RHS Level 2 Certificate

Week 17- Outdoor food production. Site selection and cultivation methods

Learning Objectives

1. Selection of site1.1 State the factors to be considered when selecting a site for outdoor food production;

including soil depth, texture and structure, drainage, pH, aspect, slope, susceptibility to frost and wind, area of land available and availability of water.

1.2 Describe the reasons for providing shelter for an outdoor food production area; including the effects of wind reduction, frost potential and influences upon pollination.

1.3 State the benefits and limitations of living and non-living windbreaks. 1.4 Name FOUR plant species suitable for a living windbreak 1.5 Name FOUR types of non-living permeable windbreak. 2. Cultivation techniques2.1 Describe a range of soil cultivation suitable for the vegetable garden: including digging

rotary cultivation, consolidation and tilth production 2.2 Describe how the timing of soil cultivations will be influenced by soil texture, structure,

weather and climate. 2.3 Describe what is meant by the bed system for growing vegetables. Compare this with

open ground production 2.4 Describe what is meant by a raised bed, giving a specification for a typical raised bed

and paths. 2.5 Explain the no-dig system of managing raised beds.

Choosing a site for outdoor food production

Aspect – sunny, south facing. Avoid overhanging trees. Needs shelter from strong prevailing winds. For vegetables avoid sloping sites.

Access – needed for deliveries, moving materials and moving around the site.

Services – water; power. Location of greenhouse if available Soil - pH of 6.5-7 ideally. Suitable depth of top soil and good

drainage. Micro-climate. Avoid frost pockets (cold air gathers in holes

and at the base of slopes). Consider how walls can be used to provide temperature buffering for more tender fruit.

Windbreaks and shelter

Wind can damage plants, it also reduces temperatures and encourages evaporation of water from soil and leaves.

A windbreak can have an effect for a distance of up to 10 times its own height

Windbreaks reduce the risk of plant damage from strong winds. They also encourage pollinating insects, increase local temperatures and reduce transpiration and evaporation. They create a microclimate.

An impermeable windbreak however creates damaging turbulence on its leeward side. For gardens wind permeable wind breaks are better. They reduce wind speed without creating turbulence.

Types of windbreak

Fence Easy to put up, relatively cheap, does not compete with the plants

Solid panels create turbulence; picket or trellis better.

Wall Attractive and permanent.

Heat stores for espaliered fruit trees

Expensive and hard to put up. Usually impermeable.

Hedges Attractive and more permanent than fencing.

Compete with plants for water and nutrients; take time to establish and need maintenance

Windbreak netting Cheap and easy to put up. Easy to move to where it is needed.

Unattractive and not permanent.

Cultivation – to dig or not to dig?

Traditional approach – double digging and regular soil cultivation; digging in organic matter.

No Dig approach – building beds of organic matter and soil on top of the existing site and planting into these.

Advantages of each method

Digging – advantages No dig - advantages

Exposes pests and diseases to the elements and predators

Does not expose annual weed seeds to light – so no need for a ‘stale seed bed’

Incorporates organic material into the soil and allows the elements to break down clods of clay

No need to incorporate the organic matter

Breaks down hard pan and soil compaction

Retains moisture as the raised bed acts like a mulch.

Allows a good depth of root run in well cultivated soil

Encourages worm populations and can be used on most soils

Digging encourages the break down of organic matter by allowing oxygen into the soil.

The use of composted organic material is said to result in fewer diseases and pests

Disadvantages of each method

Digging - disadvantages No Dig - disadvantages

Exposes weed seeds to the light triggering germination

Needs very large amounts of suitable organic material and loam

Labour intensive – very physically demanding

Perhaps less physically demanding but still very hard work to set up

Digging wet soils – particularly clay or loam – can cause compaction

Any hard pan or compaction in the underlying soil is not broken up and this can lead to poor drainage

May damage the soils natural balance – harming animals and good bacteria

Indications are that if used for a long period this method can damage soil fertility.

Double and single digging

Single digging – a trench one spades depth is taken out at the end of the plot and the soil moved to the other end. Then the adjoining soil to the trench is dug and turned into the trench, and so on. At the end the soil from the first trench is put in the last trench. Organic matter is worked in as the soil is dug.

Double digging – as for single digging but the soil at the bottom of the trench being worked (after the top spit has been removed) is forked over to a further spades depth and organic matter is worked in. Sub-soil and top soil are not mixed.

Raking and consolidation

Consolidation – fork over dug soil, rake and then tread to firm. Do not do this on wet clay or silt

Raking is used to create a fine tilth for sowing – good contact for the seeds with moist soil is vital for germination.

Stale seed bed – seed bed is created by raking, any base dressing fertilizer is added, water and leave for 10-14 days to allow weeds to germinate. Hoe or spray off and sow.

Use of the bed system

Traditional vegetable growing is on the row system – long straight lines of the same crop (sown in succession) with spaces between to allow weeding and watering.

The bed system involves the creation of growing beds that are narrow enough to be cultivated without the need to walk on the bed. The bed has paths around it to accommodate walking and wheelbarrows etc.

Advantages of the bed system

Avoids wasting water or fertilizer etc. as this is only applied to the planted area

Allows more dense planting of the growing area

The soil is not walked on so compaction is less of a problem

Crop rotation is easy to plan Beds are easy to protect from cold or from

pests.

Disadvantages of the bed system

Not suitable for larger scale growing (although it is used on a field scale to grow carrots etc)

May lead to development of hard pan and compaction of the sub-soil as double digging is impractical, especially if the bed is raised and framed.

Raised beds

Bed system with a structure (boards, sleepers etc) around it and filled above the level of the surrounding soil.

Very suitable for no-dig systems as new organic matter is contained and only added where needed

Advantages – soil fertility can be high, good where drainage or soil texture is a problem, otherwise as for bed system.

Disadvantages – top up amounts of top soil/ composted organic matter needed annually even if the soil is dug. Can be expensive.

Learning Outcomes

1. Selection of site1.1 State the factors to be considered when selecting a site for outdoor food production;

including soil depth, texture and structure, drainage, pH, aspect, slope, susceptibility to frost and wind, area of land available and availability of water.

1.2 Describe the reasons for providing shelter for an outdoor food production area; including the effects of wind reduction, frost potential and influences upon pollination.

1.3 State the benefits and limitations of living and non-living windbreaks. 1.4 Name FOUR plant species suitable for a living windbreak 1.5 Name FOUR types of non-living permeable windbreak. 2. Cultivation techniques2.1 Describe a range of soil cultivation suitable for the vegetable garden: including digging

rotary cultivation, consolidation and tilth production 2.2 Describe how the timing of soil cultivations will be influenced by soil texture, structure,

weather and climate. 2.3 Describe what is meant by the bed system for growing vegetables. Compare this with open

ground production 2.4 Describe what is meant by a raised bed, giving a specification for a typical raised bed and

paths. 2.5 Explain the no-dig system of managing raised beds.