Agriculture in Hot Arid Environments (DP IB Geography)
Revision Note
Agriculture Opportunities & Challenges in Hot Arid Areas
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
Irrigation in Hot Arid Areas
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
Salinisation Risk
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
Examiner Tip
Do not confuse aridity with infertility. Many soils in the desert are potentially fertile, as they have minerals and nutrients within them. All they need is water to activate them. Although the Nile basin in Egypt is arid, the soil has rich alluvial deposits from the Nile flooding each year.
Land Ownership
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
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