USDA-ARS Northwest Irrigation & Soils Research Lab Station Note #01-98
Determining The Oil-Emulsion PAM (30% AI) Application Rate For Head Ditch or Pipe Flow
R.D. Lentz and R.E. Sojka
USDA-Agricultural Research Service
INSTRUCTIONS:Determine the PAM concentration desired in the head ditch or pipe flow. The standard method applies 10 ppm PAM to irrigation inflows from the beginning of the irrigation until water advances to the end of the field and begins to run off. After this advance phase, the PAM injection is stopped, and untreated water is run for the remainder of the set. In some cases, an irrigation water PAM content < 10 ppm may be satisfactory. Find your total head ditch or pipe flow rate on the horizontal axis and move up/down until you intersect the diagonal line corresponding to the desired PAM concentration in the irrigation water. Then move horizontally toward the right axis to find the PAM-product application rate in fluid-ounces/minute. Adjust for active ingredient (AI) concentration. Example and computational details are presented on the back page .
EXAMPLE: Suppose your are an irrigator who has 50 miners inches (= 448 gpm, Idaho) of water flowing in the head ditch and wishes to treat the flow with 10 ppm. How much oil-emulsion PAM containing 30% active ingredient (30% AI) should be metered into the flow to attain the target concentration of 10 ppm PAM? Since the head ditch flow is known in miners inches we would enter the chart along the bottom horizontal axis at 50 miners inches. Next, move straight up until you intersect the diagonal line corresponding to 10 ppm Target PAM Concentration. Then move horizontally, toward either the left or right vertical axis, depending on the units with which you desire the answer reported. If, after intersecting the 10 ppm diagonal line, you move toward the left axis, the answer is given as 53.5 mL/minute. If you move to toward right axis, the answer is given as 1.8 fluid-ounces/minute. Therefore, to attain a PAM concentration of 10 ppm in a flow of 50 miners inches, you must meter 53.5 mL emulsion-PAM / minute or 1.8 fluid-ounces Emulsion-PAM/minute into the head ditch stream. If product's active ingredient concentration is substantially different than 30%, you should adjust the application rate. This is done by multiplying the rate by the fraction (30/AI), where AI is the percent active ingredient in the product (by weight).For example, if the PAM product was 50% Al (instead of 30%), the adjusted PAM application rate for the above example would be:
CALCULATING PAM APPLICATION RATES
FOR DITCH/PIPE FLOWRATES AND PAM CONCENTRATIONS BEYOND THE CHART RANGE:
The following formula can be used to compute PAM application rates for any ditch flowrate and target PAM concentration desired.
Oil-emulsion PAM (30% AI) application rate (mL/min) to head ditch or gated pipe flow =
(Target PAM conc. in ppm [= mg/L]) x (head ditch or pipe flow in Idaho miners in.) x
(8.96 gpm/miners in.) x (3.785 L/gal) x (0.001g/mg) x (3.145 mL emulsion-PAM/g PAM).
To adjust the rate for the product's active concentration, multiply by the fraction 30/AI, where AI is the percent active ingredient in the product (by weight)
To convert from mL/min to ounces (fluid) per min, multiply the result by 0.03378 oz/mL.
revised Apr.23, 1998