Well for this mix ratio a "Part" can be whatever volume size you choose.
From a cup to a gallon, or the size bag you bought it in.
When I went to the store I grabbed:
2 Bonemeals
1 Bloodmeal
1 Kelp meal
And I got two kinds of Guano, one high in P the other high in N.
Now when you read the directions on the amendments you buy you will see that they recommend 1 to 2 tbs per gallon of soil for most amendments. And 2 to 4 tbs per gallon of soil for Bonemeal.
See you need about double the amount of bonemeal.
So if you were gonna make a small mix you would take say:
4 tbs Bonemeal
2 tbs Bloodmeal
2 tbs Kelpmeal
2 tbs Guanos (one tbs of each type)
2 tbs dolomite lime
That comes to 3/4 of a cup of organic mix for 1 gallon of soil.
Or you can mix the whole batch up together
And measure out how much you need for say 5 gallons of soil.
Thats 5 times the amount for 1 gallon, So..
20 tbs bonemeal works out to: 1 cup and 1/4 cup
10 tbs bloomeal is : 1/2c and 1/8th cup
Kelpmeal 1/2c and 1/8th cup
Guano : 1/2c and 1/8th cup
Lime: 1/2 c and 1/8th cup
Total:
3 and 3/4 cup of mix per 5 gallons of soil
This is shooting for the Hot side for an outdoor grow at max Potential.
If you are doing inside you may need only half strength portioned out @ 1 tbs instead of 2tbs per gallon soil of stuff like guano... That would make the total for 5 gallons of soil just under 2 cups of Mix
Iam an outdoor grower who uses the native soil at the site. I just dig up a hole and put that dirt on a tarp. Then throw on a few cups of mix depending on how big of a hole I dug / want. Mix up the dirt and put it back in the hole. Then Iam done with nutes untill flower time where I can water with a Flowering tea.