Ranks Country/Region

Subirrigation also known as seepage irrigation, is a method of irrigation where water is delivered to the plant root zone. The excess may be collected for reuse.

Manual irrigation

Water is distributed across land through manual labor and watering cans. This system is very labor intensive

Manual irrigation is by far the most common form of irrigation as anyone physically able to, can manually irrigate their crops. Manual irrigation is you moving water from plant to plant. This is very labour and time intensive and is usually done with a hose or bucket, so it is only suitable for smaller areas

1. 
   For watering large areas of farmland, drip irrigation is the most efficient irrigation system for reducing water and fertilizer loss. By filtering the water down through the soil and into the root system, some of the water percolates down into the groundwater system to be reused for irrigating in future years.
   
2. 
   Surface irrigation is the oldest form of irrigation and has been in use for thousands of years. In surface ( flood, or level basin) irrigation systems, water moves across the surface of an agricultural lands, in order to wet it and infiltrate into the soil.
   
3. 
   Irrigation schemes in the world use about 3 500 km3 water per year, of which 74% is evaporated by the crops. This is some 80% of all water used by mankind (4 400 km3 per year).
   
4. 
   Improper drip irrigation installation often culminates into poor root development and dieback. For example, looping your tubing too wide or installing a small quantity of water emitters creates drought conditions where roots continually grow – they may resort to shallow growth to find moisture and die back.
   
5. 
   Furrow or flood irrigation is widely used in many parts of the world, including the US, but is the least efficient, losing about 50 percent of water applied. This loss can be reduced by leveling fields, practicing surge flooding and capturing and reusing runoff.
   
6. 
   Indonesia tops the chart showing countries with the largest overall area, with 225,000 square kilometres taken by permanent cropland, or 12.4% of its total. Second on the list is China, with 160,000 sq km – some 1.7% of its total land area.
   
7. 
   Unlike other forms of irrigation, such as sprinklers that are only 65-75% efficient, drip irrigation 90% efficient at allowing plants to use the water applied. And, it reduces runoff and evaporation. Drip irrigation applies the water slowly at the plant root zone where it is needed most.