1/24/2011 1 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 2 3 4 • Maricopa County soils: –Mineral –Alkaline –Arid –Probably some caliche –May be rocky and shallow, particularly in foothills –May be saline –May be heavy 5 6
Transcript
1/24/2011
1
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
2
3 4
• Maricopa County soils:–Mineral
–Alkaline
–Arid
–Probably some caliche
–May be rocky and shallow, particularly in foothills
–May be saline
–May be heavy 5 6
1/24/2011
2
7
beachball
frisbee
dime
Soil texture affects water movement
8
Soil Texture Triangle
10
11
Soil Compaction
• Compaction reduces pore space:– Restricts H2O and O2
– Poor root development
12
1/24/2011
3
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
Stomata
• Light, especially blue light
• Water
• Temperature
• CO2
1/24/2011
4
When transpiration > water uptake by roots, wilting occurs.
Water moves down its concentration gradient
• Concentration of water is– Highest in soil
– High in plant
– Low in air
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
1-2-3 Rule
Watering depth1. 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.
1/24/2011
5
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
26
atom
• Cations:– NH4
+, K+, Fe++, Ca++
• Anions:
– NO3-, SO42-
27
Cation Exchange Capacity
Clay particle
Organic matter and clay carry a negative charge
Plant Nutrients
Macronutrients• N
• P• K
• Ca
• Mg
• S
Micronutrients• Fe
• Zn• Mn
• B
• Mo
• Cu28
29
Nitrogen deficiency
30
Phosphorus deficiency
1/24/2011
6
pH is a measure of acidity/alkalinity31 32
33
Zn deficiency
Fe deficiency
• Add nutrients to the soil
• Organic and organic forms
• Usually salts
• Can burn plants
• Must be watered in
34
Fertilizers
Fertilizer analysis
N-P2O5-K2O(nitrogen-phosphate-potash)
Complete fertilizer
Incomplete fertilizer
Slow release fertilizers
35
“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
36
1/24/2011
7
Salinity• Na, Ca, K
and other salts accumulate in soils
37
How does soil become saline?
• Shallow watering
• Fertilizers
• Irrigation water quality
• Application of other salty substances to soil.
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
