I've read many posts and a lot of product information about chemicals such as Cutrine plus, Reward, etc. and their application rates.

I think I understand the calculations to determine the appropriate total amount of chemical per surface acre, but still need some help mixing that much chemical with the right amount of water as I'm applying it.

If, for example, I need to treat 1 surface acre of water and the recommended rate is 2 Gallons of chemical per surface acre, and I have a 3-Gallon backpack sprayer, how do I determine the water:chemical mix ratio per 3-Gal "batch"? I don't think I can cover the 1-acre area with a single 3-gallon batch, it's more likely to take 5 batches based on my typical application method of "soaking" the mats of algae, for example. Do I just spread the 2 gallons of chemical over the 5 batches? I never know how heavy to apply the Cutrine, for example. So, that influences how much mix it takes to treat a certain amount of surface area.

Any help? What am I missing? I'm sure it's a simple calculation, but it escapes me. It feels like I'm overdoing some applications and under on others.

Thanks,
Dave

Ah, and an age-old question you pose.....
EPA guidelines for most herbicide registrations require that the use-rate be stated by "area" rather than "concentration". Therefore, many products will list a rate per-acre or per acre-foot of water rather than as a mixture-ratio.
Enter the term "calibration"; which is exactly what you alluded to in one of your earlier paragraphs.
In many cases, the dilution ratio in your mix tank is of less concern than the amount of actual product being applied to a specific area.
EX: When treating a 1-acre pond, there's virtually no difference between mixing 2 gallons of product XYZ into 10 gallons of water and applying that mixture to the 1-acre pond vs. mixing 2 gallons of XYZ into 20 gallons of water and applying that mixture to the 1-acre pond. Either way, you applied 2 gallon of XYZ to the 1-acre pond. Only your water-volume (carrier) was altered.
So, you're right on track with your earlier "question". Figure out how much water-volume (5 batches) you'll need to complete a treatment to a known area-size (1 acre). Then, add/split the specified amount of product (2 gal) to treat that area (1 acre) into the pre-determined amount of water-volume (5 batches).
When depth comes into play (as with CUTRINE), you simply multiply the acre-foot rate by the avg depth within the treatment area, while using the same application-volume concept discussed above.

Kelly,

Thanks!!! You simplified it considerably and I now know how to handle it. I really appreciate the quick response and also value your other posts. It's nice to have an expert in the family.

Off to spray...

Dave