Best things and amounts to mix into soil for the garden
With 7 cu. yds. of soil you must be building a bunch of large raised beds. If you are purchasing a commercial mix of soil for a raised bed you should not have to add anything, depending on the composition of the soil you purchase. Make sure you are not getting ‘Potting Soil”, potting soil is not what you want for a raised bed. The “50/50 blend” does not provide enough information to make a recommendation on additives. The place where you purchase the soil should provide a breakdown of what they have put in the mix. You “may” have to use fertilizer in your new beds. The amount and kind of fertilizer will depend on exactly what you are planting. As an example, if you are planting carrots, beans, radishes, or beets they do not want much nitrogen, whereas some other plants like lettuce do. After the first year of using your raised beds, as part of your Fall cleanup, you can work some compost into your beds. The compost can be some that you have made, or compost from the Public Recycle Center, or from a local vendor. Thanks for sending this question to ‘Ask and Expert”. Here is the link to an excellent Oregon State University publication in Home Gardening. There is a chart in this publication that has planting dates for all kinds of vegetables, as well as other valuable information on home gardening.