While we’re on this topic of nitrogen tie up……..Here’s something else that should likely be considered……..I think you have a window of time after the summer vegetation has been put to the ground that is optimal for getting your seed up and growing before this N tie up occurs…….After the summer “hay” has been on the ground for a couple weeks or so then it enters a phase of really sucking N where its not a good environment to establish new seedlings in…….I went back and spread a little more rye around the outside perimeter of the field a couple weeks after everything initially came up and I didn’t see anywhere near the establishment and jump for that seeding as my initial one. I think you need to put your seed out at the same time you put the hay to ground and then wait to do any other top sowing until after this decomposition drag has passed. It may sound a little funny but its like anything else in nature and there is a certain time when things are ripe to sow your seed and times when it aint.