Water

• Water is used in physiological functions of all living cells.
• Water is important for nutrient absorption - from soil as ions dissolved in water
• water is used to transport materials such as glucose, oxygen, and mineral nutrients
• water is needed to replace the water that is lost in transpiration

  water is drawn to the leaves carrying nutrients from the roots .
• water is needed for gasous exchange

  the stomata will close to prevent dehydration and die.

  the plant may survive but gas exchange will stop and growth will stop
• the amount of water available to plants is affected by precipitation rates and soil properties such as

  • permeability
  • water retention
• the hydrological growing season is the time during the year that there is suffient rainfall to support plant growth
• Reliability is needed for plant growth so farmers can plan what to plant and when. some areas struggle to plant crops due to unreliable seasonal rainfall and lack of other water supplies for irrigation.
• The quality of water can cause problems

  • a high salt content can cause salinisation leading to osmotic dehydration
  • heavy metals may bioaccumulate in crops and be a theat to human life
• problems caused by waterlogged soil

  • risk of fungal diseases
  • less soil fertility due to soil being anaerobic
• methods to reduce soil water levels are

  • excavation of drainage ditches or installation of drainage pipes
  • deep ploughing
  • avoidance of soil compaction by machinery or livestock
  • provision of soil conditions
• problems caused by water shortages

  • photosynthesis will stop as no carbon dioxide will be absorbed. If this prolongs the plant will die because of dehydration- inhibits cellular biochemical reactions
  • livestock will die- they will increase tampling damage on dry soils - could increase the risk of erosion and desertification
• Methods used to increase water availability

  • crop irrigation;
  • soil mulching to reduce evaporation losses from the soil surface
  • provition of sutible conditions for worms to increase infiltration and reduce run off
  • adding soil organic matter for water retention