I still think though that there's no harm in having a spare tractor (and driver)
We do have a Massey 3125 as a sort of spare, trouble is we don't have 1000 speed PTO, so it won't run the mower, and the electrics aren't up to the baler.
When we were trying out a baler without wrapper the other wrapper had to be used separately, dad said he would go out wrapping after milking, hitched the wrapper up, changed the electical plug and went off out, ten minutes later I got a phonecall "Dan, how do you get this wrapper to work, it just did half a turn and then stopped" As someone who used the wrapper a lot I knew the spool lever on the tractor had popped out and shut off the oil flow, but as dad hasn't used it for years he had forgotten, and as such turned the wrapper control box off and on again, then the wrapper thought it was at the start of a cycle, but with the table in the wrong place, so I told him to put on manual and wrap using switches. An hour later I got a voicemail message "Dan, the tractor has died, it's late and I'm going to bed, have wrapped one bale." So, the following morning I go out to wrap bales, at the start I have a wrapper hitched to a dead tractor, with the electrical connectors changed, I would have been better off if we didn't have a spare. Different story if it worked though.
And that's the other problem with spare tractors, the price of them. We have just done a deal on a new tractor, and the 6465 is going rather than the 3125. 120hp, 5 years old, 4500 hours, mid spec, mint condition but tyres down, £31k. We couldn't keep that as a spare for 75 hours a year.
By the time you finish carting all those bales it'll be too late to apply slurry before the next cut ?
The only + side to not having more than 3 days slurry storage, is that we don't have any to put out, and the huge yields mean we aren't using any aftercut fert this year, and most of the ground will be grazed, not much more silage to do at all this year, 25 acres haylage ready next week, 40 acres silage late september, and anything too far ahead of the cows.