Agriculture in Hot Arid Environments (SL IB Geography)

• As long as water is available, the heat and sunlight in hot, dry regions allow for an extended growing season
• Alluvium deposits provide nutrient-rich, fine soils that warm up quickly, but they are at risk from wind erosion and flash floods
• A type of nomadism is still the most common way to farm
  
  • True nomads move around with their animals, looking for new places to graze all year round
  • Many are semi-nomadic, where they move their flocks and herds but have a settled home to take advantage of higher levels of supplies near villages and towns
  • With the increase in desertification and water scarcity, many people have become sedentary and have settled permanently in villages, towns and cities

• Oases, desalination plants and exotic rivers provide opportunities for settled agriculture
  • Egypt is the largest producer of dates in the world
  • Date palms are known as the ‘bread of the desert’
  • They can be eaten and the Bedouins use dates to make bread
  • They are a traditional medicine for swelling and coughs
  • The bark can be used for roofing and fencing and the leaves can be plaited into ropes and mats
  • The Aswan dam ensures the Nile provides a continued supply of water throughout the year
• In a number of oil-rich countries, such as Saudi Arabia and the UAE, desalination plants provide constant water supplies
  • However, these have environmental impacts and are very energy-intensive 
  • Desalination produces brine, which is extremely salty water, and is returned it to the sea, raising the salinity of the surrounding water
  • Due to the costs involved in producing the fresh water, desalination-produced food is more expensive
• Agriculture in hot areas could be more sustainable by:
  • Planting vegetation that is drought-resistant or salt-tolerant for animal feed
  • Reducing the size of herds will limit the pressure on vegetation
  • Using animal dung as fertiliser
  • Using solar panels to produce energy 
  • Using efficient forms of irrigation, such as drip irrigation
  • Building small-scale dams and micro-hydro's

• The lack of water in dry areas is usually the limiting factor in agriculture
• Irrigation is typically used to support natural rain fall, but a regular water supply is hard to come by in hot, arid areas
• Also, high temperatures and strong sunlight cause water to evaporate quickly, adding to water scarcity
• Natural water sources can be diverted using:
  • Advanced irrigation systems such as irrigation channels, weirs and small dams, but the large surface areas leads to high rates of evaporation, plus they are not cheap to build or maintain
  • Flood irrigation is where farmers deliberately flow water over their crops. This is a low-tech but wasteful method of irrigation
  • Spray irrigation supplies water through a centre pivot sprinkler system
  • Drip or micro-irrigation, is a planned irrigation system where water is applied directly to the root zone of plants either above or below the soil, by applicators
• Hydroponics uses 90% less water to grow crops, but the system is expensive to set up
  • With this method, plants get all the nutrients they need from special solutions and do not need soil
  • Crops grow twice as fast as in traditional farming
  • Light, temperature and water are more controlled and monitored than plants grown in soil
  • Crops are also pesticide-free
  • Systems can be run on solar energy

• Hot arid climates are characterised with low mean annual precipitation
• Leaving the soil with a negative water balance
  • Output is high due to rapid and continued evaporation and transpiration
  • Stores of water are typically large (aquifers) but deeper than the root zones of plants
  • Input is low through brief periods of heavy precipitation, leading to
    • Rapid runoff
    • Low rates of infiltration
    • Reduced soil water recharge
  • Therefore, desert soils are arid (dry) but potentially fertile (if water is added, the minerals and nutrients are released and the plants can access them)
• Other factors contribute to arid soils and include:
  • Low organic content from limited biomass
  • Low clay levels
  • Thin topsoil layer
  • High levels of soluble salts due to a lack of leaching
• Salinisation is where intense evaporation at the soil's surface encourages soil moisture and minerals to rise 
• This leaves the soil with a high pH value
• When irrigation water is added to the land and allowed to evaporate, this increases the effect of salinisation
• Increased soil salinity restricts most plant growth by reducing water uptake by plant roots
• Some crops are more salt-tolerant than others and are called halophytes 
  • Palm dates and cotton are halophytic

Examples of salinisation

• Salinisation has made a lot of land in the Thar desert of Pakistan infertile
• Irrigation should always be done with drainage where salinisation is a risk
• In Pakistan, 13% of all irrigated agricultural soils were classified as strongly saline, totalling some 6.8 megahectares (Mha)
• In India, this secondary salinisation has become a serious problem
• The use of large irrigation schemes, many without effective drainage plans, has changed and disturbed the water balance in many parts of the once fertile lands of Uttar Pradesh state and inside the Indo-Gangetic plains
• Salinisation and alkanisation have affected 5.26 Mha of land in India

• Deserts provide opportunities for large-scale commercial agriculture with the availability of large expanses of unused land, long growing season and soils with nutrients
• For areas that rely on farming as their main source of income, land ownership is important for families to succeed and survive
• Land ownership disputes can arise between indigenous populations, government entities, and private companies
• The competition for control over agricultural land increases because of the major role it plays in securing water rights
• Furthermore, competition also increases socio-economic inequalities and perpetuates gender disparities, as traditionally, land is owned by men and women face obstacles in accessing and owning land