Subsurface Drip Irrigation System (SDI)

Rain-fed agriculture in Kenya is becoming increasingly unreliable especially in the drier areas where the issue is more about getting water, than it is about managing the water resources.

Thus in this article, we will explore an irrigation method that is centered on saving water and nutrients by allowing water to drip slowly to the roots of plants.

The Subsurface Drip Irrigation (SDI) system is a variation from conventional surface drip irrigation techniques in that laterals/pipes are buried beneath the ground.

Farmers all around the globe are quickly adopting this form of irrigated agriculture as a guard against uncertainties such as the amount and distribution of rain. In China, India, Israel and the USA, irrigated agriculture has widely been a magic bullet which has transformed the regions from net food importers to food exporters.

This technology has enabled a country such as Israel, a country that can fit into Garissa County twice, to feed the world. The SDI system is superior to the conventional methods of irrigation in various ways:

• High degree of uniformity of application as it is controlled by the output of each nozzle.
• Evaporation is reduced.
• The amount of water can be fine-tuned. This avoids water loss caused by runoff or evaporation.
• Frequent irrigation allows for optimum soil moisture content in the root zone.
• Great performance in windy and arid locations.
• If pre-treated wastewater is used for irrigation, the risk of direct contact with crops and labourers is reduced.
• Fertilizer and nutrient loss is minimized due to a localized application and reduced leaching.
• Field leveling is not necessary.
• Fields with irregular shapes are easily accommodated.
• Soil type plays a less important role in the frequency of irrigation.
• Soil erosion is lessened.
• Weed growth is lessened.
• Labour cost is less than other irrigation methods.
• Variation in supply can be regulated by regulating the valves and drippers.
• Fertigation can easily be included with minimal waste of fertilizers.
• Foliage remains dry, reducing the risk of disease.
• Usually operated at lower pressure than other types of pressurized irrigation, reducing energy costs.

How it works

Components used in SDI System (listed in order from water source) include:

• Pump or pressurized water source
• Water filter(s) or filtration systems: sand separator, Fertigation systems and chemigation equipment (optional)
• Backwash controller (Backflow prevention device)
• Pressure Control Valve (pressure regulator)
• Distribution lines (main larger diameter pipe, maybe secondary smaller, pipe fittings)
• Hand-operated, electronic, or hydraulic control valves and safety valves
• Smaller diameter polyethylene tube (often called “laterals”)
• Poly fittings and accessories (to make connections)
• Emitting devices at plants (emitter or dripper, micro spray head, inline dripper or inline drip tube)

Worth noting is that the layout of the pipes is done beneath the ground, the depth is dependent on tillage practices and type of crop to be irrigated.