As part of my studies I have recently starting testing different commercially available potting mixes. Although the test I have performed isn't strictly scientific it should give a good indication of the effectiveness of different brands. I chose curly leaf parsley as the plant to grow and planted it out in 100mm black plastic pots. The pots are all placed in the same area in the outside growing area of Fairfield TAFE. I have also used 3 different types of fertilizer (Nutricote Exotic, Osmocote Exotic & Green Jacket Exotic) in conjunction with a control (no fertilizer). The prices of the different potting mixes vary considerably and many seem to contain the same ingredients. Some of the mixes display the logo which indicates compliance with the AS3743 Australian standard and others do not. Strangely the most expensive potting mix does not have the AS3743 logo on it and I think that may have something to do with the fact that it is an 'organic' mix. I'm guessing this has something to do with the natural variance of organic materials. I planted out the parsley into all mixes and also fertilized each mix with the three different fertilizers mentioned above. On planting the seedlings were all healthy and were roughly 45mm tall. I will post the end results once the trial is over.
1. Hortico all purpose blend
Description on packet: For a wide variety of indoor and outdoor plants. Composted pine bark. AS3743 compliant. Contains minerals and fertilizer. Living organisms
2. Osmocote multi purpose
Description on packet: 4 months osmocote. AS3743 compliant. Wetting agent, composted pine bark, living organisms. For a wide variety of plants.
3. Osmocote premium
Description on packet: 6 months osmocote. AS3743 compliant. Composted pine bark, water crystals, coir, wetting agent, living organisms. For a wide variety of plants
4. Miracle gro multi purpose
Description on packet: Controlled release fertilizer. AS3743 compliant. Composted pine bark, wetting agent, living organisms. For a wide variety of plants.
5. Debco potmate
Description on packet: Controlled release fertilizer. AS3743 compliant. Composted pine bark, living organisms, wetting agent. For a wide variety of plants.
6. Debco organic
Description on packet: Superior composted pine bark, premium blood and bone, organic carbon, NASAA input for organic production, no household green waste, ph balanced. For a wide variety of plants. No AS3743 compliance logo.
7. Rich gro all purpose
Description on packet: Composted pine bark, living organisms, mineral fertilizer. For pots and all plant types. No AS3743 compliance logo.
8. Miracle gro organic choice
Description on packet: Composted pine bark, blood and bone, fish meal, seaweed, chicken manure, feather meal, bio stimulants, living organisms, feeds for 3 months. No AS3743 compliance logo.
9. Osmocote plus organics
Description on packet: Composted pine bark, AS3743 compliant, composted manure, blood and bone, seaweed, fish meal, gypsum, wetting agent.
10. NMIT Debco pro
Description: This is the potting mix that NMIT TAFE buys directly from Debco by the cubic metre. I don't know much about what is in it and can only guess as the the ingredients from visual inspection. It looked to contain no control release fertilizer or water crystals. Like all the others it is made from composted pine bark.