Ground Preparation

Good ground preparation will involve a number of physical activities and stages to get the ground ready for the receiving of plants, seeds or turf. Besides the physical activities involved, there is also a number of other factors that must be considered prior to actually starting the preparation work.

Soil type and conditions
Soil type and its conditions are very important considerations when preparing ground and you should ask and find out the following:

1. What is the soil type? Is it clay, loam, silt, sandy, peaty, chalky? The addition of organic matter, sand or horticultural grit can benefit a clay soil by improving drainage and soil structure; organic matter would typically be added to a sandy soil to assist with water and nutrient retention. Topsoil could be added to a silty, peaty or chalky soil to make them more suitable for general plant growth.

2. What is the soil pH? Is it acidic (less than pH 6.0), if so, how strongly acidic is it? Is it alkaline (pH 7.0+), or is it in the slightly acidic range of pH 6.0-7.0, which is suitable for the majority of plants? However, the addition of lime to a very acidic soil may be required.

3. What is the soil structure like? This will affect conditions like compaction, wetness and soil stability. A well-structured soil will typically be one that drains quite well and can be turned over by forking fairly easily as well.

4. Is there a noticeable amount of earthworm activity? You might be able to judge this by looking for surface casts from the earthworms or digging over a small amount of soil and seeing if there are any present. In a good healthy soil, there will be a noticeable amount of earthworms present.

5. If the soil is really hard to fork or dig then it is likely to be compacted, with a relatively high amount of clay content being present and with a poor soil structure. Removal of the soil, installation of drainage works, or other improvements may need to be considered, unless a moist-wet zone is being created for certain plants.

6. Is the site exposed (to wind) or is it sheltered?

7. How much shade is there on the area you want to plant? This will affect the types of plant you can use successfully.

8. Is there a slope? If so, are you going to keep the slope? If you are, you need to think about maintaining the site after it has been planted. If it is a gentle slope then this probably won't cause much of a problem. A steep slope is different; it can be hazardous trying to maintain plants on a steep slope. Can the ground be terraced to make it easier to plant and maintain?

9. Accessibility: What can you physically do with the site? How will it affect the moving of materials? What types of tools and machinery is required?

10. You may also want to consider whether the site you are to 'prepare' has to meet any special requirements; for example:
• Is it to be 'organic gardening only';
• What are the surroundings like and how is it to blend into them?
• Are there any noise restrictions? This might rule out the use of a rotovator.

Weather Conditions
Working on soil when it is wet is not a good idea. The soil is not only difficult to work, being heavier to lift or turn over soil with a fork or spade, but it can also turn into a boggy mess, which is in no-one's interest.

Only work a soil when it is moist to dry. If a soil is too dry, then it will be very difficult to break down into a suitable tilth. This is particularly relevant to a clay-based soil. Too wet or too dry is no good, you have to judge it just right if you are going to prepare this soil type.

If the soil doesn't stick to your work boots then it is usually suitable to work on.

If the weather is hot and sunny then it is important to drink plenty of liquid (not beer or lager though) and ensure your skin is adequately protected against sunburn.

Hazards of underground services
To help reduce the risk from underground hazards try and find appropriate plans of the area that is being worked on, as these should show the general location of any services.

Some of the hazards of underground services might include:
• Electric cable ¯ electrocution.
• Gas pipe ¯ explosion.
• Water pipe - force of water pressure.
• Telecommunications (eg. fibre-optic cables) - damage to communications, including ability to contact emergency services.
• Drainage/Sewage pipes - collapsing trenches and falling into them.

Make an informed opinion of the likely route and location of pipes etc., especially if you can locate the starting and finishing places. For example, there may be a water meter/or stop valve outside of a property whilst the entry of the water pipe into a building is also known by the location of the stop-tap.

The typical route between the two points is usually as direct as possible, so an inference can be made as to the location of the joining pipework. A Cable Avoidance Tool (CAT) detector can be used to locate electric cables.

If any services are present beneath the ground being prepared there it is essential that these are adequately marked out to avoid causing damage from digging.

Careful shallow and gradual hand excavation might be considered so as to disturb the soil surface layer only. Extra care is needed when working in the vicinity of underground services.

Types of land and clearance requirements

Green Field: This is a previously undeveloped area of land and might range from grassland to scrubland. The site might consist mainly of vegetation, such as grass to scrub, including hawthorn and brambles to sapling trees. In addition, the land may also be used for fly-tipping and would therefore contain all sorts of rubbish and debris, from abandoned vehicles, to settees and bed mattresses, to bags of rubbish or brick/plaster waste etc.

Depending upon the site conditions, the method of clearance could be JCB to remove waste; vehicle recovery services (for scrap materials); tractor and trailer; brushwood cutters; strimmers; bill-hooks; scythes or hand saws, such as a bow saw.

Reclaimed Land: This would mostly be on a large scale and might be:
• A land-fill area that is being restored to vegetation.
• Old disused railway line being improved to form a nature trail, as well as for walking, cycling, or a bridle way.
• Reclaiming an old airfield - large concrete runway.
• Quarry converted into a leisure area or nature reserve.

The majority of the equipment for this scale of work would be large: JCB, drots, bulldozers supported by lorries to remove and relocate waste or material.


Urban Derelict / Brown Field: This could be areas like an old housing estate to a single house to disused factories and industrial areas. There will be an increase in the services infrastructure to these areas - electric, gas, water, sewerage, telecommunications. Service providers would need to be informed to ensure supplies have been properly disconnected and to ensure any legal requirements are complied with.

Clearance methods could be similar to reclaimed land, although in small urban derelict areas the use of small excavators (e.g. Bobcats) may be more appropriate in some circumstances.

Existing Sites: These are the sites on which the ground preparation work for this unit would be carried out. Typically, these will be domestic gardens, school or college grounds or local authority parks and amenity areas.

The majority of the equipment will be hand tools, supported by smaller machinery (such as a rotovator), but the use of a tractor and trailer (especially in parks and amenity areas) may also be relevant.

Site clearance for existing sites could typically include the removal or repositioning of:

• Existing shrubs and other plants.
• Fencing removal.
• Furniture (e.g. benches, picnic table).
• Bricks/stones: from paving, planters, retaining walls to raised borders.
• Overgrown vegetation needing to be cleared prior to ground preparation.

A certain quantity of hard debris (cans, bottles etc.) would be expected to be found amongst overgrown vegetation and existing sites.

Levelling
The use of laser levels, measuring staffs and pegs/boning rods would typically be used to aid levelling operations on green field, reclaimed and urban derelict sites.

The type of levelling work undertaken on existing sites, especially smaller ones such as gardens, golf tees, and similar areas would typically be of a minor nature. However, if an existing site had a steep slope which was to be terraced, then this would be a more time consuming and complex levelling task.

Minor levelling works would typically use:
• Wood pegs.
• Spirit level (e.g. 1.8m in length).
• String.
• Measuring tape.

These simple items, if used properly, can be very effective in levelling uneven ground on small areas.

If one area of a site is slightly higher than another then the soil from the higher area would simply be 'cut' and removed and 'filled' onto the lower area. The use of pegs, string and spirit level would identify how much needs to be cut and how much needs to be filled.

If, during the moving around of a topsoil, you find there is less than 150mm remaining from the cut area, then it might be advisable to remove the topsoil first and place it to one side and cut the subsoil to use as the fill in the lower area. Ensure that you have also removed the topsoil from the lower area and placed it to one side beforehand as well otherwise you will end up putting poor quality subsoil on top of usually quite good topsoil.

If this seems too labour intensive and impractical, it might be more cost-effective to purchase some additional topsoil and have it delivered to site; this can then be used to raise up any lower areas of existing top-soil (following it being cut away to fill in depressions) to at least 150mm, although the filled areas will typically have a much greater depth of top-soil if an even surface is being produced.

Soil cultivation
Once a site has been cleared and possibly levelled or evened out, the site, now is the time to cultivate over and improve the soil (if improvement is also required). Cultivation could be digging, ploughing, power harrowing, or similar.

For small areas, turning over the soil by either double digging or single digging offers the opportunity to incorporate and thoroughly mix in a required improvement material. Examples of improvement material can include organic matter, horticultural grit, sand, topsoil, fertiliser, lime or ericaceous compost.

Materials
The types of material that are required can be grouped as follows:
• Fertiliser - Range of types available.
• Organic Matter: Compost (homemade or commercial): Well-rotted or shredded FYM, or similar.
• Lime: For correcting soil acidity.
• Elemental sulphur: for correcting alkaline soils.
• Water supply.
• Suitable Plants, Seed or Turf for the required task.
• Herbicides (selective or contact/residual) for perennial weed control.
• Horticultural Grit.
• Sand.
• Top-soil.

Thoroughly mix in any improvement material so that the amended soil can be more easily worked.

The process of soil improvement will typically be carried out during the final ground preparation stage.

Fertiliser
Adding fertiliser at the cultivation stage can help to:
• Address any nutrient imbalance within a soil.
• Encourage quicker plant establishment.
• Encourage good seed germination and initial seedling development.
• Provide nutrients that can be slowly released for a whole growing season.
• Encourage strong root growth and development.
• Encourage floral development and an abundance of flowers.

Fertilisers can be spread and worked into a soil to ensure nutrient availability is distributed fairly evenly throughout the whole of the cultivated soil profile.

If fertilisers are just applied at the surface then this will encourage roots to exploit the soil in this location - surface roots are prone to drought conditions, which is not a good situation if well-established and deep-rooted plants are a requirement.

Organic Matter
Organic matter is typically added to a soil to:
• Improve the moisture holding capacity of a soil; this is especially useful on a sandy soil which typically drains quite quickly and doesn't retain much water.
• Increase the quantity 'of micro-organisms' within a soil helping to improve soil structure and overall soil quality.
• Provide a slow-release supply of a range of macro- and micro- nutrients.

Light sandy soils will typically require the addition of organic matter and balanced fertilisers. Consider the use of organic and/or controlled release fertilisers in sandy soils because these soils are prone to leaching (i.e. the washing away of nutrients).

Loamy soils may only need a small application of organic matter if they are on the lighter (sandier) side, or sand if slightly on the heavier (clayey) side. Fertiliser - a normal compound fertiliser would suffice - should still be applied.

Clayey soils will typically require a fair amount of improving. This may include the incorporation of the following:
• Lime to help break down thick clods into finer aggregates.
• Organic matter to help create a good soil structure.
• Fertilisers to improve the soil nutrient status: Clay soils can be relatively rich in some nutrients, e.g. phosphorus, potassium, so there may only be a requirement for fertiliser with low nutrient levels.
• Sand might be ameliorated (i.e. well-mixed) into the top 25 to 50mm of the surface layer to help it dry quicker and make it easier to provide a finer surface tilth.
• The use of horticultural grit at the base of planting holes may also be considered to help with localised drainage.

Acidity and Lime
Some compost may be acidic, which is essential for acidic loving (lime hating) plants such as some Heathers, Azaleas, Rhododendron and some other plants. This compost will typically be called 'Ericaceous compost' as it is ideally suited to plants in the Ericaceae family.

If a soil is very acidic, e.g. below pH 6.0 to 5.5 then the application of lime to the soil during ground preparation may be required. This will depend upon the type of plants wanting to be grown in the soil. The majority of plants will establish and develop strongly in soils with a pH of 6.0 to 7.0.

Ensure there is an adequate rootzone depth for the acid loving plants to explore before they encounter the less desirable (from a soil pH perspective) existing soil.

Herbicides
Herbicides are pesticides that can be used to control perennial (or other) weeds. Some deeply rooted perennial weeds can be especially difficult to control, e.g. Horsetail. Whilst cultural control, such as hand weeding, would be the recommended method for many situations, the use of a herbicide at the ground preparation stage can increase the chance of establishing and maintaining an attractive planted area.

There are many types of herbicide available and whilst suppliers and retailers will only sell pesticides that are currently approved for use, it is important for a user to ensure they do not have an old stock of pesticide which is no longer approved for use. These pesticides must be disposed of by using an appropriately licensed contractor and must never be poured down drains as this will contaminate water supplies. It is illegal to use herbicides, or other pesticides, that are no longer approved.

The use of herbicides might also be considered prior to the main soil improvement efforts. It might be that a general clearance takes place prior to soil improvement and because of the presence of some persistent perennial weeds it is advisable to apply a non-selective herbicide to kill them, ideally preventing any root fragments from regenerating.

Tools
Choosing the correct tools for the job will help in reducing worker tiredness and will also make the activity safer and more efficient than labouring with limited and ineffective tools and equipment.

Hand tools will typically be used for the size of areas on most existing sites that are small in size, however, the use of a rotovator can help to cultivate over and mix in compost, sand or grit to the surface layer of an area.

Initial treading and raking
Having cleared and cultivated an area you should now be able to follow an appropriate sequence of tasks which will produce a suitable soil tilth ready for planting of flowers, shrubs or trees, or the laying of turf or the sowing of seeds, but the exact requirements will depend upon the purpose of the work in hand.

However, a typical sequence would start with the gradual firming of the soil by treading and raking. Be careful to consolidate the soil in layers of about 75-100mm depth at a time, as if much greater depths are attempted, then the weight of a person will not adequately firm up the lower parts of the soil.

A loose and inadequately firmed soil will be prone to settling and does not provide as stable a ground for root establishment as compared with a well firmed soil.

One particular problem with an inadequately firmed soil is that a shrub may be planted which is initially at the same level as the surrounding soil. As the soil hasn't been adequately firmed the soil will eventually settle and this will leave the base of the shrub sitting proud above the settled soil; this will be exposed to the weather and will dry out relatively quickly.

If plants are not adequately positioned and soil firmed then they will also be more prone to being dug out by animals, resulting in a greater loss rate than those plants in properly prepared ground.

Adequate treading, firming and raking of a soil is even more important for an area that is to be sown with grass seed. If this task is not carried out properly then a very uneven and bumpy turf area will be produced. Not only will this look a poor quality job but trying to mow the area will be difficult as the mower would literally be bouncing along and will be scalping the higher spots, making the finished product look a mess.

Final treading and raking
The process of treading (to firm the soil) and raking (to maintain evenness, break down soil clods and produce a tilth) can be time consuming, but a successfully planted area or turf sward is reliant on this foundational stage.

The fineness of the tilth will be influenced by what is to be achieved:
• If a rose or shrub border, then this may be a 'coarse' tilth;
• For bedding plants, or a turf situation then this may be a 'medium' tilth,
• Whilst for seeded areas this should be a 'fine' tilth.

The number of times that an area will need to be raked then firmed by treading will vary, but it is unlikely that once or twice would be sufficient to provide a suitably firmed tilth.

The following guide may be helpful:
• Coarse tilth: a minimum of 3 treading and raking activities.
• Medium tilth: a minimum of 4 treading and raking activities.
• Fine tilth: a minimum of 5 treading and raking activities.

Applying a fertiliser to the surface of the soil, followed by light raking in should only be needed if the area is to be used for turfing or oversowing with grass or flower seeds.