if im planting outside in the ground i cant really afford to give 38 plants 20 litres of potting soil each, could i use 600 litres of peat and 100 litres of fetilizer compost, i heard peats meant to be a decent medium with fertz?
peat has a tendecy of becoming acidic over time, why not get some perlite and vermilite to mix in. Also, yo can add in a little sand for filler. Just remember the less soil the more nutes you will be required to use.