So how do you get an old hay field ready for planting? This field has been growing hay (mixed vegetation) for over 30 years with frequent fertilization and so has a wide array of mixed native and non-native species …..some particularly problematic invasive species included.
The grass mat formed on top of the soils provides pretty healthy competition for plants so just popping the trees into the field would be both difficult (hard to get a tree spade thru) and would result in the trees being out competed by grasses.
We wanted to give the trees a head start against the non-native vegetation and so we tilled the field using a large disc attachment on a plow. As budget permits we will till each years section the fall before and then plant in the spring.
Why fall tilling? Partly because the soils are relatively dry after the growing season and the tractor can move easily within the area without getting bogged down (presuming we get a window between the end of the growing season and fall/winter precipitation) — this simple one-pass till essentially flips the top layer of the soil over in furrows. We also plant in the fall because winter seed dispersers like birch will have a chance to to deposit seed on a nice host layer of soil and will have an easier time getting established than in a dense mat of grasses.
Note: When we plant, we plant either in the bottom of the furrow or right on the hinge as the very top often dries out too quickly.