Question
I have a very large oak tree in my garden (175 years old) which saps the goodness from the lawn and the planting area. At the moment the lawn area around the tree is like a dust bath and I can't afford to purchase fertilisers which, because of the size of my garden would cost me too much money.  I wondered if there is something inexpensive that would be effective or one I can make myself?

Answer
The tree does not spa goodness for the lawn. The tree compete with nutrients, water and sunshine and the tree wins. Also the soil around the tree is compact due to root action near the surface and that will prevet grass from growing.

You can buy inexpensive 10-10-10 fertilizer, or even urea 40-0-0 and use that. You do not need specific lawn fertilizer. However, the competition from the tree in terms of sun, water and soil compaction is greather than fertilizer.

You should not expect to grow grass under mature trees.