Kelp is a fantastic addition to any soil mix, and we use it in varying quantities in all OHP soils.
Use 1-4 tablespoons per gallon of soil, or use as a topdressing - simply mix into the top 1-2" of soil and water the soil surface to spread the effects.
1oz packet = 2 TB
8oz bag = one cup
16oz bag = two cups
Bags and pouches are home compostable :)
