Manual Irrigation

Manual irrigation systems are easy to handle, require no technical equipment and are therefore generally cheap (in contrast to high-tech systems such as sprinkler irrigation or subsurface drip irrigation). But they need high labour inputs. A common and very simple technique for manual irrigation is for instance the use of watering cans as it can be found in peri-urban agriculture around large cities in some African countries. A more sophisticated and very water-efficient type of manual irrigation system is small-scale drip irrigation with buckets (see also drip irrigation). Beside these systems, there are many other methods for manual irrigation, which are easy to install and simple to use. In general, all of these methods have high self-help compatibility and a relatively high performance. Therefore such systems are also called HELPFUL irrigation methods: High-frequency, Efficient, Low-volume, Partial-area, Farm-Unit, and Low-cost (FAO 1997).

Low-Cost Drip Irrigation System

Simple drip irrigation (in contrary to high tech drip irrigation systems) uses low-cost plastic pipes cut to the appropriate lengths laid on the ground to irrigate vegetables, field crops and orchards. Small holes in the hose allow water to drip out and keep the base of the plant wet without wasting any water. Read more about it here.

Watering Cans

Irrigation by watering cans is a very basic way but is still widely used.This creates a lot of work for the labours especially if this technique is used for large fields. A common way to make this work easier is a carry-pole across the shoulders. The field worker is able to carry two big watering cans in each side and the irrigation water can de distributed equally on the field. A rose can be added to the watering-can to create a “sprinkler effect” (see picture).

With watering cans, the field worker is able to irrigate very specific and only where it is necessary.

Pitcher Irrigation

(Adapted from: FAO 1997 and INFONET-BIOVISION 2010)

A very basic subsurface (see also subsurface drip irrigation) method consists in placing porous clay jars (or pots) in shallow pits dug for this purpose. Soil is then packed around the necks of the jars so that their rims protrude a few centimetres above the ground surface. Water is poured into the jars either by hand or by means of a flexible hose connected to a water source. Since the walls of the pots are porous (make sure to use unglazed pots), the water can seep slowly out and reach the roots of the plants. The jars can be made of locally available clay: they are of no standard shape, size, wall thickness or porosity. Instead of a clay or earthenware pod, also the sweet monkey orange fruit (Strychnos spinosa) can be used when it has been dried and the top cut off. The jar should be filled up regularly (especially in arid areas) and has to be changed if there are big cracks that the water percolates without reaching the roots.

Bottle Irrigation

(Adapted from INFONET-BIOVISION 2010)

Similar to the pot method described above, pitcher irrigation can also be done using a bottle. The bottle is first filled and than placed with its neck into the soil next to a plant, so it stands upside down (see picture above). The dense soil hinders the water from leaving the bottle immediately. Instead, it gets released slowly and directly besides the roots, so it is available to the plant for a longer time and the water cannot evaporate directly.

Porous and Sectioned Pipes

(Adapted from FAO 1997)

Another variation of pitcher irrigation uses porous pipes instead of pots to spread water along a continuous horizontal band in the soil, rather than at discrete locations. As such, the porous pipe method is more suitable for closely spaced row crops grown in beds, such as vegetable crops. One end of the porous pipe is made protrude above ground that the operator is able to refill it with water as soon as it is necessary. In contrast to subsurface drip irrigation, the porous pipe distributes the water over the whole length and not only where it is perforated. That means it is less effective and water loss is slightly higher.

Perforated Plastic Sleeves

(Adapted from FAO 1997)

An interesting variation of the pitcher method is the use of thin plastic sheeting to form a sleeve-like casing. To define its comparative usefulness better, the method should be tested side by side with alternative methods of irrigation. To date, this has not been done systematically.

All of the described systems are very cheap. Many of them can be made out easily available material (e.g. old buckets or bottles) or renewable resources (bamboo). This reduces the costs significantly. However, high labour inputs are required for operation and maintenance.

As water is brought into the system manually, this requires high labour input. Moreover, it is important to check the systems regularly to prevent blockages and leakages. If there are any problems it should be cleaned and/or fixed as fast as possible to prevent damages on crops. Furthermore, there are several techniques to improve the production and avoid water loss on the fields. See crop selection.

(Adapted from TILLEY et al. 2014)

If wastewater is used for the manual irrigation process, there are potential health risks if water is not properly pre-treated (i.e. inadequate pathogen reduction). If poorly treated wastewater is applied. Appropriate pre-treatment should precede any irrigation scheme to limit health risks to those who come in contact with the water. As well, depending on the degree of treatment that the effluent has undergone, it may be contaminated with the different chemicals that are discharged into the system. When effluent is used for irrigation, households and industries connected to the system should be made aware of the products that are and are not appropriate for discharging into the system. Drip irrigation and subsurface drip irrigation are the only types of irrigation that should be used with edible crops, and even then, care should be taken to prevent workers and harvested crops from coming in contact with the treated effluent. Despite safety concerns, irrigation with effluent is an effective way to recycle nutrients and water (see also fertigation or waterborne diseases pathogens and contaminants).