I am in Florida, perhaps a little closer to your climate.
I am also in the irrigation business.
We bury our 1" line with a "ground saw" It cuts a 2" wide trench up to 13" deep and piles the lose dirt next to the ditch. If you have any roots to go through, the saw cuts them also.
If there are no roots to deal with, a "vibra-plow" (or pipe-puller) is another way to go. It will pull the pipe in to a depth about 15" without leaving a ditch to fill.
You should be able to rent either from a good rental place.
If the pipe is going to be in an area that is driven over and your soil is or gets soft (like when it rains), you may want to use the backhoe to bury the pipe so you can lay it 24" or so. That will protect the pipe from the weight of things driving over it.
One other thought ... if you think you will ever need to find that line in the future and are concerned that you may not remember exactly where it runs, bury a single strand buriable wire along with the pipe with a small coil at each end where the pipe ends. This way, a "locator" can be used to locate the pipe run in the future.