Gardening for fruit for veges

I've always had a hard time growing fruit or veges.
What I grow is nothing like what farmers grow.

Asked a few different people 'how do farmers do it.?"

Got a repeated reply.
'At specific times, they hire an expert fertiliser expert. He comes in and tests the soil, sees what is growing, the stage of growth and recommends what amount of fertiliser to add and when.'

ok, so how do I do that?