CLOGGING AND MAINTENANCE OF MICRO IRRIGATION SYSTEMS - Management, Performance, and Applications of Micro Irrigation Systems - page 95

Acid is usually injected after the fi lter so that it does not corrode the fi lter. If the
fi lter is made of polyethylene, which resists corrosion, acid can be injected before the
fi lter. The amount of acid to use depends on the characteristics of the acid you are us-
ing and the chemical characteristics of the irrigation water. A titration curve of the well
water used for drip irrigation can be developed by a laboratory showing the amount of
acid needed to reduce the pH to a certain level. If a titration curve is not available, use
a trial and-error approach until the pH is reduced to 6.5. Colorimetric kits or portable
pH meters can be used to determine the water pH at the end of lines. Many farmers
inject 1 to 5 gallons of sulfuric acid per hour, depending on the water pH, water qual-
ity, and well capacity.
Most chemicals used in drip system maintenance are extremely hazardous. Sulfuric
acid is very corrosive and must be handled with proper personal protection equipment.
Store sulfuric acid in polyethylene or stainless steel tanks with extra heavy walls. Al-
ways add acid to water; do not add water to acid. Never mix acid and chlorine or store
them together in the same room; a toxic gas will form.
Besides clearing clogged emitters, acid injected into irrigation water may improve
infi ltration characteristics of some soils and releases micronutrients by lowering the
soil pH. To reduce the cost, acid can be injected during the last third of the irrigation
time.
7.2.6 ADDITIONAL NECESSARY MAINTENANCE
7.2.6.1 KEEP OUT PLANT ROOTS
It is important to keep plant roots from penetrating the drip emitters (Fig. 4 shows a
root intrusion problem). Metam sodium and trifluralin are two compounds that control
roots. In cotton, metam sodium is generally used at defoliation to keep roots out as
the soil dries, while trifluralin is used before harvest. Super-chlorination at a dosage
of 400 ppm chlorine also will keep roots out. Fill the tapes with chlorine and leave it
overnight.