terms of texture and
consistency, actually making ribbons etc. They
should discuss and record their answers. The
instructor can then ask the groups for their
findings. Ideally, the instructor could inform the
students of the soil type each sample represents and
give an idea of its capabilities.
3-8
Acidity
 Critical to agricultural activities
 Calcium deficiency contributes
 Measured by pH level
 7 is neutral
 Most crops prosper with 6.5 to 7 pH
3-9
Soil Depth
Depth
Descriptive
Depth
Designation
(inches)
Deep
over 36
Moderately deep
20.01-36
Shallow
10.01-20
Very shallow
under 10
3-10
Slope
Slope
Descriptive
Slope
Speed of
Designation
Percent
Runoff
Nearly level
0-1
slow to very slow
gently sloping
1-3
slow to medium
Moderately
sloping
Strongly sloping
3-5
slow to rapid
5-8
rapid to very rapid
Steep
8-12
rapid to very rapid
Very Steep
12
very rapid
3-11
Erosion
Descriptive
Designation
none to slight
moderate
severe
uncrossable
very severe
Amount of surface
soil removed
< 25 percent
25-75 percent
> 75 percent
> 75 percent
Surface Hazards
no gullies
some small gullies
frequent gullies some
numerous uncrossable gullies
and/or accumulations by wind
3-12
Horizons
 Layers determine the characteristics
 Four major horizons
O
horizons
A
horizons
B
horizons
C
horizons
3-13
Understanding Soil Surveys
 NRCS
 System of eight capability classes
 Suitability of soil for cultivation
 Classes based on limitations
 NRCS system includes several subclasses
 NRCS publishes surveys at the county level
3-14
Soil Classes

Class I - most desirable

Class II - have some limitations

Class III - permanent limitations

Class IV - marginally suited to cultivation

Class V - fewer erosion hazards

Class VI - similar restrictions to class IV

Class VII - similar to limitations of Class VI

Class VIII - cannot be used
3-15
Factors limiting Soil Productivity
Limitations
Moisture holding capacity
Soils type subject to the limitation
all deep and moderately deep coarse and
moderately coarse textured surface soils
with moderately coarse textured subsoil
all shallow and very shallow soils
Soil tillage (workability)
very sticky and plastic fine textured soils
rocky and stony soils
Depth
all soils with less than 36 inches of
available depth
3-16
Factors limiting Soil Productivity (cont..)
Limitations
Slope
Soils type subject to the limitation
all very rapid run-off soils
any soil when run-off rates prohibit
filling the soil's moisture holding capacity
Wind erosion hazard
areas with fewer than 30 inches of annual
rainfall on moderately coarse and coarse
textured surface soils
3-17
Factors limiting Soil Productivity (cont.)
Limitations
Water erosion hazard
Soils type subject to the limitation
all slowly and very slowly permeable
soils with slopes greater than 1 percent
all moderately permeable soils with
slopes greater than 3 percent
all rapidly permeable soils with slopes
greater than 5 percent
3-18
Soil Surveys Contents
 Soil Map
 Description of formation
 Description of soils
 Use and management
 Classification of the soils
 Extensive Glossary
3-19
Soil Surveys
 Assign compound names
 First name indicates soil series
 Second name indicates texture
 Characteristics common to subject area
 Permits identification of soils
 Quality and detail of information varies
3-20
Agricultural Production Capabilities
 Production depends on structure
 Dominant textures
 Topsoil depth
 Rooting depth
 Soil fertility
 Slope characteristics
3-21
Soil Capability Classes

Iowa State University Corn Suitability Ratings CSR
Soil
Area
Index
Type
(acres)
CSR
CSR x acres
_________________________________________________________________
______
Walters loam
23.87
87
2,076.69
Bierschwale clay loam
32.91
-----
59
1,941.69
--------
56.78
4,018.38
Weighted average CSR
4,018.38 / 56.78 = 70.8
_________________________________________________________________
_
3-22
Soil Analysis
 Should draw on various sources
 Indicate the history of the property
 Include local county extension agent information
 May include USDA information
 Information from state level agricultural offices
 Begin with a set of maps
3-23
Topography Examination
 Irrigation
 Methods of assigning water rights
 Impact of water rights on property value
 Drainage - surface or subsurface
 Slopes
 Erosion potential
3-24
Group Discussion
Group Discussion 3-1 Available soils
resources
Introduce several sample soil surveys for the region where the course is
being conducted. Discuss the capability classes and ask students to
identify yields for specific areas on the maps. Discuss the adequacy of
the current surveys.
3-25
Module 3 - Review
 Understand the composition of the ideal soil
and how it supports agricultural production
 Mineral material
 organic matter
 water
 air
 45,25,25,5
3-26
Module 3 - Review
Identify the macro and micro nutrients
available in soils
Nitrogen, Phosphorus, Potassium, Calcium,
Magnesium, and Sulfur
Iron, Manganese, Copper, Zinc, Boron,
Molybdenum, Chlorine, Cobalt
3-27
Module 3 - Review
Understand the concepts of soil texture,
structure, and consistence
Coarse to Fine
Platy, Prismlike, Blocklike, Spherical
Loose to Very Fine
3-28
Module 3 - Review
Identify the horizons occurring in soil
profiles
 O, A, B, and C
3-29
Module 3 - Review
Understand the Natural Resource
Conservation Service (NCRS) capability
classification system
 Eight Productive capacity Classes
3-30
Module 3 - Review
Access resources to facilitate analysis of
the soils of a agricultural property
NCRS soil surveys
Local Sources
3-31
Self-Assessment Questions
 The four major components of soil are
 Soil deficiencies develop because of
 The three main concepts describing soil character are
 The NCRS capability classification system includes all of
the following except for
 Limitations on soils in the NCRS system refer to
 The corn suitability rating (CSR) developed for Iowa soils
3-32