You have the right idea for the creek to remedy that wet spot. A rough grade and culvert pipe is the way to do it. I'd recommend some riprap for the sides to keep the soil from the field washing in. As far as clearing you can do one of two things (except that leaner at the edge of the field. You could mulch the base of the big ones so you can push them over, or invest in some quality wood mats and work the mulcher or grapple just ahead of the edge of the mats.
It’s a thought I ran by him too. But he wants to just clear out the small brush for now. We plan on having around 100 cattle on the farm in the next 5 years.
