Old 07-17-2013, 10:21 AM
cactus cactus is offline
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Production Rates for Backpack Sprayer

Looking for a sanity check on some math. I'm trying to estimate a production rate for applying organic products (humates, seaweed, compost tea, etc) using a backpack sprayer.

Assuming I have a 4-gal backpack sprayer, it sprays about 1/4-gal per minute and I'm expecting to apply 1-gal of tank mix per 1000 sq-ft:

I'm guessing it takes about 5 minutes to measure product and fill the tank (mixing on-site from concentrate), and I think that I can cover ground enough that I'm limited by my sprayer output, not my walking speed - so call it 4 minutes per 1000 sq-ft to spray.

So my math says that for a 5000 sq-ft area, I'll need 2 tank fills (10 min) and 20 minutes application time = 30 minutes total (plus time to cleanup, etc.)

Thirty minutes sounds like a long time for a 5000 sq-ft area, but maybe not. I'm new to this as a business, and while I've applied plenty of product before, it's always been at home or volunteer maintenance at a church, so I've not bothered to track how long it takes.

Thoughts or comments? It may be that I need to adjust my tank mix so that I'm applying less than 1 gal/1000 - that's just the guide I've usually used for my organic applications. Also, how unprofessional is it to mix onsite using the client's water? Should I bring my own water or pre-mix before arriving?

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Old 07-17-2013, 10:39 AM
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foreplease foreplease is offline
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Location: St. Joseph, MI
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I spray chemicals and no organics. That said, your math looks fine in the sense you have added and multiplied correctly. I believe you can cover 1,000 square feet faster than 4 minutes though if your sprayer's output will keep up.

Do you need that kind of water volume to get your organics through the nozzle? I do not know but it seems very high.

Edit: I understood you to say it takes you 4 gallons of mix to cover 1,000 feet. My mistake. 1 gallon per thousand is ok but I think you should be able to move along more quickly.
Michigan PABL

Last edited by foreplease; 07-17-2013 at 10:42 AM. Reason: Misunderstood
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Old 07-17-2013, 11:15 AM
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phasthound phasthound is online now
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Should I bring my own water or pre-mix before arriving?

When applying compost tea, chlorinated water will diminish the microbial activity. If it is chlorinated add humates first to neutralize it.
Barry Draycott

The nation that destroys its soil destroys itself.
Franklin D. Roosevelt
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Old 07-17-2013, 11:32 AM
cactus cactus is offline
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Thanks for the replies.

My practice is to fill the tank with water and then add humates to complex the chloramine. I add the CT after I've stirred the tank a couple of times.

I don't need a high carrier volume to flow the products, but I do want to make sure that the CT is put down with enough water that the microbes don't dry out before they find a place to call home. With humates, seaweed extract, and the like, I could use less carrier and put it down even faster, perhaps. But so far I've kept everything the same (walking pace, application rate, etc.) for all my applications.

If I ever decide to put down blanket applications of something more critical, I'll probably need to revise and practice my technique.
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Old 07-17-2013, 03:54 PM
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RigglePLC RigglePLC is offline
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I suggest using a dry granular organic product. You could save a lot of time. If you can manage a swath width of 11 feet 4 inches, you will cover 3000 sqft per minute (at 3 mph). 5000 sqft in a minute and 36 seconds.
Or if you can manage 3.4 miles per hour spreader walking speed with a swath of 10 feet you will cover 3000 sqft per minute.

I am sure Barry can suggest an organic product that would suit your soil type and equipment situation. Maybe Screamin' Green would fit your needs.
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Old 07-17-2013, 04:43 PM
cactus cactus is offline
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Thanks for the input.

Based on a couple of numbers I ran, granular v. liquid came out about the same for the products I'm looking at using. Liquid pray takes longer, but costs less (per unit area). Granular goes down faster, but costs more.

Two things limit my rate on the granular with a push-spreader: (1) Small yards, lots of obstacles and (2) My current spreader only has a 50-lb hopper - that only hold about 40 lbs of the larger prill organics that I've been using. Maybe if I get a larger hopper I'll reduce my time a bit (fewer refills), but I don't see a huge difference in overall costs with the products I'm sourcing and the equipment I intend to start with.
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