I agree with all the above compost tea mulch etc. Did you put in some mycorrhizal fungi when you planted it? If not there is a product called Q4 you can add after which although not adding at the time of planting is better than not at all.
Go get your self some liquid seaweed personally I find maxicrop the best though vitax is good too and probably made in the same place. Make sure you water it regularly with that during this first season especially so if it end up being a dry one. Yew is resistant to almost all conditions and issues once established
but it can die in its first season if you don't water it properly.
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The best feed to make yew grow along with the seaweed to help it establish is bat guano. It's certainly not the cheapest feed but it really gets it growing and I have established quite a few yew hedges for people by now. I used the brand below establishing some yews the last few years and nothing has made it grow faster than that:
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