Soil amendment products ?

I need to cover about 800 sq ft of sod but need to rototill the are first. Before I do this, I understand that I should add a soil amendment. So my question: Are there any good soil amendment products that I can just hook up to my garden hose, to spray the area I want to lay sod on? This would seem to be a much faster and less expensive solution than to buy compost products that come in bags. Also, can this product be found in store like Home Depot or Orchard?