Question 1: Vegetation Control

My wife and I planted approx 500 black walnuts seedlings on our property in 2015, the year we were married. We had some extra "field" at the back of our property (approx 1.25 ac) and thought this would be a neat and meaningful way to start our marriage. We cut down the field grass and light brush and planted bare rooting seedling that were 6-10 inches tall. It's been 7 years and our walnut grove is really taking shape. Some of our finest specimens are well over 12' tall and 2.5-3" DBH. We have done no irrigation and only started vegetation control around year 4. We did lose quite a few due to the lack of management. I'd say we lost around 30-40%, which was on the high end of our expectations. We did 2 rounds of replanting in year 3 and year 5 to replace some of the lost trees. This has left us with a wide range of sizes in our grove. The replantings done in year 5 are still quite small (12-20" tall) and dwarf in comparison to the original plantings. Here's my question: what size diameter around the stem should we be controlling vegetation and at what point is it no longer benefit to control the vegetation? We had been spraying 3-ft diameter but I am wondering if that is still necessary for our larger trees. If there is a benefit, I would gladly continue doing it. Spraying is probably the easiest part of managing our grove. It's the pruning that takes days and days to perform. For us, a labor of love :)

Question 2: Tree Spacing

Our walnut grove is planted with approx 7x7 spacing. At the time of planting we read somewhere that this was ideal for timber production. However, I just read that you recommend 8x10 spacing. Do you suggest we transplant trees to thin the herd? We have the machinery to transplant trees while leaving a small root ball in tact (approx 18x18x18"). If it's between cutting the trees down or attempting a transplant I'd prefer to give that a shot. We have some larger areas where trees died that could be planted with transplants.

Thanks for reading all this and for sharing your wisdom with us all.