Lecture 18: Soil and Water - 11/13 Flashcards
What are the 5 components of soil?
Organic matter, mineral particles, water, gases, organisms
Composition of soil
1/2 mineral and organic matter
1/2 gases, water, living organisms
How is the mineral content of soil classified?
By diameter
How is soil TEXTURE determined?
By its particle-size distribution
What determines soil STRUCTURE?
How individual soil particles are aggregated
A Horizon
The topsoil; the zone of biological activity, leaching, and mineralization. Extends to ~65 cm
B Horizon
The middle layer, or subsoil; leachate accumulates here and there is moderate weathering. Extends from 65-90 cm
C Horizon
The bottom layer, or substratum; a zone of transition between the subsoil and parent material. Extends from 90 cm to bedrock
Parent rock/bedrock
The source of the soil’s mineral particles
Which horizons do plants root into?
Horizons A and B
O horizon
The layer above the A horizon comprised of organic matter in varying stages of decomposition
E horizon
An area that may develop between horizons A and B when there has been significant leaching, leaving a pale layer mostly composed of silicates
Order of horizons
OAEBC
USDA soil classification system
Order, suborder, great group, subgroup, family, series
Why is soil pH important?
Because it has a significant effect on nutrient availability
Cation-exchange capacity
Soil’s ability to retain and exchange cations
What is the optimal pH range for most soils?
5.5-7.0 pH
How can one determine fertilizer needs?
Through soil and tissue analysis or by observing deficiency symptoms
What determine’s a soil’s water-holding capacity?
Its surface area
What are the 3 types of soil water?
Gravitational water
Capillary water
Hygroscopic water
What is the equation for available water?
AW = FC - PWP
AW: available water
FC: field capacity
PWP: permanent wilting point
What is the most efficient watering method?
Drip irrigation
(hydroponics giving a devious sideye in the corner)
