Site selection

Question 1

Factors to consider in site selection

Answer 1

• Soil:
  
  • Depth
    
    • need reasonable depth to allow for unimpeded root growth, most plants occupy top 40cm of soil
    • important for carrots and parsnips which have long tap roots
    • enables good root establishment of fruit trees and bushes
  • Texture (how soil feels)
    
    • clay soil will be hard to work, can become water logged, is slow to warm in spring, but retains nutrients well, good for growing brassicas. Should be cultivated in autumn to enable frosts to break down clods
    • sandy soil is free draining, will warm fast in spring but will dry out quickly, good for root crops. Should be cultivated in spring to avoid leaching of nutrients
    • Loam soil good for growing range of vegetables
  • Structure (make up of air, water, organic matter)
    
    • Sandy soils free draining so compaction less of an issue in winter. Tilth production may result in soils surface capping after irrigation.
    • Clay soils become waterlogged and compacted.
      
      • Restriction of gaseous exchange at root level
      • May reduce root’s ability to access nutrients
      • Restricted development of root crops
  • pH
    
    • most plants need neutral pH of 6.5-7.0. Widest range of nutrients available for uptake by plants.
    • Acidic soil with pH 5.5-6.5 is ideal for blueberries
    • Alkaline soil with pH 7.0-7.5 is ideal for brassicas to avoid club root
  • Drainage
    
    • Adequate drain essential for provision of aeration and good root growth. Also allows soil to be easily cultivated.
    • Sandy soils may be too free draining and lead to crop desiccation, require addition of bulky organic matter to retain moisture and prevent leaching of nutrients
    • Clay soils are prone to waterlogging, may require a full drainage system to overcome this
• Wind - light winds reduce crop yields by 20-30%, wind can cause damage to crops e.g. fruit trees
• Frost/air drainage - avoid frost pocket e.g. at the base of a slope and avoid planting fruit trees in frost prone sites as will damage blossom/fruitlets. Frost will damage seedlings and soil will be slower to warm in spring.
• Aspect and slope
  
  • level site is best for vegetables but a small south-facing slope will have most light intensity and have more light in winter when sun is low in sky, soil will warm earlier in spring
  • sloping site harder to work than flat one. Steep slope should be terraced to make it easier to work and reduce soil erosion due to water run off
  • It will be dry at top of slope and wet at bottom
  • Frost pockets may occur as base of slope
• Availability of water
  
  • May need to install water butts
  • Lack of water will result in poor and/or reduced crop yield.
• Area of land available
  
  • Small area will limit choice of crops that can be grown, will make rotation of beds more difficult, but is better suited to raised beds
  • Large area more suitable for crop rotation, will enable machinery to be used, could include permanent crops e.g. fruit trees, asparagus

Question 2

Reasons for providing shelter for an outdoor vegetable growing area

Answer 2

• Wind reduction:
  
  • wind can reduce vegetable crop production by 20-30%
  • Can blow over crop supports e.g. runner bean poles
  • Can damage crops e.g. blow over brassicas, blow fruit from trees, damage trees
  • Windrock of shallow rooted plants
  • Desiccate (loss of moisture) crops
  • Reduces soil erosion
• Frost potential
  
  • frost kills fruit and flower buds, kills/damages emerging seedlings and burns leaves
• Influences on pollination
  
  • exposure to wind discourages pollinating insects from flying which results in in reduced size and regularity of fruit crops.
• Creates microclimate
• Prevents soil erosion

Question 3

Name plant species suitable for living wind break

Answer 3

• Fagus sylvatica (beech)
• Carpinus betulus (hornbeam)
• Crataegus monogyna (hawthorn)
• Alnus glutinosa (Alder)
• Taxus baccata (Yew) - evergreen

Question 4

Examples of non-living permeable windbreak

Answer 4

• Paraweb (plastic strips)
• Trellis
• Woven hurdles
• Hit and miss fencing
• Open patterned brick wall
• Plastic mesh e.g. Rokolene

Question 5

Windbreaks and shelterbelts

Answer 5

• Windbreaks and shelterbelts are semi-permeable barriers that reduce wind speed and provide shelter for plants.
• To be effective, windbreaks must be semi-permeable, ideally filtering 50-60% of the wind to reduce its strength
• A windbreak will significantly reduce wind on its leeward side to a distance of ten times its height.
• Should face the prevailing winds
• Reduces soil erosion

Question 6

Benefits and limitations of living windbreaks

Answer 6

• Benefits
  
  • Provides habitat for wildlife and beneficial organisms e.g. birds
  • Filters wind, rather than stopping it (which would force it over the top) resulting in reduced crop damage on leeward side
  • Long lived
  • Aesthetically pleasing
• Limitations
  
  • Take time to establish
  • Require regular maintenance
  • Compete with crops of water and nutrients
  • May harbour pests and diseases
  • Take up more space than non-living windbreak

Question 7

Benefits and limitations of non-living windbreaks

Answer 7

• Benefits
  
  • Quick and easy to erect, give immediate protection
  • Take up less space than a hedge
  • Do not compete with cultivated plants for water and nutrients
  • Low maintenance
• Limitations
  
  • Require maintenance and may need replacing before a hedge
  • Can be expensive to buy and erect

Question 8

Benefits of providing shelter in an apple orchard

Answer 8

• Avoids physical damage to trees e.g. broken branches, toppled trees and wind rock to roots
• Avoids fruit blown from trees
• Prevents wind scorch to leaves
• Prevents damage/loss of blossom during flowering period
• Allows improved pollination as bees do not fly in windy conditions
• Avoids increased loss of water by transpiration
• Provides shelter for natural predators
• Provides warmer conditions for better quality fruit and higher yields

Question 9

Benefits and limitations of rotary cultivation

Answer 9

• Benefits
  
  • Less labour intensive than digging
  • Easier for large areas
  • Buries annual weeds
  • Incorporates fertiliser and organic matter
  • Creates tilth on uncultivated land
• Limitations
  
  • Chops up and distributes perennial weeds
  • Creates a rotovation pan
  • Destroys structure of top soil
  • Unsuitable for raised or narrow beds
  • Some machines heavy and difficult to use in small areas