soil and water kelly young ua cooperative extension
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Soil and Water Kelly 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. Ideal Soil Composition. - PowerPoint PPT PresentationTRANSCRIPT
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 depth1. 1 ft - Flowers, vegetables and other small
annuals2. 2 ft – Shrubs3. 3 ft – Trees
Root volume• V = ½( 4/3 π r3)Π ≈ 3.14r = 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 analysisN-P2O5-K2O
(nitrogen-phosphate-potash)
Complete fertilizerIncomplete fertilizerSlow release fertilizers
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“Organic” versus “Chemical” fertilizers
OrganicManure, compost, fish emulsion, etc.Sometimes recycles wasteMay be resource intensiveCan be bulky, heavyMicronutrientsPathogens, weedsSalt
ChemicalAmmonium nitrate, urea, superphosphate, etc.Can be energy intensive to makeLighter weightSaltMust be purchasedSalt
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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 matter2. Fertilizer3. Organic matter
and fertilizer4. Nothing, only
native soil should be backfilled into the planting hole.
Possible causes of “unthriftiness”
• High soil salinity
• Root diseases• Root parasitic
nematodes