Transcript What is a Soil? - University of Tennessee system

Soil and soil-water
relationships
W. Anderson
Murfreesboro Master
Gardener
Feb 20, 2009
From UTK Extension Publications
Planning the Vegetable Garden SP291-M
Soil Preparation for Vegetable Gardens
SP 291-C
Care of the Vegetable Garden SP 291-D
Organic Vegetable Gardening PB 1391
Definitions
• Natural medium composed of solids,
liquids, and gases that occurs on land
surfaces
• Supports plant and animal life
• Upper limit, lower limit, plant roots
• Does not cover all the Earth land surface
• It is not tracked in on the house carpet
Soil Components
• General rule, a soil is about one-half solids
and one-half pores
• Water and air fills the pore space
• Soil air is lower in O2 and higher in CO2
than surface air
– Plant roots
– Biological organisms
Soil Components
• Solids
– Soil texture, relative proportion sands, silts, clays
sized materials, separates
• Sand
• Silts
• Clays
2.0 mm to .05 mm
.05 mm to .002 mm
less than .002 mm
– Clay soils, large surface area; small pores
– Sandy soils, small surface area, large pores
– Clay and Sand differ in ability to provide plants with
water, nutrients, aeration and physical support
– Sands are drier, less fertile but better aerated & able
to support plants
Soil Texture
• Twelve textural classes
• 3 clay textures, 3 clay loam textures, 3 loam
textures
• 0 to 100 % sand, silt and clay by weight
• Example: Clays, > 35% clay sized particles
• Textural class
Possible percentage
– Clay
– Clay loam
– Loam
20% sand, 20% silt, 60% clay
30% sand, 35% silt, 35% clay
40% sand, 40% silt, 20% clay
Soil Components
• Solids
– Aggregate glue sand, silt and clay sized
particles together
• Granular – glue organic matter and calcium
• Destroy soil aggregates – adding sodium
– Density- mass per volume-pore space
– Texture
lbs/cu ft
% pore space
• Loam
84
• Clay loam 79
• Clay
74
49
53
56
http://soils.usda.gov/education/reso
urces/k_12/lessons/texture/
Soil Water Classification for Water
Management
Think of a soil as a sponge lift the saturated
sponge up does water drip.
• Saturation
– Gravitational water - drainable
• Field Capacity [FC]
– Maximum Plant available water
• Permanent wilting point [WP]
– Plant unavailable water
• Air dry
– Unavailable water
• Oven dry
Volumetric Soil Water Content
Ranges
Textural class Θv @ FC
Θv @ WP
Sand
.07-.17
.02-.07
Loam
.20-.30
.07-.17
Silt loam
.22-.36
.09-.21
Clay
.32-.40
.20-.24
Available Water = Θv @ FC - Θv @ WP
Θv * inches of soil = inches of water in soil
http://www.mt.nrcs.usda.gov/technical/ecs/agrono
my/soilmoisture/clay.html
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Clay, Clay Loam, and Silty Clay Loam Soils
Appearance of Clay, Clay Loam, and Silty Clay Loam Soils at Various
Soil Moisture Conditions
75 to 100 percent available 0.6 to 0.0 inches per foot depleted
Wet, forms a ball, uneven medium to heavy soil/water coating on
fingers, ribbons easily between thumb and forefinger.
Irrigation
• Maximize production, vegetable require 1 to 2 ½
inches of water per week
• 1 inch of water over 100 square feet = 8.3 cubic
feet or 520 lbs water
• Less water early in growing season
• More when plants are larger and setting fruit
• Apply water slowly
• Don’t do frequent shallow watering. Why?
Shallow root growth you want deep roots
Irrigation (2)
• Irrigate early to reduce incident and
spread of disease
• Cultivate prior to overhead irrigation to
increase water infiltration
• Trickle irrigation, reduce water use by up
to 50 times
– Reduces weed growth, weed problems, soil
compaction
– Expensive
Irrigation (3)
• Irrigation system
– Back flow preventer must be connected to
water source
– Screen or disk filter
– 10 to 12 psi pressure regulator
– Trickle tape
– Pressure gauge
Irrigation (4)
• Soaker hose – non engineered
– Cheap
– Not uniform water distribution
• Trickle system can be purchased at
garden centers for $100 to $200
Time Irrigation Properly
• Water late in day – increase diseases
• Trickle, drip, furrow – conserve water,
avoid foliage diseases
• Sprinkler irrigation – best done early
morning – apply 1 to 1 ½ inches of water –
wait several days before repeating
• Less frequent irrigation – less foliage and
root diseases
Use Mulches
• Reduce some pest pressures but increase
others
• Reduce moisture stress
• Reduce weed pressure
Maintaining or Increasing Soil
Organic Matter
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Improves structure
Holds water
Increase microbe activity
Stored and releases nutrients
Plants and animals (organic matter) decay
to more stable organic matter called
humus
• Balance between lost and added
Maintaining or Increasing Soil
Organic Matter (2)
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Sandy soils – less Soil organic matter
Clayey soils – more soil organic matter
More soil mixing – less soil organic matter
Tennessee – warm moist climate – favors
decomposition
Using Crop Residues
• Residue source of organic matter
• Left or composted
• If left – may increase insect, disease and
weed problems
• Turning under – breaks down faster –
releases some nutrients
• Fewer insect, disease and weed seed
survive
Using Lime and Organic Fertilizers
• Increase Soil pH
– Ground limestone
– How much? Soil test
– Calcite, dolomite
– Basic slag
– Wood ashes – don’t dump in one spot
Adding Nutrients - Manure
• Manure
– N, P, K
– Poultry manure highest in N, P, and K
– Spread on garden before planting
• 250-500 lbs large animal manure per 1000 square
feet
• 100 to 200 lbs poultry manure per 1000 square
feet
– Irish potato and sweet potato develop scab
and canker if manure is used
Adding Nutrients – non-manure
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Fertilizer
Blood meal
Bone meal
Granite dust
Greensand
Wood ashes
Guano
%N %P2O5
%K2O
8-15
0-3
--2-4
12-28
------3.5
--1-1.5
5-6
--1-2
3-7
.5-12
4-8
1-3
Questions
• What is soil?
• Why manage water? How can a soils field
capacity be used to manage irrigation?
• Why should fertilizer be used? Can
fertilizer improve a plants water use
efficiency?
Water
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Precious resource
Lost water means lost dollars
What is water use efficiency?
Defined as equal to units of crop
production from each available unit of
water
• Example: bushels of grain per inch of
water
• A long term fertility experiment has been
conduct in Illinois. The experiment is
called the Morrow Plots. The plots are on
the National Historic Registry.
The Morrow Plots to gauge WUE
• Plots received only lime, manure, rock
phosphate or bone meal from 1904 to
1955
• 1955 a portion of some plot received lime,
and commercial fertilizer annually
• Fertilized continuous corn used
precipitation more efficiently
• Better management and improved
varieties have also increased crop yield
The Morrow Plots can gauge WUE
• Yields of both fertilized and unfertilized
corn are increasing.
from 1955-1984
Fertilized
Not Fertilized
130-150 bu/acre
40-50 bu/acre
The Morrow Plots can gauge WUE
• Dry weather and poor fertility can reduce
WUE. Proper fertilization that builds high
fertility can help the crop overcome
drought stress.
from 1955-1984
Fertilized
Not Fertilized
3.3 bu/inch of water
1bu/inch if water
Question
• If plants are fed the proper amounts of N,
P2O5 & K2O will these plants:
– Produce more dry matter/acre: T or
F
– Remove more CO2 from atmosphere: T or
F
– Will decrease the amount of water percolation
through the soil and regolith:
T
or
F
– Will increase the amount of chemicals percolation
through the soil and regolith to the ground water:T
or
F
– Will utilize water less efficiently:
T
or
F
What a soil need to grow: 150 bu/ac of corn
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Ingredient
Water
Oxygen
Carbon
N
P
K
Ca
S
Mg
Fe
Mn
B
Cu
Mo
pounds per acre
6 to 8 million
10,200
7800 C or
28,500 CO2
310
52
205
58
33
50
3
.45
.10
trace
trace
supplied
30 to 36 inches of rain
carbon in 6 tons of coal
675 lbs urea
115 lbs TSP
340 lbs KCl
150 lbs ground limestone
Question
• Cost to remove 28,000 CO2/ac from
atmosphere? {basis: cost of Nitrogen}
• 675 lb Urea * 45 lb N/100 lb Urea =304lb N
• 28,000 lb CO2/304 lb N =93 lb CO2/ 1 lb N
• 93 lb CO2 /lb N * lb N/ $ 0.30 =310 lb CO2 / $1.00 of N
• Typical topsoil – approximate composition
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Soil
basis
Solids
% by vol 50
Inorganic
% by vol 40
% by wt
95
liquids Gases
25
25
Organic
10
5
• INORGANIC Fraction
ORGANIC
Fraction
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(decomposed things)
• Sand
Silt Clay
Humus
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• Primary
Secondary
Colloids
• Minerals
Minerals
• Quartz
layer silicate
• Feldspar
hydrous oxide
• mica
Questions
• What are primary minerals?
• What are secondary minerals?
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Soil - Root System
Rye plant in 1 cu ft of soil for 4 months
Length –miles
surface area – sq ft
Roots
385
2550
Root hairs 6600
4320
Questions
• Soil resources in the USA (TN) do not have
enough available nonmetals and metals
elements for normal growth and development of
plants and animals.
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TN land area -1980
Cropland
5.1 million ac
Grassland
5.5 million ac
Woodland
11.7 million ac
Urban
1.7 million ac
Other
1 million ac
Federal
1.2 million ac
Now 14 million ac
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Non-metal elements
N
Se
P
human function
protein
antioxidant
bones & teeth
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Metal
Cobalt
Zn
Mn
human function
vitamin B12
sexual maturity
bone formation, Insulin
Production
red blood cell formation
• Cu
Questions
• Emphasize
– There is a difference between plant available
content and total elemental content
– Soil testing; plant available content
Other topics
• Soil Testing, PB 1061 by Dr. H. Savoy
• Liming Acid Soils in Tennessee, PB 1096
by Dr H. Savoy
Additional topics
• Landscape Irrigation by Dr. J Buchanan, CD in
the extension office
• Commercial WEB sites
– RainBird Irrigation at www.rainbird now look under
landscape irrigation
– Toro Irrigation at www.toro.com/sprinklers/index.html
– Hunter Industries at www.hunterindustries.com
• Book Source: Simplified Irrigation Design ISBM
0-471-28622-22