Its super easy to just mix up some of your own soil. Get a 5 gallon bucket, or a bigger trash can if you need more.
Just use Subs mix for a guide, you can mix as little or as much as needed. And seriously its gonna work out good for you. I dont think Iv ever read a complaint about it.
Subcool's Super Mix
The mix is placed in the bottom ¼ to ½ of the container and blended with base soil. This allows the plants to grow into the strongly concentrated soil and, in the right size container, they need nothing else but water throughout the full growing cycle. With strains requiring high levels of nutrients like Cheese and Space Queen and other high energy demand strains, we go as strong as ¾ of the container with Super Soil but this is only with a small percentage of strains.
Here are the amounts we have found that produce the best tasting buds and strongest medicines:
*** If using an RO system add in 1/2 cup powdered Cal/mag
8 large bags of high quality organic potting soil with coco and Mycorrhizae
25-50 lbs. of organic worm castings
5 lbs. of Blood meal 12-0-0
5 lbs. Bat guano 0-5-0
5 lbs. Fish Bone Meal 3-16-0
¾ cup Epsom salt
1 cup Sweet lime (Dolomite)
½ cup Azomite ( Trace element)
2 Tbs. powdered Humic acid
1/2 Batch:
4 bags Organic Base Soil
12.5-25 lbs. Worm Castings
2.5 lbs Fish Bone Meal
2.5 lbs Bat Guano
2.5 lbs Blood Meal
3/8 cup (1/4 cup + 1/8 cup) Epsom Salts
1/2 cup Sweet (dolomite) Lime
1/4 cup Azomite
1 Tbs Powdered Humic Acid
1/3 Batch:
2.7 bags Organic Base Soil
8-16 lbs Worm Castings
1.7 lbs Fish Bone Meal
1.7 lbs Bat Guano
1.7 lbs Blood Meal
1/4 cup Epsom Salts
1/3 cup Sweet (dolomite) Lime
2.5 Tbs Azomite
2 tsp. powdered Humic Acid