Unit 4:

Land Preparation

PURPOSE OF LAND PREPARATION

The major purposes of land preparation are to:

level the land needed for cultivation.
incorporate crop residues, green manures and cover crops into the soils.
prepare and maintain a good tilth especially in seedbeds.
improve the physical condition of the soil.
help control diseases, weeds, and insects.
help in controlling soil erosion.

STEPS OF LAND PREPARATION

Clearing

This is the removal of original vegetation along with any article that may interfere with land preparation. Some methods of land preparation are:

Manual clearing: using cutlasses, machetes, saws and axes to remove vegetation.
Bulldozing: This is done to clear undergrowth and uproot trees. It is done when the soil is moist and with the utmost care to ensure that debris is not piled up with the surface soil.
Ring Barking: This is an alternative method of removing trees which involves removing a ring of bark roughly 20-45 cm wide from the tree. This causes the tree to die slowly, usually over the course of two years.
Burning

Bulldozing

ring barking

Burning

Burning is a form of land preparation commonly used in the tropics to clear away forested land for farming. Agriculture which utilizes burning to clear the land is referred to as 'slash and burn' agriculture.

Advantages of Burning

An easy method of clearing vast areas of land.
It allows for farming to be done in areas that would otherwise be inaccessible, infertile or infested with pests.
The ash that remains enriches the soil with potassium and nitrogen.
Soils burnt to temperatures less than 400 oC will have increased nutrient availability, increased soil carbon and soil pH (soils become more alkaline) for approximately a year or so.

Disadvantages of Burning

If not carefully controlled, fires can easily get out of control leading to wildfires.
Burning biomass releases carbon dioxide into the air contributing to climate change and air pollution.
Loss of soil organisms
Loss of habitat for wildlife.
Soils will have lower potassium.
Soil nutrients, carbon and pH return to normal levels about 1 year later so the benefit does not last for long.
Soil becomes unplantable after a few years and must be abandoned to fallow.
Recovery of land cleared by slash and burn is slow and it may take between 10 - 25 years and maybe even as long as 40 years before planting can be done again.
When heavy rainfall follows burning severe erosion of the land occurs slowing the return of vegetation.

On the whole, burning is an unsustainable method that is still used in certain parts of the world.

Read the article to the right below and then answer the questions on the form on the left.

Bring Back the Trees on Agricultural Fields!A tree grows tall and deep, spreading both its branches above the ground and its roots underground, therefore it makes the ground fresher…

Land Clearing Quiz

Answer the following questions in your portfolio. You can also fill out the same quiz in the form below if you have the data.

What is land clearing?
Briefly describe two methods of land clearing.
State three reasons why farmers do not plant trees on land. *
What are two reasons why farmers should plant trees on their land?
Give your own definition for agroforestry.
State three ways in which an agro-silvo-cultural system can be implemented.
What four characteristics should a tree used in an agroforestry system possess?

Ploughing

This is the ripping of the soil with a disc, mouldboard or chisel plough. The soil should be ploughed or loosened to a depth of 18-20 cm. Heavy soils should not be ploughed when wet as they become baked when dried, making them more difficult to refine or pulverize.

Ploughing is done to:

bury live vegetation matter so that it can decompose and add nutrients to the soil.
improve oxygen and moisture content of the soil.
produce a good tilth in which seeds can germinate to maturity and yield crops.

Disc Plough

Mouldboard Plough

Chisel Plough

Watch the video on the right.

Listen carefully for the definition of ploughing and no-till and the advantages and disadvantages of both.

Forking

Forking involves the use of the garden fork to till the topsoil. It is an alternative to ploughing and is done in small gardens/farms.

Tilling refers to the breaking up of the soil.

Harrowing

This is the practice of refining or pulverizing ploughed soil. It is usually done a few weeks after ploughing/forking. This is to allow for weathering of the soil. It produces a fine tilth.

Tilling Quiz

Answer the following questions in your portfolio. You can also fill out the same quiz in the form below if you have the data.

What is ploughing?
To what depth is ploughing usually done?
List three reasons why ploughing is done?
What are three disadvantages of ploughing?
What is a no-till system?
What are three advantages of no-till?
What are three advantages of no-till?

Effect of Tilling on the Soil

Watch the video to the right.

Think about the results. Why did tilling cause the soil on the left to come to such a condition?

Drain Construction

Drains are moderate to deep channels made in the soil to get rid of excess water..

They are constructed when the land is flat and subject to waterlogging.

Waterlogging of soils negatively affects plant growth because it:

reduces the amount of oxygen in the soil and so roots cannot respire as they normally would;
causes the death of root tips reducing the uptake of nutrients;
reduces the decomposition of organic matter due to the lack of oxygen, so that plants cannot benefit from it;
increases the amount of carbon dioxide in the soil which affects transpiration and water absorption;
results in the production of methane: a greenhouse gas that contributes to global warming;
causes nitrogen to become unavailable to plant;
causes some metal ions such as iron and manganese to reach toxic levels;
can destroy soil structure in some soils due to the dispersion of clay particles

Drain Construction Activity!

Click here for a practical on constructing drains.

Furrowing

This is the making of beds and ridges. The size of the beds will depend on the crop to be planted and the system of irrigation.

Beds refer to raised flattened portions of ground set aside for planting. Ridges refer to rows of packed, raised soil on which planting can be done.

A diagram of a raised bed.

Possible dimensions for furrows.

A diagram of a furrow.

Possible dimensions for furrows.

Planting may be done on the ridges within areas where rainfall is abundant. Water drains from the ridges into the furrows thereby keeping the crop from becoming waterlogged.

In dry climates, when water is scarce, planting may be done in the furrows where water will accumulate. This keeps the plant irrigated.

A Hugulkultur bed

Hugulkultur

Meaning 'hill culture", hugulkultur refers to an alternative method of preparing beds for farming.

It usually involves:

digging a shallow trench 3 -4 feet wide and a foot deep;
filling it in with wooden logs (freshly cut, long dead or rotten), branches, twigs, wood chips and leaves to form a mound that can be as high as 6 feet or as low as 1 foot;
covering the mound with a layer of soil, usually half a foot to one foot deep;

Land preparation will vary slightly depending on the crop being produced.

Bed Preparation Quiz

Answer the following questions in your portfolio. You can also fill out the same quiz in the form below if you have the data.

What harm does tilling cause to soils?

a. tilled soils do not allow water to drain through

b. tilled soils have greater surface runoff

c. both of the above

d. none of the above

What are drains?

a. Something that deprives you of energy.

b. Moderate to deep channels dug in the soil.

c. The flow of water under the influence of gravity.

d. Shallow holes dug in the soil for planting

Why are drains constructed?

a. To make planting easier

b. To get soil for making a bed

c. To remove water from off of the planting area

d. To accumulate water for plants to use

Drains are only constructed on flat land subjected to waterlogging?

a. True

b. False

Which is not a result of waterlogging?

a. The depletion of oxygen in the soil

b. The production of methane, a greenhouse gas

c. Soil pH becomes acidic.

d. Reduced decomposition of organic matter

Beds are flattened portions of raised grounds while ridges are shallow mounds.

a. True

b. False

Beds are to _____ as ridges are to ____. *

a. drains, furrows

b. furrows, drains

The average depth of a furrow is

a. 10 - 30 cm

b. 15 - 35 cm

c. 20 - 40 cm

d. 25 - 45 cm

Where is planting done when the climate has limited rainfall?

a. On ridges

b. In furrows

What does Hugulkultur mean?

a. The cultivation of crops and livestock

b. The cultivation of crops on small hills or mounds

c. The raising of bees

d. The rearing of fish

Which of the following steps are involved in hugulkultur?

a. digging a shallow trench 3 -4 feet wide and a foot deep;

b. forming a mound with wooden logs and other woody material

c. covering the mound with a layer of soil

d. all of the above

Which of the following steps are involved in hugulkultur?

a. digging a shallow trench 3 -4 feet wide and a foot deep;

b. forming a mound with wooden logs and other woody material

c. covering the mound with a layer of soil

d. all of the above

Sterilization

This is the method of treating the seedbed/box to kill micro-organisms and some insects and weed seeds that are usually damaging to the seeds or seedlings.

Methods of sterilization include:

dusting with chemicals such as insecticides, fungicides and nematicides;
solarization
hot water treatment;
fumigation: allowing poisonous fumes or gases to pass through the soil).

Watch the video to the right or check out the link below to learn about a few methods of sterilizing soil.

https://herbsathome.co/how-to-sterilize-soil/

Then view the table below for some of the advantages and disadvantages of different soil sterilization methods.

Advantages and Disadvantages of Soil Sterilization Techniques

Click here for a practical activity on soil sterilization.

Seedboxes

Seedboxes are portable, miniature containers within which seeds are planted until they germinate.

Seedboxes are preferred for smaller scale farms where fewer seeds need to be planted. They can also save time and effort during the process of hardening off.

Seedboxes are usually:

made of wood, plastic, metal or other natural materials such as eggtrays, eggshells or coconut husks.
possess slots or holes that allow for drainage of water (if made of non-biodegradable material).

Seedbox Plant Media

In the case of seedboxes it is the preparation of the plant medium that is of importance at this point. Plant media used in seedbox preparation are:

coconut coir, tree bark, sand, paddy, soil, organic matter, dry grass/straw.
Perlite/limestone: white granular rock used to loosen up spaces in rooting media and to increase soil pH.
Organic matter

The medium for seedbox has to be prepared in advance before it is placed in the seedbox. Various materials may be used for the preparation of medium for seed boxes.

With the exception of soil, the materials mentioned earlier cannot be used by themselves; rather they must be mixed with other media.

One example of an average mixture for a seedbox:

one part sand
two part soil
three parts organic matter

Seedbox Preparation Activity!

Here is an activity that you can follow to prepare a seedbox for planting.

Seedbed Preparation:

The seedbed is an area of land that has been specially selected and prepared for sowing seeds. Seedbeds should have the following characteristics:

adequately tilled and well-refined soil
Recommended standards for seedbed which will allow the farmers to work from one side of the bed to the center without having to step into the bed when carrying out nursery practice. The length may be extended depending on the crop to be cultivated/planted.
Adequate drainage.
Adequate fertilized soil.
Freedom from weeds, pests and other disease carrying organisms.

A framework is usually constructed around seedbeds to provide shade from the sun, wind and rain until the seedlings are ready to be hardened off, i.e. gradually introduced to the elements.

Seedbed Preparation Activity!

Here are instructions for a practical activity on preparing a seedbed for planting. (Activity needs some further work)...

Soil Sterilization and Seedbed Preparation Quiz

Answer the following questions in your portfolio. You can also fill out the same quiz in the form below if you have the data.

What is soil sterilization? *

a. The process of treating the soil with fungicides, nematicides and insecticides.

b. The process of making the soil barren or unproductive.

c. The process of adding beneficial micro-organisms and macro-organisms to the soil.

d. The process of increasing soil productivity.

Why is soil sterilization done? *

a. To encourage beneficial soil organisms.

b. To produce a starter soil with nothing within it.

c. To remove harmful pests and disease causing organisms.

d. To produce a nutrient rich soil.

Which of the following is not a method of soil sterilization? *

a. Dusting with chemicals.

b. Hot water treatment.

c. Allowing poisonous fumes.

d. Adding beneficial soil fungi.

Which of the following is a disadvantage of soil sterilization by heat? *

a. Simple

b. Ineffective

c. Changes the structure of the soil.

d. No toxic residues.

Which of the following is an advantage of soil sterilization by chemical treatment? *

a. Leaves no toxic residues.

b. Works at low temperature.

c. Changes the structure of the soil.

d. Takes a long time.

Which of the following is not true of using antibiotics to sterilize soil? *

a. Leaves no toxic residues.

b. Simple

c. Ineffective

d. Convenient

A seedbed is an area set aside for the planting of seeds. *

a. True

b. False

Seedbeds are useful for planting seeds on small scale farms while seedboxes are better suited for large scale farms. *

a. True

b. False

Which of the following is not a characteristic of a seedbed? *

a. Adequately fertilized soil.

b. Freedom from weeds, pest and other disease carrying organisms.

c. Adequately tilled soil.

d. Composed primarily of sandy soil.

Which of the following are suitable as a seedbed? *

a. Wooden box with slots in the bottom.

b. Egg tray with holes pierced into the bottom.

c. Old baking pan with holes punched into the bottom.

d. All of the above.

Which of the following materials is used as a growing medium in a seedbox? *

a. Coconut husk

b. Sand

c. Straw

d. All of the above

What is an example of an ideal mixture of sand, soil and organic matter in planting media for seedboxes? *

a. 1:2:3

b. 1:1:1

c. 2:2:2

d. 3:2:1

Discussion

Let's do a review of the lesson...

Post under the appropriate topic in the Forums what you learnt, what you would like to learn and what you do not understand.

Congratulations on having reached this far!

It's time to see what you remember!

Complete the quiz below to see how much you remember from this Unit.

Good luck!

Unit Test

Answer the following questions in your portfolio. You can also fill out the same quiz in the form below if you have the data.

The following are essay type questions. The marks are stated at teh end of each question.

Briefly describe two methods of land clearing. (2)
List three reasons why ploughing is done? (3)
What is a no-till system? (1)
What are three advantages of no-till? (3)
What are three disadvantages of no-till? (3)
Give your own definition for agroforestry. (1)
In what way would planting trees and grass between barriers improve and maintain soil fertility? (1)
Aside from the benefit listed above what are two OTHER reasons why farmers should plant trees on their land? (2)
What four characteristics should a tree used in an agroforestry system possess? (4)

The following are multiple choice questions worth 1 mark each. Choose the correct answer to each question.

Why are drains constructed?

a. To make planting easier

b. To get soil for making a bed

c. To remove water from off of the planting area

d. To accumulate water for plants to use

Where is planting done when the climate has limited rainfall?

a. On ridges

b. In furrows

Which is not a result of waterlogging?

a. The depletion of oxygen in the soil

b. The production of methane, a greenhouse gas

c. Soil pH becomes acidic.

d. reduced decomposition of organic matter

Beds are to _____ as ridges are to ____.

a. drains, furrows

b. furrows, drains

Which of the following steps are involved in hugulkultur?

a. digging a shallow trench 3 -4 feet wide and a foot deep;

b. forming a mound with wooden logs and other woody material

c. covering the mound with a layer of soil

d. all of the above

Why is soil sterilization done?

a. To encourage beneficial soil organisms.

b. To produce a starter soil with nothing within it.

c. To remove harmful pests and disease causing organisms.

d. To produce a nutrient rich soil.

Which of the following is not a method of soil sterilization?

a. Dusting with chemicals.

b. Hot water treatment.

c. Allowing poisonous fumes.

d. Adding beneficial soil fungi.

Which of the following is a disadvantage of soil sterilization by heat?

a. Simple

b. Ineffective

c. Changes the structure of the soil.

d. No toxic residues.

Which of the following is not a characteristic of a seedbed?

a. Adequately fertilized soil.

b. Freedom from weeds, pest and other disease carrying organisms.

c. Adequately tilled soil.

d. Composed primarily of sandy soil.

What is an example of an ideal mixture of sand, soil and organic matter in planting media for seedboxes?

a. 1:2:3

b. 1:1:1

c. 2:2:2

d. 3:2:1

Total: 30 marks

References

SCCP Crops and Soils Curriculum Guide
Image of Bulldozing <https://summersacres.files.wordpress.com/2014/01/55265-bulldozingtheland009.jpg?w=940>
Image of RIng Barking <https://treenet.org/wp-content/uploads/2017/08/ring_barking_1.png>
NSW Government. Impact of Fire on Soil Life and Nutrients <https://www.dpi.nsw.gov.au/content/archive/agriculture-today-stories/ag-today-archives/agriculture_today_february_2006/2006-002/columns/impact_of_fire_on_soil_life_and_nutrients#:~:text=The%20impact%20of%20fires%20on,impact%20of%20fires%20on%20soils.&text=Nutrient%20levels%20and%20soil%20organic,after%20a%20prescribed%20grass%20fire. >
K. Afrane Okese. Slash and Burn: Its Negative Effects on Agriculture and Environment <https://blog.agrihomegh.com/do-not-slash-and-burn/ >
Slash and Burn Agriculture: A Definition, Usefulness, and Disadvantages. <https://www.greenandgrowing.org/slash-and-burn-agriculture/ >
Image of Disc plough <https://www.advance-africa.com/images/StandardDiscPlough.png>
Image of Mouldboard Plough <https://lh3.googleusercontent.com/proxy/hAp8M8kitNVJCCByJrHPglLuezvTdrgkfBvEjetKkHgQNu9Ppfbh8PNinmrOaNdvXyvHWOXFL3K4bQfP84g7qo990PNF1YSjNkdMfcqaqEJUVFZV_IXJj5hSQo2YkQErcA>
Image of Chisel Plough <https://www.researchgate.net/profile/Abd_Al-Kareem_Al-Kheer/publication/278635762/figure/fig13/AS:669429843099670@1536615920954/15-Illustration-of-a-five-shank-chisel-plough-Tine-width-u-rake-angleF-tillage.png>
Image of Furrow <https://www.fao.org/3/s8684e/s8684e0j.gif>
Pavlis, R. Hugelkultur Gardening Method & Hugelkultur Raised Beds. Gardenmyths. <https://www.gardenmyths.com/hugelkultur-gardening-hugelkultur-raised-beds/ >
Image of waterlogged soil <https://www.philpoteducation.com/pluginfile.php/1363/mod_book/chapter/1333/14.2.6b.jpg>
Biological Activity in Waterlogged Soil Image <https://image.slidesharecdn.com/kumarharshr-14018ssc-41104-180901172617/95/waterlogged-soils-22-638.jpg?cb=1535822820>
Soil pH of Waterlogged Soil Image <https://image.slidesharecdn.com/kumarharshr-14018ssc-41104-180901172617/95/waterlogged-soils-14-638.jpg?cb=1535822820>
Department of Primary Industries and Regional Development. Waterlogging: the Science. Western Australia. <https://www.agric.wa.gov.au/waterlogging/waterlogging-science>
Shiffler, A. How to Sterilize Soil? <https://herbsathome.co/how-to-sterilize-soil/ >
Plastic seed tray <https://upload.wikimedia.org/wikipedia/commons/b/b0/Horticulture_Tray3.jpg>
Egg carton seed tray: <https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcSdkO3n9i-NCnvent4rQD2RrZfB0g9VImMPMw&usqp=CAU>
Wooden seed tray image <https://www.wikihow.com/images/thumb/f/ff/Plant-Seeds-in-a-Basic-Seed-Tray-Step-8-Version-2.jpg/550px-nowatermark-Plant-Seeds-in-a-Basic-Seed-Tray-Step-8-Version-2.jpg.webp>

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