the purpose of agricultural irrigation and the advantages and disadvantages of mainstream methods

Irrigation is defined as the artificial application of water to the soil through various systems of tubes, pumps, and sprayers.  Approximately 20% of the world’s agricultural land is irrigated, yet 40% of the world food supply comes from irrigated lands with 70% of the world’s freshwater reserves being used for irrigation purposes.  

The main reasons for irrigation are:

1. Not enough rainfall to support crop growth.  

This may be due to rainy and dry seasons, drought or arid/semi-arid climate conditions.  Irrigation systems may also be used to maintain consistent moisture levels even in areas with moderate precipitation levels as it has been shown to improve crop performance.

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2. High soil salinity levels.  

High soil salinity levels can be a natural occurrence which is the case in many semi-arid and arid locations or a result of poor agricultural practices and ineffective drainage.  In cases impacted by salt levels in the soil, irrigation must often be coupled with drainage in order to achieve the desired benefits.  

There are two main types of agricultural irrigation – gravity powered and pressure driven systems.  Gravity powered systems are, as the name implies, driven by gravity.  Pressure driven systems require an electrical pump in order to provide the irrigation system with water.

Examples of gravity powered systems include:

• Furrow irrigation systems, basin irrigation systems and hand irrigation systems.

Advantages of Gravity Powered Irrigation Systems

• Low-cost – gravity is free and simple irrigation systems can be developed to use this wonder of physics
• Promotes social interaction – many community members need to work together to ensure the success of irrigation systems, particularly those dependent on water that comes from long distances (ex. mountain runoff)
• Can be used indefinitely as long as the irrigation system is well-maintained

Disadvantages of Gravity Powered Irrigation Systems

• Requires constant monitoring to ensure that the crops are not damaged by too much/too little irrigation water
• Difficult to adapt to the specific needs of plants

Examples of pressure powered irrigation systems include:

• Drip irrigation systems, sprinkler irrigation systems and pivot irrigation systems.

Advantages of Pressure Powered Irrigation Systems

• High water efficiency
• Very adaptable to the needs of the plants which allows a wider variety of crops to be grown – especially those of higher value

Disadvantages of Pressure Powered Irrigation Systems

• High use and maintenance costs (parts replacement, electricity costs)
• Expensive to install
• Requires a high level of education and training for use (the most advanced system in the world can be installed, but if the people don’t know how to use it, it’s useless.)
• Needs to be replaced every 10 – 20 years as the technology becomes outdated