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RHS Level 2 Certificate
Week 18- Outdoor food production. Site selection and cultivation methods
Quiz
8 questions – test conditions
30 minutes
Learning Outcomes
Site selection State the factors to be considered when selecting a site for
outdoor food production in a garden situation Describe the reasons for providing shelter for an outdoor food
production area in a garden. Compare the advantages and disadvantages of using natural and
artificial windbreaks. 2. Cultivation techniques Describe a range of soil cultivation techniques used in outdoor
food production. Describe the methods used to advance and extend the
productive season of outdoor food crops. State the benefits and limitations of the use of the bed system in
outdoor crop production.
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;
Wall Attractive and permanent. Expensive and hard to put up
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.
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 usually slightly raised 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.
Learning Outcomes
Site selection State the factors to be considered when selecting a site for outdoor
food production in a garden situation Describe the reasons for providing shelter for an outdoor food
production area in a garden. Compare the advantages and disadvantages of using natural and
artificial windbreaks. 2. Cultivation techniques Describe a range of soil cultivation techniques used in outdoor food
production. Describe the methods used to advance and extend the productive
season of outdoor food crops. State the benefits and limitations of the use of the bed system in
outdoor crop production.