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Drip irrigation

Objective:

Description

Drip irrigation allows for the optimal usage of water and fertilizers through their application close to crop roots. This is achieved by delivering small water flows at low pressure through a variable number of emission points, called drippers, and at a high application rate, which saves water. Water is saved in two ways: it is made to seep into the soil without evaporating or running off, and it is delivered at the root zone, just where the plants need it. The system is easy to design and set up and it generally consists of a water source, a pumping unit, a fertilization unit, filters, the distribution network and the drippers.

Location

Drip irrigation systems are suited for both flat and inclined fields because they do not cause erosion. They are particularly useful in areas with a prolonged dry season that have a reliable water source, such as a reservoir, and there is an interest in increasing yields or lengthening cultivation periods by rationally using water. If there is sufficient difference in height between the water source and the field, distribution may be gravity-based rather than pump-based.

Threats and Impacts it Addresses

The effects on crops of drought, extreme heat and changing rainfall patterns may be mitigated with drip irrigation systems through the efficient water use. The water savings allows production to continue where and when less water is available, which increases food security.

Implementation Steps

  1. Identify the crop and the area of the farm in which drip irrigation will be set up.
  2. Analyse the soil characteristics and the amount of water needed for the crops.
  3. Design the system with the aid of a technician.
  4. Assemble the system, including excavating the trench, laying the pipes, constructing structures for the different elements (pumps, filters, water tanks) and installing drippers at the irrigation points in the network.
  5. Carry out system maintenance, ensuring that the drippers do not get clogged by suspended or dissolved solids in the water.

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Inputs and Costs

The costs given below are for the adaptation of one hectare of land with drip irrigation. The main inputs are the materials for the distribution network, including the pump, the filtering and fertilizing systems and the drip line. The cost of labour for installation is also considerable. Three days of training in system operation and maintenance are assumed.

Drip irrigation, 1 ha US$
Labour 525
Materials 4320
Training 180
Total 5025

Economic and Ecosystemic Benefits

The primary ecosystemic benefit is efficient water use. Drip systems have been able to reduce water consumption by up to 70% compared with conventional irrigation systems. This is because plants receive the exact amount of water they require for optimal growth (FINTRAC, 2001). In addition, producers’ incomes rise by as much as 35% as a result of the higher yields stemming from efficient fertilizer usage, or "fertirrigation", i.e., the controlled application of nutrients with irrigation water. Another example is a comparative study of cotton cultivation which found that the gross margin per hectare was US$ 60 higher with drip irrigation than with sprinkler irrigation, using the same dosage of fertilizer. The same study reports that drip irrigation effectively applied 27% more water to the plants than did the conventional sprinkler system (Dippenaar and others, 1997)

Limiting Factors

The initial investment is high due to the quantity of materials to be purchased, and for an automated system the outlay is even larger. If improperly installed, the system may result in water deficiencies and the poor development of roots and plants. For this reason, assistance should be received from a qualified technician. There is a high risk of obstruction of the emitters and consequently of uneven irrigation. Hence it is necessary to include a filtering system suitable for the characteristics of the water used.

Learned Lessons

Some producers have designed low-cost sand filters made with locally available materials. Covering the soil with organic matter (crop residue or green manures) helps preserve moisture and provides additional nutrients to the soil, thus increasing irrigation efficiency. The most successful cases are obtained when farmers have a clear understanding of the technical characteristics of the system and of the crop’s water requirements.

Additional Considerations

Drip irrigation may be complemented by other cultivation measures like integrated pest management, integrated nutrient management, hydroponics and organic agriculture to increase output and the market value of the crops. In particular, when this technique is combined with the installation of a greenhouse, a highly efficient productive system able to compete on the market is obtained.

Units to Monitor Project Progress: Systems installed (number), area with drip irrigation (ha).

Unites to Monitor Measure's Impact: Productivity increase (%, t/ha); reduction in water consumption (%, m3).

References

  • Karmeli, D., G. Peri and M. Todes (1983). Irrigation Systems: Design and Operation. Oxford: Oxford University Press.
  • Keller, J. and R. Bliesner (1990). Sprinkle and Trickle Irrigation. New York: Nostrand Reinhold.
  • FINTRAC (2001). Programa de Riego por Goteo: resultados reales para personas reales. Programa de riego por goteo del Centro de Desarrollo de Agronegocios, CDA. Honduras: FINTRAC, March.
  • Dippenaar, M., C. Barnard and M. Pretorius (1997). “Yield and gross margin of cotton under drip and sprinkle irrigation”. Applied Plant Science vol. 11, No. 1, pp. 7-12.