Super99, Irrigation systems do cost and there are sur-enough issues.......
Water:::: Amount, Depth, how strong. In the Panhandle in the 80s if your well was strong enough to handle 80 acres of row water, Full irrigation Corn,,,then you well would handle a 120 acre, 1/4 mile sprinkler,,,, 800 gallons/minuet +. -->+++.
Lay of the land Usually on pretty flat but that doesn't mean a thing ,,,for a regulator can be put on just above each nozzelle <(ms) They will only allow so many gallons/minuet go through so it allows the entire length of main pipe to stay full and not have soupy wet places or desert dry others.
Tow-able /non Tow-able,If you have 40 acres that will handle a sprinkler, You will soon discover an adjacent 40 acres that can be cleaned up with some land leveling, and shaping so you get 2, 40 acre fields in play for the initial investment of 1 machine.
A tow-able would probably be you first preference. 1 machine, 2 pivot pads, and underground to each from your well/wells gets you going. Usually in the past most farmers I knew bought tow-ables first off. 1/4 milers, so one machine could water a circle of summer crop and a circle of winter wheat or oats.
The problem with that is in the spring when corn needs to be up and going you may need one last round to finish off wheat before cutting. Many farmers get tired of doing this dance, So after a few yrs most farmers will start filling the vacant circles with Non-tow machines so that head ache of moving machines in between 2 crops doesn't have to be messed with. At that time all you have to do is open up one valve and close the other is the hardest work in changing water from one crop to another/
Also Pivot pressure Has come down over the yrs, Those old Water Drives required 90 + lbs at the pivot to operate. Now most have gone to Ultra low pivot pressures <20 lbs. the wear and tear on pumps. is waaaay less.
Micro switches and how a system stays in line when in a run operation.
I will allow changing a flat tire on a tower is brutal but has to be done from time to time.
NEVER, NEVER, NEVER park a tractor, truck, Combine over a Sprinkler track or in the path where an on comming sprinkler is running. You forget about it and Sur-ernough a sprinkler will walk, crawl all over it,, it knows no stop. Vehicle damages and sprinkler crashed.
As Far a sprinklers go ONLY 3 word says it all,....Its a VALLEY!!! enough said.
Go educate your self, Visit with local farmers about their wells, and machines, Local Dealers!!!
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At first I would say stay away from a used machine. Until you get really educated on what you are thinking on doing. and then look only at Galvanized units, Run backward from old raw painted steel units,
Hope this helps.
Later,
John A.