Plant Agriculture: Part 1 Soil Notes

Energy

Plants gather ______ by absorbing sunlight

Matter

Obtained from 2 sources:

• Carbon dioxide (air)

• Water, nitrogen, phosphorus & potassium from soil

List the 5 components of soil

• Hummus - Partially decomposed plants & animal matter

• Rock particles - Contains minerals (iron, potassium, sulfur & phosphates)

• Water

• Air

• Living Organisms

2 ways soil can be formed:

Meachanical weathering - Physical breakdown of rock by wind, water, cold, and heat

Chemical weathering - Molecular nature of rock is changed due to reactions with water, oxygen etc..

What are the soil layers:

O, A, B, C, and R Horizons

O Horizon

Humus. Non-decomposed plant matter

A Horizon

Topsoil. Organic matter mized with weathered rock particles.

B Horizon

Subsoil. Tiny rock particles that leach down from the topsoil

C Horizon

Parent Material. Rock that has undergone little weathering because it is so deep underground

R Horizon

Bedrock. Unweathered, solid rock

What are the 3 particle sizes found in topsoil

Sand - Largest particle size / Lots of space between particles. Water not retained (evaporated quickly & percolated through large spaces)

Silt - Intermediate size, space, and retention

Clay - Smallest particle size, little space between particles. Water is retained because it moves slowly through small spaces

What is the advantage / drawback of Sandy Soil

Bad for farming: heaving leaching of nutrients & soil drying due to rapid percolation rate

What is the advantage / drawback of Loam soil

Ideal for farming. Moderate water retention & percolation rate

What is the advantage / drawback of Clay soil

Bad for farming: becomes waterlogged due to slow percolation rate

What type of ecosystem is present in the Great Plains?

Temperate grassland

How do the Western Plains praires differ from the east? And why

East = taller grass

West = shorter grass

Due to different soil type & rainfall

What is tilling?

Loosens and mixes soil, increasing water percolation and mixing O Horizon humus into the topsoil.

What is erosion?

The movement of soil particles by wind or water

Why was soil in wheat farms so much more vulnerable to erosion?

Native grasses are in the ground all year while wheat is only for 8 months

It also had a much smaller root system

Splash erosion

Raindrops are hitting bare soil. Loosening soil particles. Most severe on sloped land

Sheet erosion

Loss of thin layers of soil as water runs off the surface

Rill/ Gully erosion

Water forms large channels as it carries soil away

What is wind erosion?

Soil being moved by wind

Windbreaks

Rows of trees and shrubs that slow wind as it enters a cultivated area

Switching row crops for cover crops

Must be spaced out, creating areas highly exposed to wind and splash erosion. Completely blanket the soil, sheltering it

Strip Cropping

Alternative row and cover crops, creating sheltering “strips” that keep eroded soil within the farm

Contour plowing

Follows the natural elevation curves of the land. Reduces the speed of water, preventing rill & gully erosion

Terracing

Cuts flat, stair like aras into hill sides, preventing rill & gully erosion

No-Till Agriculture

Seeds w/o turning & mixing up soil. Unplowed soil is not as loose & resists wind & water erosion.