Site selection Flashcards
Factors to be considered when selecting a site for outdoor food production
Area (of Land Available)
Accessibility
Aspect
Availability of water
Slope
Susceptibility to frost and wind
Shade
Soil - Depth, Drainage, pH, Structure, Texture
Site suitability considerations for Area of land available
- window sill or large allotment
- make best use of space available
- e.g. veg plot, pottage garden, containers, raised beds, dwarf cultivars.
Site suitability considerations for Accessibility
- tools and resources close to hand
- easy access to site
- paths wide enough - deliveries?
- on-site storage - security?
- access to water
Site suitability considerations for Aspect
- direction to which site is open
- south-facing is best (North won’t get sun)
- sheltered, but open to air movement
Site suitability considerations for Availability of Water
- need water source - standpipe?
- run hosepipe - summer months
- have water butts for rainwater
Site suitability considerations for Slope
- level or slight southerly slope
- steeper slopes cause problems:
- rain can erode topsoil
- loses moisture and nutrients
- maintenance is gruelling!
- more exposure at top than lower down
- water drains downwards = water-logging and leaching of nutrients.
Site suitability considerations for Susceptibility to Frost and Wind
- Frost pockets damage fruit buds, fruitlets, seedlings, mature plants;
- Frost pockets form at base of slope, in areas of shade, by hedges across a slope.
- Wind damage - plants are sensitive to wind!
- Wind causes soil erosion - particles blown away;
- Wind causes plants to lose water - higher transpiration;
- Coastal winds case salt damage - scorch plants
Site suitability considerations for Shade
- site should not be overshadowed by trees or buildings - crops shaded from essential sunlight;
- there is extra warmth in area in front of south-facing wall - sunny spot!
Site suitability considerations for Soil TEXTURE
- sand, silt or clay?
- loamy, mixed soil is best for a wide range of plants;
- root veg like sandier soils (warm & good drainage)
- brassicas like more clay soil (but be careful of water-logging?!)
Site suitability considerations for Soil STRUCTURE
- how particles clump together
- poor structure is easily compacted, easily waterlogged and restricts root growth;
- air available?
- mixed crumb structure is idea - OM is essential - add in to improve structure;
- need high diversity of organisms - OM helps this!
- cultivation can help improve structure
Site suitability considerations for Soil DRAINAGE
- influenced by texture and structure;
- needs to be well aerated and well-drained, not prone to waterlogging, yet moisture retentive;
- waterlogging kills plants;
- artificial drainage or raised beds can remedy
Site suitability considerations for Soil DEPTH
- good depth important for root system of fruit trees;
- built-up beds or containers - raised beds?
- root crops need deeper soil;
- earth-up potatoes;
- 45cm ideal depth for fruit trees;
- 30cm ideal depth for veg plants.
Site suitability considerations for Soil pH
- pH affects how well plants take up mineral nutrients;
- may develop deficiencies if pH is inappropriate;
- pH of 6.5 to 7.0 is suitable for most crops;
- blueberries and cranberries like a low pH;
- brassicas favour higher pH - up to 7.5 (protects against clubroot)
Reasons for providing shelter - influences on growth of crops
- limits damage by exposure to wind (leaf injury, branch injury, snapped stems, blown over, fruits knocked);
- limits water loss (wind = transpiration);
- insects less likely to fly in windy conditions - affects pollinators (BUT also pests!);
- limits frost damage to buds;
- provides warmth early and late in the year;
- provides microclimate - increases crop production.
Definition of a windbreak?
A semi-permeable barrier.
Examples of living windbreaks
Hedges filter and baffle wind
Shelterbelts - for larger sites - taller trees planted in 3-4 rows, offset - facing prevailing wind.
Examples of non-living windbreaks
Netting or plastic mesh (50-60cm high)
Paraweb (webbing) - taller screens over 1.5m
Hit & miss fencing (panels attached to alternate sides of posts)
Hurdles woven from willow or hazel - stakes or whips, woven dead or green - placed at angle to prevailing wind.
Trellis
Living windbreaks - Benefits (x4):
Look good - aesthetically pleasing
Long lasting
Habitat and food for wildlife
Encourages beneficial organisms
Living windbreaks - Limitations (x5):
Takes time to establish and grow - not an instant shelter!
Needs regular maintenance
May harbour pests and diseases
Takes up space
Can compete with crops
Non-living windbreaks - Benefits (x4):
Erects quickly with little effort
Provides instant protection
Low maintenance
Uses little space - good for smaller sites
No competition with crops for nutrients
Non-living windbreaks - Limitations (x3)
Don’t look as nice
Don’t last as long - e.g. fencing would need regular replacement
No benefit to wildlife
Examples of species for living windbreak (x5)
Fagus sylvatica
Taxus baccata
Ilex aquifolium
Carpinus betulus (Hornbeam)
Crataegus monogyna (Hawthorn)
List soil cultivation techniques suitable for vegetable garden
Single and double digging
Rotary cultivation
Consolidation
Tilth production
Describe single and double digging
Ideally in autumn or spring:
Single - remove one spit deep of soil, and invert.
Double - remove one spit deep of soil and work the second spit with fork, incorporating OM.
Describe rotary cultivation
Mechanical cultivation - less strenuous
In clay/wet, can compact or cause soil pan
In dry, can produce too fine a tilth
Remove perennial weeds - don’t chop in!
Describe tilth production
Secondary cultivation is the final stage of preparation to achieve a good soil - a good surface tilth
Fine seeds like a good tilth of small, even particles - a fine crumb (this retains moisture and nutrients - aids germination).
Don’t cultivate if soil is too wet/sticky/dry/dusty
After winter, quickly go over with fork/hoe/rake/manual cultivator - breaks up surface clods and uneven surface
Tramp lightly and rake surface in push-pull motion
Larger seeds can have a larger crumb
What influences the timing of soil cultivation?
Soil texture
Soil structure
Weather
Climate
Effects of weather on soil cultivation - inc. cultivation window
Too wet - will damage structure
Winter into spring - too wet?
Clay soils should never be worked when wet
Frozen - impossible to work
Later spring - cultivation can recommence
Timings are called the “cultivation window”
Window can vary - weather in north and south differ a lot
Window is shorter in the north - soil takes longer to warm up
Light, sandy or silty soils are better worked in the spring
Describe a bed system (layout etc)
Relatively small, separate beds in a garden or allotment
Laid out in patterns, so that there are pathways adjacent or through the bed
All parts of bed are accessible
Beds should be 1.5m wide and 3m long
Not necessary to step on soil
Warms quicker if beds are raised (e.g. 30cm)
Limitations of not using beds and just using open ground
Long parallel drills or rows (e.g. kitchen garden)
Access means walking on soil to maintain it
More likely need to cultivate each year to relieve compaction
Describe raised beds, including benefits
Typical raised bed is 1.5m wide and 3m long.
Paths in between must be at least 50cm wide (1m if wheelchair is used)
Bed height 30cm
Better drainage in raised bed, .˙. warms up quick in spring, due to raised height
Raised with walls - bricks or planks (with wooden pegs on outside) on side edges.
Filled with quality topsoil enriched with OM
Useful if plants require a specialised soil type different to underlying soil
Do not have to have edges - soil can be thrown-up, creating chamfered edge between bed and path
Can be built to any height - bricks are better when building high (can help disabled gardeners)
Benefits of “no-dig” method
Minimises problems associated with disturbing the soil, e.g.:
bringing weeds to surface
soil degradation - loss of stability
soil opened up, allowing in air and water
spread of pests and diseases between beds (result of walking on soil)
disturbance of organisms, e.g. worms
No walking on beds so no compaction
If beds are raised access is easy
Less soil maintenance - digging, weeding etc.
“No-dig” method
Mark out beds - include narrow path
Remove all weeds, esp. perennials
Double dig if necessary - incorporate BOM
Apply further OM to surface, to build up
If no weeds or no cultivation needed:
place layer of cardboard over surface**
water cardboard thoroughly (helps breakdown)
spread layer of OM over top, 10cm thick (holds down card and suppresses weeds)
Interplanting or green manures maintain a dense cover on ground
Stay on top of hand-weeding - be vigilant - weed around beds also!
Keep adding more OM to surface when depleted.
** Instead of cardboard, can use porous, woven black plastic (Mypex) - cut slits (crosses) and plant through these.
Benefits of advancing and extending the growing season
allows early sowing
protects plants from early frosts
brings on tender veg for planting out
allows late crops to continue and overwinter
Advancing/extending the season - main methods
Mulches
Fleece
Enviromesh
Perforated, clear poly sheeting
Cloches
Low tunnels
Cold frames
Warm soil over winter with black poly sheeting
Start off plants indoors or under glass for earlier vegetable harvest
Extending the season - describe the benefits of MULCHES + examples of organic & non-organic
These dress the top of the soil
Mulch when still warm and not water-logged!
- they insulate and help reduce evaporation
- they stop weed seeds growing
- they add nutrients and OM
Organic mulches:
- garden compost
- horse manure
- straw
- seaweed
Non-organic mulches:
- plastic sheeting - make slits
- decorative stone or gravel
Extending the season - describe the use of FLOATING MULCHES/FLEECE etc
Horticultural fleece is a spun plastic crop cover:
- insulates against frost
- light and loose
- different grades
- edges should be weighted down
Enviromesh is a woven plastic mesh netting:
- excludes flying insects (flies, butterflies, aphids)
- lasts longer than fleece but less frost protection
Poly sheeting - perforated, clear is not so useful!
- warms soil but doesn’t hold heat and can also overheat!
- no air/water exchange
Extending the season - describe CLOCHES and use of
Structures placed or built on top of plants
range of shapes, sizes and materials
glass, PVC, polycarbonate. metal or plastic frame
individual cloches can be as simple as a halved plastic bottle!
allows early spring start and later year protection
allows overwintering of suitable crops
protects from rain and wind
higher humidity - keeps warm
inexpensive, moveable, versatile
deters pests - rabbits, birds
Extending the season - describe LOW TUNNELS and the use of
Small polytunnels for a row of plants (hooped frames)
moved and dismantled easily
poly film can be pulled back in stages to harden plants off
can also be made using fleece
Extending the season - describe COLD FRAMES and the use of
Low frame made from wood, brick, aluminium
Glass or polycarbonate “lights” that can be raised or slid upwards to allow in air
Protects against rain and wind - also frost if insulated
Maintains a higher temperature and humidity
Acclimatises plants that have been overwintered in a greenhouse
Seeds can be sown earlier in the year
