One of the advantages of using pitchers for irrigation is the result of their water saving capacity. To compare pitcher irrigation to flood or sprinkler irrigation one must correct for the fact that the scales are radically different. Pitcher irrigation is used on small-scale, while flood and sprinkler systems are for moreextensive irrigation. Taking this into account, pitcher irrigation is still more efficient. Pitcher irrigation uses water more efficiently than other systems since it delivers water directly to plant root zones, instead of to broader areas of the field. With pitcher irrigation, deep percolation losses are negligible since water is released from smaller areas, and the rate of water loss can be controlled site to site by the amount of water put in each pitcher. Water requirements in a pitcher irrigated field can be even less than those of a drip irrigated system (of the same scale) due to the very low hydraulic conductivity of the pitchers, as well as reduced evaporation losses.
Research with pitcher irrigation at the Central Soil Salinity Research Institute (CSSRI) in Karnal India indicates that the amount of water which seeps out of the pots--and thus the number of plants which can be sustained by each pot--depends on the soil type, the porosity of the pot wall as well as the shape of the pot used. Pitchers are generally placed at distances so that wet areas do not overlap.
Soil moisture and salt distribution in the plant rootzone are much more favorable with pitcher irrigation than with any surface method of irrigation. Under pitcher irrigation salt accumulates at the soil surface, leaving the salt content of water in the rootzone more favorable than the salinity of water used in the pitcher. Thus even saline water can be used for irrigation in the pitcher irrigation system. Watermelon and muskmelon both tolerated water salinity levels of up to 12 dSm-1. A tomato crop yielded almost 29 t/ha at 12 dSm-1 with 5000 pots/ha. Note that water of good quality for irrigation has a conductivity below 2 dSm-1, while sea water has a conductivity of about 46 dSm-1.
Scientists at the Central Soil Salinity Research Institute have found that seven to ten litre pots are sufficient to grow most vegetable crops. The number of pitchers needed per hectare varies with the crop. At least four plants of most vegetable crops could be grown around one pot. A creeping crop such as bitter gourd required 2,000-2500 pitchers per hectare. Upright crops, or crops producing a canopy around the pot required more pots, up to 4,000-5000 pots per hectare.
The profitability of pitcher irrigation must consider the labor of acquiring, burying, and filling the pots, in addition to the labor involved in managing the crop. Researchers at CSSRI found that the most profitable crops for pitcher irrigation in that area were (in order) tomato> bottle-gourd> bitter-gourd> watermelon> cauliflower. The muskmelon was unprofitable, thus they do not recommend its cultivation with pitcher irrigation.
The prospects of pitcher irrigation are reasonably high, especially in areas where water scarcity and salinity limit cultivation. The only difficulty with this method is the high labor demand which it places on the farmer. Pitcher irrigation may be an inappropriate solution where the labor needed to set up and run the system would fall on already overworked laborers.
See Volume 1 # 1 of the International Ag-Sieve for a brief description of pitcher irrigation in Uruguay.
For more information and a copy of Pitcher Irrigation by R.C. Mondal, S.K. Gupta and S.K. Dubey, edited by H.K. Barthwal, Central Soil Salinity Research Institute, Karnal INDIA, Rakesh Press, 1987 contact:
R.C. Mondal, Director
Central Soil Salinity Research Institute