High-tech irrigation methods, such as sprinkler and drip, no doubt save large quantities of irrigation water, but people are reluctant to adopt these systems because of their high installation cost, complexity, energy-intensive, need of highly skilled labour to operate, monitoring and maintaining the system.

It is imperative to introduce and encourage efficient, low-cost, simple, local-made, farmer-friendly and easy to operate and maintain sub-surface irrigation methods viable for small scale (1-2 acres) irrigation in Thar, Cholistan and Kohistan areas.

Due to high surface evaporation rates, subsurface irrigation is best suited for these areas. One of the small scale subsurface irrigation methods viable for arid areas is the pitcher irrigation method which has so far been ignored by most of the national and international developmental programmes.

Pitcher irrigation is an ancient irrigation system believed to have originated in China, as it is mentioned in a Chinese book written some 2000 years ago. This method is said to be one of the most efficient traditional systems of irrigation known which is well suited for small scale farming in many arid areas of the world. The method reportedly has been used to irrigate water melons and bottle gourd in India and Pakistan; horticultural crops in Brazil, Germany and Indonesia; and corn, tomato and okra in Zimbabwe. In Latin American countries such as Mexico, Brazil, and Bolivia, pitcher irrigation have a significant impact on small and medium scale cultivation. Pitcher irrigation is most suitable for areas where

Water is either scarce or expensive. Where surface evaporation rate is too high. Where land is difficult to level such as under uneven terrain and where soils are light textured with high infiltration rates.

Where water is saline which cannot be normally used in surface irrigation methods and in remote areas where fresh vegetables are either expensive or difficult to supply.

A pitcher is a round earthen baked pot usually used in villages for water storage and cooling, ranging from 10-15 litres in capacity. Pitcher wall is porous with millions of micro-pores from where water oozes out slowly when filled. When used for irrigation purpose, pitcher is buried in the soil down to neck and then filled with water. For this purpose, a pit of about three times as wide and two times as deep as the clay pot, is dug and the clods are broken at the bottom of the ditch. Manure is then mixed with the dug soil at a ratio of 13. If the soil is clay, then some sand is also mixed. When the soil is very sodic then mixing of some gypsum would be helpful in mitigating the sodium hazards.

Pitcher is then placed in the pit in such a way that the neck of the pitcher remains above the soil surface. Empty space around pitcher is properly filled with soil mix and firmed. Rim of the pitcher mouth may be painted with white paint to make it more visible. The pitcher is then filled with clean water as muddy water might block the pitcher pores. In order to avoid evaporation and breeding of mosquitoes, baked clay lid is placed on the mouth of the pitcher. Water seeps out through the micro-pores by the action of inside static water pressure head and outside soil matrix potential. In a day or two when the soil in the vicinity of the pitcher becomes visibly wet, then it is considered fit for sowing seeds and planting seedlings.

The seeds or plants are then placed within 0.5 to 4 cm of the outer edge of the buried clay pot. Six to eight seeds/seedlings are usually sown around the pitcher. Adding a small amount of water to the surface during sowing seeds and planting seedlings would be helpful to supplement early moisture and establish capillary action from the buried pitcher. A small space between plants should be left on one side of the pitcher for easier refilling of pitcher when the plants are fully-grown. Pitcher should be checked regularly to avoid drying. It should be refilled when 1/3 of water present in pitcher has been utilised. The refill period varies with stage of growth of plant soil type and climatic conditions. Small pitchers need frequent refilling whereas large ones may be refilled after one to two weeks.

Water seeps out from the pitcher wall as the water is taken up by plants. Thus, steady seepage from the pitcher maintains moisture content in root zone at field capacity (most suitable level of soil moisture content for plant growth) throughout entire plant growth period. At field capacity plants are able to absorb 100 per cent of their water requirements. Steady moisture level at field capacity increases crop growth and yield per unit application of water compared to that of traditional or high-tech irrigation methods.

The seepage of water as per plant requirement is also of great importance for sandy soils where water percolates quickly. Experiments conducted on sandy loam soil at the Sindh Agriculture University, Tandojam, showed that the crop production per acre was 2-3 times higher when bottle gourd and coriander were grown in sandy loam soil with pitcher irrigation method. Also 90 per cent of water was saved compared to traditional surface irrigation methods.

Figure Soil moisture distribution within root zone with pitcher irrigation method.

With this method of irrigation salt accumulates at the soil surface, leaving the salt content of water in the root zone more favourable than the salinity of water used in the pitcher. Tomatoes grown in Karnal, India with saline water having an electrical conductivity (EC) up to 12 dS/m (Indus water has EC from 0.2 to 0.4 dS/m) yielded 29 ton /hectare. Thus, even saline water can be used for irrigation purpose with pitcher method without any loss in yield. Soluble fertilisers can also be mixed with water and applied through the pitcher.

The spacing between pitchers mainly depends on the type of crop and the soil texture. For creeping type crops, spacing ranges from 2 to 2.5 meters whereas it should be 1-1.5 m for standing erect crops. Also light textured soils require close spacing compared to that with heavy textured soils. A creeping type crop requires about 1600-2000 pitchers per hectare of land whereas 4,000-5000 pitchers will be needed for standing erect crops.

Pitchers may need to be un-installed when the soil is to be tilled. During removal and re-installation process, they must be handled with care to avoid breakage. Also pitchers may clog up over time especially if left dry for a long time. Therefore, they need to be removed from the soil and reinstalled properly after scrubbing, or soaking, or re-firing to clean out the pores.

Pitcher irrigation is said most viable to arid regions because

It is cheaper and more reliable than many high tech irrigation systems. The whole system is made with locally available materials and skills.

As limited portions of land are irrigated, therefore, this system can save up to 90 per cent water compared to that of conventional irrigation methods. Agricultural production can be 2-3 times higher than that of with conventional irrigation methods. The cost benefit ratio can be as high as three. Crops can be grown at lower and higher air temperatures. Weed growth can be controlled. This method is helpful in agricultural propagation in salty soils. It is easy to install, operate and maintain. It can reduce fertiliser use, by allowing application only to defined, cultivated areas.

The prospects of pitcher irrigation are reasonably high in Thar, Cholistan and Kohistan areas where water scarcity and salinity limit cultivation. Saline groundwater can be pumped out with treadle pump and used for growing vegetables in these areas. Therefore, introduction and propagation of this technology will be helpful in changing the fate and face of the area by altering desert into oasis.