Soil horizon/profile

Question 1

What is a Soil Horizon/ profile?

Answer 1

An area used to indicate the type of soil in an area

Question 2

How do you obtain a soil horizon?

Answer 2

Dig a pit and measur the soil depths

Question 3

Name the horizons typically found

Answer 3

O-Organic/leaf litter layer
A-Top Soil
B-Sub Soil
C-Parent Rock
Bed Rock

Question 4

Describe the leaf litter layer

Answer 4

Has turf/weeds/plant material on it

Question 5

Describe Top Soil

Answer 5

The part used for crops
A mix of organic matter, gravel, stones, animal and plant waste.
Dark in colour due to presence of humus

Question 6

Describe Sub soil

Answer 6

Lighter in colour as less humus
Nutients from above layer leached down so more clay like structure
Less soil organism life and less plant roots

Question 7

What is Humus?

Answer 7

The black jelly that coats soil particles.
Created by broken down organic matter created by soil organisms and bacteria in soil
Gives top soil it’s dark colour

Question 8

What is weathering?

Answer 8

The break down of rocks by:

Physical-water, wind, heat, frost, glaciers

Chemical: rainfall (carbonic acid)

Biological: action of all organisms-humans and animals and lichens on rocks

Question 9

How does water break down rocks?

Answer 9

Moving water can carry particles in it.
The faster it moves the more it can carry.
Rocks being carried, knock against each other and those on the river bed so are scoured down.

Question 10

How does wind break down rocks?

Answer 10

Sand blasting.

Wind carries abrasive particles and they rub against each other.
typically in hot climates

Question 11

How does frost weather rocks?

Answer 11

In temperate areas.
Water gets into cracks, expands as it freezes, and that pressure forces the rock to crack more
Common in porous rock like chalk and limestone

Question 12

Glaciers weather rocks how?

Answer 12

Ice sticks to adjacent rocks, the debris in the glacier scours against other material as it moves downhill like a scrubbing brush

Question 13

What is biological weathering?

Answer 13

The action of plants and animals including humans on rock.

Eg: patches of lichens on rock
Humans mining

Question 14

List three symptoms that indicate plants are lacking in nutrients

Answer 14

Chlorosis- yellowing of foliage
Stunted growth
Reduced yield/fruiting
Bitter pit in apples that are calcium deficient
Leaves can go purple in tomatoes that lack phosphorus

Question 15

How can the growth of plants be increased without using fertiliser?

Answer 15

Use of organic mulch-reduces water loss and suppresses weeds

Remove weeds-reduces competition for nutrients, light and water

Question 16

How can the growth of plants be increased without the use of fertilisers?

Answer 16

Use of mulch-suppresses weeds and retains moisture

Remove weeds-reduces competition for water, light and nutrients

Adequate water supply

Avoid overcrowding

Suitable temperature to induce growth of plant

Question 17

Name a distinct horticultural situation for the use of the following fertiliser:

Top dressing
Base dressing
Liquid feed
Foliar feed

Answer 17

Top dressing: lawn
Base dressing- tree planting
Liquid feed-tomato’s
Foliar feed- camellias and roses (to overcome lime induced chlorosis)

Question 18

State two effects of pH on soil structure

Answer 18

Soil organisms cannot decompose OM as efficiently so less nutrients put into soil

Also less soil organisms in general

Flocclation necessary so soil more workable

Question 19

Describe the use of one named material to raise pH

Answer 19

Lime lowers acidity.

After digging apply 500g per sq metre

Lime isn’t effective on dry soil so must be watered in

Must be incorporated into soil

Use a lime spreader or spread by hand

Must be crushed or in powder form as not very soluble

Carry out liming prior to a crop being sown/planted

Question 20

What is a benefit of using sulphur?

Answer 20

Easy to apply
Measured accurately 
Fast acting
No impact on soil structure
Can be slow to act depending on particle size and requires re-application

Question 21

What is advantage of adding organic matter

Answer 21

Improves soil structure
Adds micro-organisms to soil
Natural
Sustainable
The ability of om to lower pH of soil is variable and requires re-application

Question 22

Describe how the formation of a soil cap can form in the surface of soil

Answer 22

Falling rain or over watering/cultivation caused soil structure to break down.

Lack of Organic matter contributes

More common in fine soil as particles bond together and form a crust when they dry out

As there is nothing to hold the particles together, they fall into the gaps in the soil surface causing them to block so surface water runs off.

Question 23

List three ways of minimising a soil cap

Answer 23

Water using a rose on watering can -or upturn it.

Avoid working on soil if too dry or rain imminent

Use a layer of Organic matter or mulch to protect surface
Hoe regularly between rows and seedlings

Question 24

State two effects a soil cap can have on plant growth

Answer 24

Seedlings cant penetrate cap

Water runs off surface , roots cant access water so wilting and poor growth occurs

roots unable to access oxygen as pore spaces in soil are filled

Question 25

What is meant by a pore space?

Answer 25

Pores are the spaces between the solid matter of soil

Macropores
mesopores
Micropores

Question 26

What is Available Water Content?

Answer 26

Water available for a plant to uptake and is held on the mesopores

Available water decreases as the volume of air in the soil increases

Question 27

Saturation Point

Answer 27

This is reached when all the pore spaces in the soil are filled with water

Question 28

Permanent Wilting Point

Answer 28

No more water available in soil for plant

macropores and mesopores are filled with air

No water available to plant in root zone

Question 29

Soil moisture deficit

Answer 29

the amount of water required to bring the soil back to field capacity

Question 30

What is parent material?

Answer 30

The base level of a soil horizon

Has been weathered over vast periods of time

All the smaller, broken down pieces are mixed throughout the top and subsoil

Question 31

What are the main soil types?

Answer 31

Loam
Sand
Silt
Clay

These are called soil separates

Question 32

Describe loam

Answer 32

A mixture of sand, silt and clay
Ideal for most crops
Well drained
Aerated with a balance of pore spaces

Question 33

Describe a sandy soil

Answer 33

particles are 0.05-2.0mm in size

85% or more of sand

No more than 10% clay

Heats up quickly

Short of nutrients-needs watering and feeding often “hungry”

Easily worked-dries quickly/good drainage

Large pores

Feels gritty when wet

Adding OM helps to bind particles together

Question 34

Describe a clay soil

Answer 34

40% or more clay
particles less than 0.002mm in size
Holds a lot of water and nutrients
poorly drained
slow to warm up in spring
prone to compaction especiallty when wet
Heavy soil, cloddy lumps
Feels slippy when wet

Question 35

How can a clay soil structure be improved?

Answer 35

frost helps break down the large lumps-frost crumb

weathering helps improve structure

Adding bulky OM opens air spaces and improves drainage

Adding Lime helps decrease acidity and encourages it to form crumbs

Question 36

Describe a silt soil

Answer 36

Micro-sand particles 0.002-0.05mm

Pores are smaller than sand pores

Feels silky/soapy when wet

Reasonable drainage

Holds more moisture than sand-sufficient for plants

Hard to manage as unstable characteristics

Question 37

What is average composition of soil

Answer 37

water: 20%-30%

Air (pore spaces) 20%-30%

Organic matter: 1%-5%

Mineral matter (From parent rock) 40%-60%

Question 38

Define a Macropore

Answer 38

Large pore that holds air

Question 39

Define a mesopore

Answer 39

Medium pore thats holds available water

Question 40

Define a micropore

Answer 40

Small pore, holds unavailable water (Hygroscopic)