Sustainable Agriculture Extension Manual

Smallholder drip irrigation

Crop failure from poor rains is widespread and on the increase in the East African drylands, leading to increased food insecurity. In the arid and semi-arid areas of Kenya, some form of irrigation is necessary to meet water needs of horticultural crops. Large, capital-intensive irrigation projects tend to perform poorly compared to smallholder-irrigation schemes. Poor management results in the unfair distribution of water, and in soils becoming waterlogged and saline, leading to some schemes being abandoned.

Three types of irrigation systems are commonly used: surface, sprinkler and drip irrigation. Drip irrigation is the most efficient in terms of water use. It provides good water control by delivering water near the plant, enabling the farmer to grow crops with much less water than with other methods. In drip irrigation, water flows through a filter into special drip pipes, with emitters located at different spacings. Water is discharged through the emitters directly into the soil near the plants through a special slow-release technology.

Location

Drip irrigation is especially useful where rainfall is unreliable or water supplies are present but limited.

Advantages

  • For a relatively low initial investment (US $15 to $85) a small-scale farmer can buy and set up a drip-irrigation system. If used to grow crops for market, this investment will pay itself within the first season and lead to increased household food production, especially during extended dry periods.
  • Drip irrigation requires little water compared to other irrigation methods. About 40-80 litres per day are needed per 100-200 plants.
  • The small amount of water reduces weed growth and limits the leaching of plant nutrients down in the soil.
  • Inorganic fertilizer or manure tea can be applied efficiently to the plants through the drip system.

Disadvantages

  • Most drip-irrigation equipment must be imported, so is not widely available.
  • Most experience in using drip irrigation is confined to commercial farmers and research stations.
  • Drip-irrigation systems are subject to clogging, especially if poor-quality water is used.
  • Farmers require training to manage drip irrigation successfully.

Requirements

  • Filter, drip tape or polyethylene pipe and drip emitters, connectors.
  • Water source (for direct-connected systems) or reservoir such as 20-litre bucket or 100-200-litre drum.
  • Material for constructing bucket-stand or platform for drum or water tank.

Bucket system

The bucket system consists of two drip lines, each 15-30 m long, and a 20-litre bucket for holding water. Each of the drip lines is connected to a filter to remove any particles that may clog the drip nozzles. The bucket is supported on a bucket stand, with the bottom of the bucket at least 1 m above the planting surface. One bucket system requires 2-4 buckets of water per day and can irrigate 100-200 plants with a spacing of 30 cm between the rows. For crops such as onions or carrots, the number of plants can be as many as the bed can accommodate. A bucket system currently costs about KSh 900 (US$ 15). A farmer growing for the market can usually recover this investment within the first crop season.

 

Bucket drip-irrigation system

Drum system

The drum system is a combination of several bucket systems but modified to use a water supply from a 100-200-litre drum instead of a 20-litre bucket. It consists of drip lines measuring 15-30 m long, a lateral line to which the driplines are connected (including a gate valve) and a drum or a small tank as the water reservoir, raised 1 m above the soil. The equivalent of five to ten bucket kits can be connected in this system. The lateral line is made of 2.5 cm (1-inch) diameter PVC, steel or polyethylene pipes. Connecting tees are used for each pair of drip lines.

A drum system equivalent to five bucket systems can irrigate 500-1000 plants planted with 30 cm between the rows. Such a system requires about 100-200 litres of water a day, depending on the environment and crop. It costs a total of KSh 5,000 (US$ 85). For comparison, a crop of cabbage yields a gross return of KSh 15,000 (US$ 250).

Bucket systems are produced by Chapin Watermatics Inc, 740 Water St, Watertown, NY 13601, USA, and are distributed at low cost. Bucket, drum, one-eighth-acre garden, and orchard kits are currently being promoted by the Kenya Agricultural Research Institute (KARI). For more information, contact Isaya Sijali, KARI.

Drum drip-irrigation system

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