In Drip irrigation acid treatment can be continuously done to prevent the scale formation due to carbonate salts in the water. If these salts plug the emitters and pipe, reclamation by acid treatment becomes difficult. It is because the emitters will be discharging the water and it takes more time for removal of the salts. Hence, if the carbonate content is more than a critical level continuous treatment with acid for all irrigations is recommended.
Generally it is recommended that 1 litre of HCl should be done for 1000 litres of water. The acid treatment should be done for half an hour. The acid treatment should be done at the end of any irrigation. The water in the pipes should be left as such for overnight and next day the system should be flushed. During flushing first main lines should be flushed and then laterals. Otherwise, there will be possibility of emitters getting clogged with the removed scales.
Acids normally used are as follows:
Ø Hydrochloric acid ( 32% Strength)
Ø Sulphuric acid (93 % strength)
Ø Phosphoric acid (85 % strength)
Sulphuric acid is highly toxic and hence it is not used popularly.
Phosphoric acid should not be used if there is more than 50 ppm Ca in the irrigation water because calcium phosphate will precipitate. Calcium phosphate is nearly insoluble and does not readily dissolve.
Hydrochloric acid is very much commonly used.
Note : Always add acid to water and not water to acid.
See also:
Acid Treatment for Clogging Drippers / Emitters in Drip Irrigation
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