Drip line servicing major need
Maintenance of drip irrigation lines may not be the most exciting job in a vineyard. Okay, it’s not even very interesting. However, keeping drip lines operating trouble free has a direct impact on your bottom line.
“A lot of people don’t maintain their drip lines and the lines fail within three years. Ours have been up for 10 years and still aren’t ready to be replaced,” says Bob Clifton, irrigation supervisor for Coastal Valley Management in King City, Calif.
Clifton isn’t bragging. He’s just pointing out the savings possible when growers dedicate themselves to maintenance.
Clifton maintains his lines by flushing them three times a year. Clifton employs a three-approach system. He uses chlorine to clear out algae and bacteria, phosphoric acid to supply phosphorus and to lower water pH, and N-pHuric fertilizer to also lower water pH and to supply nitrogen and sulfur.
“The chlorine does a good job on organic matter, the phos acid is good for areas that need phosphorus, and the N-pHuric is great on silt and calcium deposits,” reports Clifton.
“Silt is just clay particles, and they like to attach to the diaphragm of emitters,” he explains. “The N-pHuric fertilizer breaks up that film buildup.”
Each of the three products has its use, says Clifton.
Chlorine has long been used as a treatment for excess organic matter. It and copper are the only biocides most experts recommend, although there are specialty products that are useful in certain situations. Chlorine comes in three forms: chlorine gas, sodium hypochlorite (bleach), and calcium hypochlorite. Chlorine gas is the most efficient and easiest to use but is extremely dangerous if a release occurs. Sodium hypochlorite is easy to handle and safe but degrades over time so it needs to be used within a month or two of delivery. Calcium hypochlorite delivers a high level of available chlorine (65 percent) but must be dissolved and may cause precipitates. Clifton uses sodium hypochiorite.
The N-pHuric fertilizer is strongly acidic and is often used as a remedy for water with a high pH and/or high buffering capacity. Clifton gets his water from wells and says quality is excellent. Even so, he says, he will get a buildup of precipitates if he doesn’t treat the water. “It’s like platelets in your arteries,” he says.
Strong acids break up precipitates by breaking their chemical bonds. The most common precipitate in the West is calcium carbonate (limestone). This is formed when bicarbonates or carbonates combine with calcium. Not only does this lead to limestone deposits, it ties up the calcium and allows sodium to remain in the soil surface and root zone. Dissolving limestone releases calcium, which in turn displaces sodium from the clay particles and allows it to leach below the root zone.
It also improves water infiltration and aeration since calcium is known for bringing soil particles into aggregate. “It definitely has an effect on friability,” confirms Clifton.
N-pHuric fertilizer also supplies nitrogen and sulfur to grapes.
Phosphoric acid
Phosphoric acid is a moderately strong acid that is a common sight in Western agriculture. Again, its acidity is used to lower water pH, to break up precipitate bonds and to provide better water infiltration. And it supplies phosphorus. Clifton estimates he uses phosphoric acid on 10 percent of his acres.
“I use it wherever my vines need phosphorus; otherwise I use N-pHuric. I go by soil and petiole test results to know which product to use,” he says.
It and other acids also make other nutrients available. Calcium becomes available, as limestone bonds are broken. And by bringing water pH below 7.0, acids also make pH-sensitive nutrients available. Phosphorus, iron, zinc, manganese and magnesium, in particular, tie up in high-pH soils.
A final note about acids: Lowering the pH of water to a proper level increases the effectiveness of chlorine. When injected, free chlorine consists of hypochiorous acid (HOCl) and hypochlorite (OCl). Hypochlorous acid is 40 to 80 times the biocide that hypochlorite is, so it’s important to keep the ratio of HOCl to OCl high. In water with a pH of 6.0, nearly 90 percent of the free chlorine will be HOCl. At a water pH of 8.5, only 10 to 15 percent is HOCI.
In his drip lines, Clifton Won’t use fertilizers in suspension. As he explains, “Gypsum or some other product in suspension is fine unless you shut down or if you don’t have constant velocity. When that water stops, those particles in suspension can settle out. And they always seem to go to the worst place in the drip lines. Then, when you go to start up, you have a real mess. I know. I’ve seen it happen enough that I use liquid fertilizers now.”
In the high-pH soils of the West, chlorosis can become a problem in vines.
“Iron, zinc, and magnesium are among the nutrients that tie up as soil pH approaches 8.0,” explains Larry Odell, district sales manager for Prodica, Fresno, Calif. “Chlorosis often is called iron chlorosis because it frequently is caused by an iron deficiency. However, it can also be zinc chlorosis or magnesium chlorosis.”
N-pHuric fertilizer is used throughout the West to eliminate chlorosis in trees and vines. To clear up chlorosis, N-pHuric fertilizer may be shanked into the soil six inches deep and a couple of feet out from the rootstock. Or it can be dripped in through drip irrigation. The effects are usually seen within one week, says Odell.
In one trial, N-pHuric fertilizer was compared to UAN32 in a row crop situation. Even though UAN32 is an acidifier in itself, N-pHuric fertilizer had a stronger effect. Soil pH was above 8.0. A total of 190 units of nitrogen was injected during the course of the trial. In the soil zone 0 to 6 inches deep and 7.5 inches on either side of the injection, N-pHuric fertilizer dropped soil pH below 7.5 in the entire area. In the same UAN32 zone, lowered soil pH below 7.5 in just the top inch of soil.
“After several applications, similar pH benefits can be achieved in permanent crop settings,” notes Odell.
Grape growers who have water that is high in pH and/or bicarbonate can adopt one of two methods. They can use an acid fertilizer continuously to maintain lines, or they can use it intermittently to flush out the systems.
The following recommendations for low-volume systems are from Prodica, manufacturers of N-pHuric acid fertilizer.
For continuous water treatment, Prodica recommends lowering the water pH to around 6.0 to 6.5 and maintaining it at all times when water is being applied. Doing so will remove some 50 percent to 66 percent of the bicarbonate in the water. That, in turn, will improve water infiltration and make pH-sensitive nutrients available to vines.
To flush irrigation lines, Prodica recommends lowering the water pH to 4.5 if the system contains metal components and to 2.5 to 3.0 if it contains corrosion-resistant materials. The water should be held in the lines for three to six hours, longer if the pH is 4.5 or higher. The ends of the lines should be opened and the system flushed with untreated water following the injection of N-pHuric fertilizer. The system should be treated a time or two each season or whenever it becomes plugged.
In both situations, it is important to obtain a buffer demand curve for a grower’s specific water source. It is also recommended that a grower manually check the pH of the treated water at the end of the line.
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