A month ago a sowed a new lawn using a 50:50 perennial ryegrass/fescue mix.
It has come up well, although variable. The last two weeks have been very
wet indeed. At the weekend I was able to mow most of it to 50mm.

However there is a large contiguous area which has stunted weak grass with
die-back of the tips. The blades of grass are green at the base, turn
suddenly yellow about half way up, and are brown and shrivelled at the tips.
Because it was an autumn sowing, I did not apply fertiliser before sowing.
The soil is alkaline recently tilled clay with a pH of 7.5 or more.

I suspect there is a nitrogen deficiency and am wondering if the new grass
would tolerate fertiliser and whether applying a nitrogenous fertiliser may
cause sappy growth and problems in the winter.

I would be grateful for your thoughts.

cheers, Davy