Potting mix shootout final results
Last week we took the final measurements for the parsley plants we used for our potting mix trials at NMIT Fairfield (see this link for the start of the potting mix trials http://aggregata.blogspot.com.au/2013/08/week-1-of-potting-mix-shootout.html) . Again I will say that this trial is not strictly a proper scientific experiment as there were several variables that would bias the results slightly one way or the other. That said, the trial did provide some very interesting results. Probably the most shocking result was that of the really cheap potting mixes which didn't contain any fertilizers, wetting agents or water crystals. The results were shocking for these potting mixes because the plants involved only grew a tiny amount (some even got smaller) and the plants also showed signs of nutrient deficiency (in the form of yellowing leaves). Another interesting fact that emerged from the trials was that even those bottom of the barrel potting mixes performed o.k if fertilizer was added so if you add your own fertilizer you could actually get some proper growth out of the cheap stuff.
My personal pick of the bunch for these potting mixes was the Miracle Gro multipurpose potting mix. It was fairly cheap at $6.97 and as a control (without adding any extra fertilizer) it outperformed all the other products.
The final results are below, remember each plant started at roughly 45mm in height.
Results summary for all the potting mixes
1. Hortico all purpose blend
Price: $6.30c
Description on packet: For a wide variety of indoor and outdoor plants. Composted pine bark. AS3743
compliant. Contains minerals and fertilizer. Living organisms.
Final measurements
Height with added nutricote fertilizer: 85mm
Height with added osmocote fertlizer: 160mm
Height with added green jacket fertilizer: 90mm
Height with no added extra fertilizers: 65mm
2. Scotts Osmocote multi purpose
Price: $7.98c
Description on packet: 4 months osmocote. AS3743 compliant. Wetting agent, composted pine bark, living organisms. For a wide variety of plants.
Final measurements
Height with added nutricote fertilizer: 65mm
Height with added osmocote fertlizer: 105mm
Height with added green jacket fertilizer: 75mm
Height with no added extra fertilizers: 60mm
3. Scotts Osmocote premium
Price: $10.97c
Description on packet: 6 months osmocote. AS3743 compliant. Composted pine bark, water crystals, coir, wetting agent, living organisms. For a wide variety of plants
Final measurements
Height with added nutricote fertilizer: 130mm
Height with added osmocote fertlizer: 150mm
Height with added green jacket fertilizer: 160mm
Height with no added extra fertilizers: 130mm
4. Miracle gro multi purpose
Price: $6.97c
Description on packet: Controlled release fertilizer. AS3743 compliant. Composted pine bark, wetting agent, living organisms. For a wide variety of plants.
Final measurements
Height with added nutricote fertilizer: 140mm
Height with added osmocote fertlizer: 130mm
Height with added green jacket fertilizer: 170mm
Height with no added extra fertilizers: 145mm
5. Debco potmate
Price: $10.47c
Description on packet: Controlled release fertilizer. AS3743 compliant. Composted pine bark, living organisms, wetting agent. For a wide variety of plants.
Final measurements
Height with added nutricote fertilizer: 90mm
Height with added osmocote fertlizer: 115mm
Height with added green jacket fertilizer: 120mm
Height with no added extra fertilizers: 95mm
6. Debco organic
Price: $13.98
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.
Final measurements
Height with added nutricote fertilizer: 110mm
Height with added osmocote fertlizer: 120mm
Height with added green jacket fertilizer: 110mm
Height with no added extra fertilizers: 90mm
7. Rich gro all purpose
Price: $3.78c
Description on packet: Composted pine bark, living organisms, mineral fertilizer. For pots and all plant types. No AS3743 compliance logo.
Final measurements
Height with added nutricote fertilizer: 90mm
Height with added osmocote fertlizer: 120mm
Height with added green jacket fertilizer: 120mm
Height with no added extra fertilizers: 30mm
8. Miracle gro organic choice
Price: $9.42c
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.
Final measurements
Height with added nutricote fertilizer: 90mm
Height with added osmocote fertlizer: 130mm
Height with added green jacket fertilizer: 125mm
Height with no added extra fertilizers: 45mm
9. Scotts Osmocote plus organics
Price: $11.98c
Description on packet: Composted pine bark, AS3743 compliant, composted manure, blood and bone, seaweed, fish meal, gypsum, wetting agent.
Final measurements
Height with added nutricote fertilizer: 110mm
Height with added osmocote fertlizer: 160mm
Height with added green jacket fertilizer: 170mm
Height with no added extra fertilizers: 120mm
10. NMIT Debco pro
Price: ???
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.
Final measurements
Height with added nutricote fertilizer: 80mm
Height with added osmocote fertlizer: 95mm
Height with added green jacket fertilizer: 80mm
Height with no added extra fertilizers: 50mm
The plants as they were at the end of the trial. Notice the poor specimens in the centre (they are the ones that were potted up in the cheap potting mixes with no added fertilizers).
