Transcript Soils - Nmsu

Review
 Symplastic transport
 Apoplastic transport
 In which of the following are
transport proteins are involved?
1.
2.
3.
4.
Facilitated diffusion
Osmosis
Active transport
1&3
 In which of the following are
transport proteins are involved?
1.
2.
3.
4.
Facilitated diffusion
Osmosis
Active transport
1&3
 Which one of the following requires
ATP:
1.
2.
3.
4.
Facilitated diffusion
Osmosis
Active transport
1&3
 Which one of the following requires
ATP:
1.
2.
3.
4.
Facilitated diffusion
Osmosis
Active transport
1&3
 Where is ABA produced?
 Where is ABA produced?
 Roots
 Where is ABA produced?
 Roots
 ABA signals the stomata to open.
 True
 False
 Where is ABA produced?
 Roots
 ABA signals the stomata to open.
 True
 False
Soils
Soil
• How is it made?
• What are some of the physical
characteristics of soil?
• What are some of the chemical
characteristics of soil?
• Are there different types of soil?
– What are they?
Soil

Weathering of rocks




Wind
Rain
Ice
Acid secretion from plant roots
Soil Physics
• Soil Texture:
– Soil is classified by size:
– Sand
0.02 to 2mm
– Silt
0.002 to 0.02mm
– Clay
less than 0.002mm
Soil Properties
Particle Size vs Area
Soil Triangle
Phys
• Bulk Density:
– Weight per unit volume of any soil
• rocks = 2.5 g/cm2
• Soil = 1.5 g/cm2
• Air and water availability

Soil Structure
 Solid
part arrangement
Platy
 Prismatic
 Columnar
 Blocky
 Granular

Soil Horizon

A horizon:
 Smallest
soil particles
 Sand, silt and clay
 Depth
 Humus

Decaying organic
material
 Organisms
Soil Horizon

B horizon:
 Larger
particles
 Less weathered sand
and rocks
 Less organic material
 Depth
Soil Horizon

C horizon:
 Rocky
 Aquifers

Bedrock
Chemical Properties

Cation Exchange Capacity (CEC)


ability of soil to hold positively charged ions e.g.
ammonium (NH4+), calcium Ca++, sodium (Na+)
Function of Texture and Organic Matter


finer texture and O.M. increase CEC
Soils have little ability to hold negatively charged
ions (e.g. nitrate (NO3-))
Chemical Properties

Soil pH



Measure of acidity (hydrogen ions - H+)
Range = 0 – 14
Based on acidity of pure water





Disassociation of water molecule
H20 ↔ H+ + OH10 -7 g H+ and oh- / liter water
-log of 10-7
pH = 7
Chemical Properties
pH
Substance
Soils
2
Vinegar
-
4
Orange juice
Forest
6
Milk
Agricultural soils
7
Pure water
Agricultural soils
8
Sea water
NM soils
9
Soap
Arid
pH vs Plant Nutrients
Cu, Zn
Manganese
Phosphorus
Boron
Iron
4.0
5.0
6.0
7.0
8.0
9.0
10.0
Chemical Properties

Benefits of Organic Matter




Increases CEC (fertility) of soil
Increases water holding capacity
Provides nutrients for plants
Reduces root diseases

How?

Increases the pop. of beneficial microorganisms to out
compete the disease organisms.
Water Holding Capacity

Water Holding Capacity (WHC): amount a water
held by a soil; a function of texture.

Field Capacity (FC): amount of water held against
the force of gravity after irrigation.

Permanent Wilting Point (PWP): amount a water
at which the plant wilts permanently. (Does not hold
well for desert plants)

Available Water (AW): FC - PWP = AW
Conclusions
• Soil texture and depth determine :
– WHC for water storage and CEC for nutrient
status.
– Crop productivity is linked directly to texture
and depth.
• Productivity can be decreased by:
– increased salts
– increased bulk density
Review

Physical Characteristics of Soil

Chemical Characteristics of Soil