soil and water kelly young ua cooperative extension
TRANSCRIPT
Soil and WaterKelly Young
UA Cooperative Extension
Objectives:• Discuss soil components, texture,
chemistry• Consider relationships between soil,
water, plants and air• Learn about the properties of water• Compare and contrast fertilizers• Suggest soil amendments
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Ideal Soil Composition
Desert soils have significantly less than 5% organic matter. Why?
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• Maricopa County soils:–Mineral–Alkaline–Arid–Probably some caliche–May be rocky and shallow,
particularly in foothills–May be saline–May be heavy 6
Soil Texture
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beachball
frisbee
dime
Soil texture affects water movement
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Determine your soil texture
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Soil Texture Triangle
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Soil Compaction
• Compaction reduces pore space:– Restricts H2O and O2
– Poor root development
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Capillary Action• Cohesion – “like sticking
to like”– Water molecules stick
together
• Adhesion – “sticking to unlike”– Water molecules stick to
certain surfaces
• Capillary action – drawing of water in a narrow tube
Soil-Plant-Air Continuum
Stomata Factors affecting opening and closing:• Light, especially blue light• Water• Temperature• CO2
Water moves down its concentration gradient
•Concentration of water is–Highest in soil–High in plant–Low in air
When transpiration > water uptake by roots, wilting occurs.
Water loss• Evaporation – change of water phase
from liquid to gas• Transpiration – evaporation of water
from leaves• Evapotranspiration (Et) – combined loss
of water directly from soil evaporation and transpiration
Factors that affect Et
• Temperature• Relative humidity• Wind speed• Light intensity• Type of plant
Terry’s 1-2-3 RuleWatering depth
1. 1 ft - Flowers, vegetables and other small annuals
2. 2 ft – Shrubs
3. 3 ft – Trees
Root volume• V = ½( 4/3 π r3)
Π ≈ 3.14
r = ½ diameter
If a tree has a 12’ diameter:
r = 6’
The root volume would occupy approximately
452 cubic feet.
Root volume
V = ½( 4/3 π r3)Π ≈ 3.14r = ½ diameter
Assume 5 years later the tree has a 20’ canopy:r = 10’Now, the root volume would occupy
approximately 2093 cubic feet!
Soil Chemistry
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atom
• Cations:– NH4
+, K+, Fe++, Ca++
• Anions:
– NO3-, SO42-
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Cation Exchange Capacity
Clay particle
Organic matter and clay carry a negative charge
Plant Nutrients
Macronutrients• C• H• O• N• P
• K• Ca• Mg• S
Micronutrients• Fe• Zn• Mn• B• Mo• Cu 31
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Nitrogen deficiency
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Phosphorus deficiency
pH is a measure of acidity/alkalinity34
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Zn deficiency
Fe deficiency
• Add nutrients to the soil• Organic and inorganic forms• Usually salts• Can burn plants• Must be watered in
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Fertilizers
Fertilizer analysis
N-P2O5-K2O(nitrogen-phosphate-potash)
Complete fertilizer
Incomplete fertilizer
Slow release fertilizers
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“Organic” versus “Chemical” fertilizers
Organic
Manure, compost, fish emulsion, etc.
Sometimes recycles waste
May be resource intensive
Can be bulky, heavy
Micronutrients
Pathogens, weeds
Salt
Chemical
Ammonium nitrate, urea, superphosphate, etc.
Can be energy intensive to make
Lighter weight
Salt
Must be purchased
Salt
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Salinity• Na, Ca, K
and other salts accumulate in soils
How does soil become saline?
• Shallow watering• Fertilizers• Irrigation water quality• Application of other salty
substances to soil.
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Soil Amendments• Used to modify soil chemistry
–Gypsum (Calcium sulfate) – temporarily removes Na from soil
–Soil sulfur – may eventually reduce pH after many yearly applications
–Organic matter
What should be added to the native soil when planting trees and shrubs in the landscape?
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1. Organic matter
2. Fertilizer
3. Organic matter and fertilizer
4. Nothing, only native soil should be backfilled into the planting hole.
Possible causes of “unthriftiness”
• High soil salinity
• Root diseases• Root parasitic
nematodes
