Debris on the diskmower.  I have run them and am well aware of what they are capable of.  There are tree limb's 6" in diameter.  There are oak 2"x6" 20 feet long.  I road a 4 wheeler across on field this afternoon just crawling along I hit a 6" diameter limb before I saw it.  The heavy crop will make it difficult with a rotary mower (bush hog).  Much of the debris will be too large to rake with a wheel rake also.  I was involved in a commercial hay operation for many years.  I understand what hay equipment is capable of.