being in Minnesota... and dealing with frost line... ground freezes in winter (raises unevenly in winter) and then thaws unevenly in spring.
ground that is not compacted good. is more likely to hold more water in it. and more likely to shift about throughout the year.
overall water drainage throughout the yard can have effects on the soil.
tractor / riding lawn mower itself has an overall effect. i really truly dis-like riding lawn mowers.... if you mow for a bit and hope off of it. your entire body feels like it is vibrating even through your off the tractor, vibration from engine and then lack of no suspension at all. you hit a bump and you feel it in your rear. minus some seat springs / seat cushion. and the faster you go... the more like the riding lawn mower becomes a bucking bull trying to toss you off of it.
simply messing with the first couple inches of top soil may not resolve issue. there may be bigger issue further down when it comes with compaction and then compaction of the soil as it gets closer to the surface.
i tend to rip up a pretty big area, when fixing yard from when i make ruts in it. both a few inches deep and wide a few extra feet around it.
old garden areas... when i was in grade school. dad moved the old garden a few times around the farm, and then a few years back a couple different places a garden was put in. each time it was moved it took some time to work out those bumps. it was not simply tilling it up and smoothing it out. it was working the soil at the right time... as in not to dry and not to wet. the big issue from get go is primarly ripping out all the roots from previous plants, along with breaking all the clods of dirt. i do not need "sand fine dirt" but 1/2" to 1" is fine with me. then i work around rains with ground drying out. to smooth things out.
clay soil likes to "slide" kinda like snot when it is wet. but can dry out like concrete it seems at times. example of to wet... would be ever dealing with trenches. for electrical, sewer, gas, telephone, etc... or simply digging a hole for say an in ground pool or goldfish/ koi pond. if you get a rain the gets that soil wet enough you end up with cave in's as sides fall in. granted you are on flat ground. but the issue is you are still dealing with "wet soil" and if you hope on tractor when it is to wet you can leave miniature ruts per say in the yard.
if i swap things around yet again on say dirt road on farm the one is right at 3/4 of mile long. i can look at it from car/truck/tractor seat and it looks perfectly smooth. then i get out on hands and knees and get a better view... and it can be filled with little bumps all over the place. from me fixing ruts to maybe a extreme heavy rain and a washout to pot hole forming, to other. i can hammer the dirt i can till the dirt, i can smooth the dirt over and over again. but again if it is to wet i just make a mess, if it is to dry i never do anything expect wasting fuel and wear / tear on myself and tractor and implements. there is a time of initial working the dirt road (fixing issues) and then a couple times after that were i need to weight almost when it is dried out when i need to go "SLOW" and run over the dirt road a few times to compact the dirt a bit better. this is about time when the R1's or R4 tires barely leave an indent in the dirt road.
dirt / gravel roads / driveway on farm has taught me a few things along with reading on internet. "wash board effect" driving way to fast. "pedal to the metal and through the floor board". slower down. and when the soil is wet slower down even more. fast speeds = weight of tractor shifting between all 4 tires. causing "mini compaction areas" or small little indents into the ground were compaction has happened more. again "clay soils likes to slide" and the dirt may not actual "compact" but rather "mushroom out / bowl out" creating a low spot in center and displacing that soil to hill up around the low spot, causing the soil to come up as a mini hill around the tires forming an even deeper /bigger bump once things dry out to much.
--other words kinda like digging a hole in yard (trench or something) and tossing all the dirt up along the sides of the trench. same like idea but as weight shifts around on all 4 tires on tractor. each tire acts like a hammer / digging a trench.
