tractorhouse.com -> sprayers -> pull type
TractorHouse.com | Pull Type Sprayers For Sale - 1516 Listings - Page 1.
i might encourage just a general sprayer. granted i would more likely see the sprayers for actual spraying chemicals on fields. but... from sounds of it you are spraying a field of trees! just change out some boom hoses, and remove some other nozzles from booms. and go down the rows, spraying water were you want it.
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tractorhouse.com -> manure -> liquid
TractorHouse.com | Liquid Manure Spreaders For Sale - 579 Listings - Page 1.
ya i know odd, but there tend to be pure tanks listed, with maybe some sort of simple "boom" directly on the rear.
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google "septic tank"
ya i know another odd ball. but over years only search terms i been able to come up with, that will get me to websites / dealers that actually sell large size tanks. and search terms so far hold true over the years.
but once you start looking at various dealer websites, you can get into other types of water tanks. heck even a septic tank might work and many times come with baffles inside. (though maybe not baffles you want).
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you can always get a generic "sprayer" make it a skid sprayer, 3pt hitch sprayer, pull behind / trailer sprayer. and then hook up a larger tank to it. to get you more "volume" of water to work with.
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is there already a "pumping station" per say at the pond, to fill up with water?
or do you need room on trailer to haul around a gas trash pump?
along with do you need to haul suction hoses with trailer, to deal with getting water from pond?
height difference between top of water (lowest pond generally gets in summer), to top of water tank/s on trailer?
or are you looking at some sort of "PTO" driven pump? that is able to handle some solids? to suck water from pond and dump it into your tank/s?
are you making custom booms or some sort of setup to help water trees, or manually getting out and dealing with some hoses to water trees?
are you just going to toss a water tank on a regular car hauler or skid steer or like trailer, and go at it?
above questions, more geared towards, trying to figure out what you want in the end, to meet your needs.