Have had  several large areas of grass laid about 4 weeks ago

mostly looking lush apart from a few trouble spots

its time for a feed, what easy to apply products do people use, bearing in mind its quite a large area, total 700 Sq M.

Thanks.

Outside of plenty of water, a light spread of nitrogen fertilizer every few months (3 for me) should be all you need.

Just mix a bottle of Sangsom with water and sprinkle all over a few days later it will come up half cut ✂️ 

Vegans

Do not use too much fertilizer on fresh grass . Water is the best it needs and best a few times a day , it does got sun , together with water and halfway decent soil and it will be fine . After a while , Nitrogen fertilizer can be used , but you can also use some of the black soil they sell , sprinkled across the top . It is rich in nutrients and won't burn your grass .

Forgot to mention... If you didn't put down a couple cm of sand before laying the sod, put some on top of the "trouble spots".  Or, lift up the sod, add sand, and re-lay.

Thanks for all the tips

it seems that now we have a grub infestation thats eating the roots and causing a lot of very semi dead looking areas, ill have to fix that first before fertilising  and / or black soil

any recommendations for a high nitrogen fertiliser, bearing in mind there is 700 odd SQ Metres to do