I assume that you will be placing the irrigation pipe at least 6" below the surface, or more depending on where you live. I did a quick search and did not see a low priced trencher that would dig that deep. Most that I saw were heavy duty edgers.

It you need the trencher where I live you can rent a open trailer for about $20 per day, You could rent the trailer, pick up the trencher and have it and the trailer back in a day. again depending on the amount of trenches you have to dig.

If your back can handle it, a mattock can easily create a lot of trenches, quite quickly.

https://www.lowes.com/search?searchTerm=mattock

Unless one is planning on going into the irrigation installation business, there is no need to purchase a trencher - it won't be used enough to be cost effective. And the cheapo hand models are just that......cheap and ineffective. For about the same cost of purchasing one of the more or less useless lightweight hand models, you can rent a professional grade trencher that will do the job in a quarter of the time.

Fully agree with gardengal. Even if it seems more expensive to rent, at least you won't have to store it and throw it away someday.

One important thing to do when you remove soil from a trench is to put ALL the soil back into the trench when you're done. It will be mounded up at first but for the next 3 years, it will settle back down leaving a perfectly even surface. If you scatter the leftover soil around the yard, then in 3 years you'll have a new trench as the soil settles down.

Yeah, just rent a good one and rent the truck to haul it.

I did a quick search in my area, and several places will rent you the equipment, deliver it, and pick it up when you're done. The prices aren't quite as inexpensive as Home Depot, but the equipment also looks to range from somewhat better right up to professional quality. So if you're able to handle the equipment, it's an option that may be available in your area as well.

Personally, as a lifelong klutz...well...nobody wants the highly probable ER trip.