Im back! With the beginning of August we begin our countdown to Spring, although you wouldn't be the first to wonder whether or not Spring had already arrived! Across our suburbs cherries and other fruits are blossoming, and a few of my potted plants are showing the first signs of life!
I will leave our unseasonable warmth for another post, for all winter I have been thinking upon more and more upon another pressing issue... Soil mixes.
Much of last year, I spent my time searching for the best soil medium that would grow a wide range of plants, and I could use as a reliable medium that would both retain a good amount of moisture, but also would also be porous enough to allow the plants roots access to plenty of air.
As can be read in my previous post on soils, the role of the soil medium is simply to anchor the plant, provide dissolved nutrients and water, and to provide air.
I began my search on the GardenWeb forums, and pretty soon into the adventure found that a forum member ‘Tapla’ was renowned for having two soil mixes that met all these properties. One of these mixes his ‘5-1-1’ mix was made up of three ingredients; partially composted pine bark fines, perlite and peat moss.
After finding suitable pine bark fines, I quickly potted up a number of plants including fig trees, blueberries, bay tree, dwarf lemon tree and a dwarf peach.
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| All potted in Tapla's 5-1-1 |
I was very excited and expected a tonne of new growth. The season however by this stage was nearly over, having potted everything up in the beginning of February, the final month of summer.
Besides one or two blueberry bushes, I saw very little growth from any of my plants after planting in the mix, despite having a month of summer remaining. I have various possible theories why, in particular some very hot days which might have stressed the plants. I have a suspicion that my figs in particular were heat stressed, because when the heat finally dissipated the figs started to put on some new leaf growth.
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| May 2013 - Where's my growth!? |
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| Feb 2013 |
I had a couple of other issues with the mix, on most days I would water it in the morning, and come home to find plants wilting- despite the soil being obviously damp. A quick drink and plants perked up again. The biggest issue however came when I had some issues with my blueberries suffering a nutrient deficiency and beginning to show signs of leaf chloriosis.
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| Chloriotic Blueberry Leaves due pH |
Blueberries are picky plants in their pH requirements, and despite the 5-1-1 mix being inherently acidic the water I was using was too alkaline, and was slowly killing my plants. I fixed this by adding small amounts of sulphuric acid to the watering can before watering, but in the process also added more soil mix to the plants.
It was during this process that I noticed that the soil mix was absolutely saturated despite not having been watered at all that day. The mix had collapsed to the point of a store bought mix, but seemed to be holding excess water, not the porous aerating soil I hoped for. I amended the mix, adding larger pine bark pieces, and the plants seem to be doing ok, although they are all now dormant.
Unhappy, I decided to follow in the path another forum user had suggested, coconut husk chips (CHCs). CHCs are the fibrous part of the coconut that have been cut into fairly uniform square sizes. The chips come in a compressed block that supposedly expands to make up to about 60L when hydrated. Coconut husk chips have some beneficial properties to pine bark, such as hydrating from a dry state easily, where pine bark fines tend to become hydrophobic once dry. CHCs also held a good amount of air and water.
Using CHCs I have potted up most of my plants, and now only a few plants remain in the original 5-1-1 mix I made in February, despite having not had a chance to see if it is effective or not.
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| My current mix- Primarily coconut husk chips, with perlite and pine bark |
Still, doubts remain. Did I throw the 5-1-1 aside too quickly, and judge it too harshly? If I had potted in Spring would there have been a difference? Will the CHCs even perform well (everything has been potted whilst dormant).
The CHCs certainly look good when mixing, and look like they will perform an excellent job, but even this, perhaps, is unnecessary.
And so, beginning in the Spring of 2013 I intend to test all of this with an experiment.
The Great Container Mix Experiment
Introducing now the great soil mix experiment, where I will attempt to determine for myself once and for all the best mix to put my potted vegies and fruit trees into! Is it really worth all that effort to source fancy ingredients when a $5 bag of potting mix from Bunnings will do the same thing?!
There is only one hopefully, mostly scientific way to determine this. Grow a number of the same plants in different soil mixes and see how they perform under the same conditions. And to be super sure, I will grow a couple of different types of plants side by side.
I am going to grow four types of plants each in three different soil mixes and measure the differences in growth across the season. I am going to record all growth against a control group of plants using straight potting mix from Bunnings. In total, I will have three different mixes to test;
· Pure potting mix
· Tapla’s 5-1-1 mix (two versions)
· My current experimental mix which is made up primarily of CHCs but also has pine bark, perlite, compost and manure
For this experiment I have decided to use four different types of plant so that my results are more than just the result of a particular type of plant preferring a particular mix. The plants I will choose for this are;
· Grape tomato, which does not require staking
· Fatalli Chilli
· Basil (or possibly egglant)
· Banana Chilli
These plants have been chosen for their size and suitability for pots, and also based upon what I use a lot in cooking.
Plants will be grown in two different sized pots. Half will be in smaller 8L pots and the other half in larger 30(ish)L pots. All seeds will be germinated directly in the mix so that transplant shock is not a concern. 3 seeds will be planted in each pot and the most healthy seedling kept.
Plant growth will be measured in a number of ways, including germination time, height and apparent vigour. Fruit count and quality will also be recorded at intervals. Photos will, of course, be provided at weekly intervals.
I am quite excited to get this on the road, and have already mixed up the 5-1-1 mix! Read more in my other post!
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