Figure 6: Sprinkler irrigation Figure 7: Travelling Sprinkler irrigation

♤ Sub-irrigation: Sub-irrigation also sometimes called seepage irrigation has been used for many years in field crops in areas with high water tables. It is a method of artificially raising

the water table to allow the soil to be moistened from below the plants' root zone. Often those systems are located on permanent grasslands in lowlands or river valleys and combined with drainage infrastructure. A system of pumping stations, canals, weirs and gates allows it to increase or decrease the water level in a network of ditches and thereby control the water table. Sub-irrigation is also used in commercial greenhouse production, usually for potted plants. Water is delivered from below, absorbed upwards, and the excess collected for recycling. Three basic types of sub-irrigation are: ebb-and-flow, trough, and flooded floor.

There are various challenges to adopt these localized forms of irrigation. Few of them are listed below:

♤ Expense: initial cost can be more than overhead systems.

♤ Waste: the sun can affect the tubes used for drip irrigation, shortening their usable life.

♤ Clogging: if the water is not properly filtered and the equipment not properly maintained, it can result in clogging.

♤ Waste of water, time and harvest, if not installed properly. These systems require careful study of all the relevant factors like land topography, soil, water, crop and agro-climatic conditions, and suitability of drip irrigation system and its components.