I used some of my precious compost at the bottom of the trench and added some pure horse manure given to me by a neighbour. The manure will be too strong for plants but their roots should take a while to get down there so they should all right.
Now all the strawberry patch has a good layer of compost under it as I did the same last year for the other half of the patch and got a better crop off that half.
My patch is a 4ft. wide by 12ft. long strip. I plan to have three rows down the patch but will plant only two rows with each plant a foot apart but leave space on one side for planting runners next year.
The plants I have in already are already in three rows and will need renew one row next year with plants from runners. However, I took the opportunity to cut off the old leaves which then enabled me to weed between the plants and remove the rogue runners.