If you are planting in previously undisturbed cow pasture, you should be fine & your trees should live long and prosper. However, if the soil has been disturbed and compacted due to construction it would be best to add organic matter and a soil inoculant such as ICT Organic 1-2-3 Tree.
This will help rebuild the microbial life in the soil which will improve soil structure, nutrient cycling and plant vigor.
The nation that destroys its soil destroys itself.
Franklin D. Roosevelt