We had a day off yesterday when we had another icy spitting sleety day. We took advantage and headed to the laundromat to wash 7 loads, and to the truck stop to take two showers!
So today was the day that we rented a tiller to tackle the garden beds.
We've been watching the thaw line in our lower bed inch its way south day by day as the sun is higher in the southern sky. Still, more than half of the lower bed is solidly frozen. There are also some tree shadows in the upper bed, keeping the ground frozen in those spots, and the other areas are also frozen a few inches down. We've tested some areas with a pitchfork and pickaxe, but it's hard and slow going, and Chip wanted to give the tiller a go.
We are ready to put up the frame for our greenhouse. This was our last chance to dig in the upper greenhouse beds while standing up, because once the greenhouse is built, those raised beds will be under the greenhouse glazing, and close to the framing. So we went ahead and rented the tiller even though the timing was not ideal.
Chip did all of the tilling. The machine is powerful and awkward -- you have to let go of the handle to engage the tiller, which lurches it forward. The handle grips were also loose so that once it even drove itself out of Chip's hand, leaving him holding the grip before he jumped after it. It is also belt-driven and the old belt was loose and came off a couple times. Rented equipment is always a challenge. In their defense, the store was not expecting to rent out the tiller in January, and hadn't done their spring maintenance yet.
Anyway, both Chip and I were fine letting him take on that job -- I'll have to pay back by doing more of the slow hand-tilling when the beds are enclosed and warm, which is what I had been pushing for! Chip took several passes on all of the upper beds, and the more thawed part of the lower bed, too. He did get it to dig down a foot in most places, which was quite good, considering. It was not fun, but he pushed through uncomplainingly, as always.
While Chip tilled, I pulled together our soil amendments. I powdered the dry horse manure by running it through the chipper (thank goodness horses don't carry hantavirus, but I imagine the amount of manure I breathed in was probably not great for me anyway). I spread 10 gallons of horse manure on the south bed, 3 gallons of nitrogen-infused wood chips, 3 gallons of coffee grounds, 3 gallons of wood ash. I used about half that on the narrower north bed, except that we didn't have any more manure. We'll have to gather a ton more of that. The other amendments all came with cautions -- wood chips take nitrogen to break down, coffee is too acidic, ash is too alkaline. There's so much contradictory info about amounts and how to use them, and the one thing online resources agree on is that you have to test your soil to see what it needs. We just know that our soil needs a boatload of organic material, so we are making our best guess, gathering what we can, and throwing it in. We'll wait a month and test the soil at that point and see where to go from there...
Chip ran the tiller over the amended beds one last time to mix things in.

Excellent, Bruce! Thank you for this footwork! We definitely want to do worm composting but haven't even bothered to look up local resources, because the worms won't like winter camping... once the greenhouse is underway, we'll be ready to roll, and now we'll know where to go!
Worms in New Mexico! https://bernalilloextension.nmsu.edu/mastercomposter/composting-worms.html
All black soil comes from earthworms. Earthworm soil is pH balanced. It looks like there are lots of worm farmers in your area.