Start date 16/11/21

The second soil trial is now underway. Whilst the first soil trial fizzed out due to, largely, a lack of planning on how to deal with fertilising, there were still significant learnings from it. The only soil that coped without any additonal fertiliser was the BioGro Premium Wicking Mix and that isn’t surprising as it contains slow release fertiliser! All the others ran out of nutrients for the plants. The 66% compost blend didn’t drain very well and the soil began to smell.

This trial has been designed to include fertilisers, enabling me to assess both the soil types and the fertilisers. All up there are 12 combinations, this time with no replicates. The idea behind this trial is to use soils that are commercially available and not modify them with additional compost/coir etc. Jeffries Veggie and Garden Soil is widely available from landscape suppliers and also in bagged form. Tuff and Sons (cnr Richmond rd and South Rd) sell a pre-mixed vegie soil which is roughly 1:1 sandy loam:compost. Most landscape suppliers can mix these 2 products together for you so that you only have to add it to your wicking bed. I’ve also added a single planter of the BioGro Premium Wicking Mix since it did so well in the last trial and 1 planter with a product called ‘Organic Loam’ from Woodside Landscape Supplies which is a blend of loam and compost and I suspect will be too heavy and not drain sufficiently but it’s a pre-mixed soil so I thought I’d chuck it in and see.

The sandy loam/compost blend is heavy compared to the ‘potting mix’ style mixes of Jeffries and BioGro. Perlite is often added to potting mixes to open up the soil structure and ensure the mix holds plenty of oxygen for the roots to breathe. So I’ve added in 2 planters where 10% perlite by volume has been added to the heavy soil blend to see what effect this has.



Fertilisers

1 – CulChar by Jeffries. From the Jeffries website (https://jeffries.com.au/home-gardening/jeffries-culchar/) – “Jeffries CulChar is a NASAA organic certified, carbon-rich fertiliser with added BioChar. It has the capacity to hold nutrients, improve soil structure, store soil moisture and support beneficial soil organisms. There is simply no better way to improve the vitality of your soil than with these unique, all-in-one, easy to apply pellets.”

2 – BioCharged Compost by Jeffries. This is not available and is still in the testing phase. It’s an activated form of BioChar and is used much the same way as regular compost ie. mixed through the soil prior to planting. I’ll be top dressing with this throughout the trial to enable comparison.

3 – Rooster Booster by Neutrog. There are a few pelletised chicken manure based products on the market, I tend to use this one.

4 – Dirt Larv Insect Frass by Mobius Farms. This is new to me, whilst I’ve heard of insect frass as a fertiliser, this is the first time I have used it. From their website (link) – “Mobius Farms is an innovative enterprise turning food waste into value! Using insect bioconversion technologies, we produce high quality insect protein-based products suitable for the pet, aquaculture and livestock markets. We do this by collecting food waste from commercial kitchens, restaurants and caterers and feeding it to a fabulous insect called, the Black Soldier Fly Larvae. This little grub is a voracious eater with an appetite for almost any foodstuff! From bread to brewery mash, pickles to potatoes, oranges to offal; there’s not too much they won’t eat. Within a matter of two weeks, the larvae grow from miniscule to harvest ready. Each kilogram of larvae consumes up to four kilograms of organic food waste in its short lifetime. They are able to be reared intensively in a small footprint of land with very minimal water consumption making them a sustainable source of insect protein. ​The frass (manure) by-product is collected, composted and recycled to local community gardens and growers who produce food for our restaurants, closing the loop on waste. Mobius Farms is the circular economy in action.”

I’ll be growing 1 x Tommy Toe cherry tomato* in each WaterUps® Square Planter and using the brand spanking new WaterUps® Tall Square Planter Garden Frame designed and manufactured in Australia by Flexi Garden Frames (https://flexigardenframes.com.au/). Each tomato will be pruned to a single stem and grown up a cloth twine secured to the central hub at the top of the flexi garden frame and tied to the tomato stem below the lowest leaf. You’ll notice in the picture below that there are holes in the frames which enable cloth thread or wire to form a cage around the plants or to secure a climbing plant to them. In this trial I won’t be using these holes but I have planted 2 WaterUps® Square Planters in the main vegie patch and will be letting the tomatoes grow wild so will be supporting them using these holes. Check our Facebook/Instagram for more information.

* The BioGro and Organic Loam soils were last minute additions to the trial. I didn’t have any more Tommy Toe cherry tomato seedlings so they have different cherry tomato varieties (BioGro – black cherry, Organic Loam – orange cherry).

Day 1 setup of soil trial

The cloth tie is secured through the central hub to provide support for the tomato to climb.

All plants will be pruned to a single stem to allow comparison.

The greenhouse showing shade structure.

Trial Design

SoilFertiliser
1Tuff & Sons Vegie MixCulchar
2Tuff & Sons Vegie MixBioCharged Compost
3Tuff & Sons Vegie MixRooster Booster
4Tuff & Sons Vegie MixInsect Frass
5Tuff & Sons Vegie Mix + 10% v/v perliteCulchar
6Tuff & Sons Vegie Mix + 10% v/v perliteRooster Booster
7Jeffries Veggie and Garden MixCulchar
8Jeffries Veggie and Garden MixBioCharged Compost
9Jeffries Veggie and Garden MixRooster Booster
10Jeffries Veggie and Garden MixInsect Frass
11BioGro Premium Wicking MixCulchar
12Organic Loam (WLS)Culchar
Soil and fertiliser combinations in the soil trial

The trial is inside a large greenhouse which has a shading structure to keep it cool, 6 roof vents and a misting system. The temperature and humidity will fluctuate inside the greenhouse but the extremes will be much less than outside. Day time temperatures will be cooler, night time temperatures will be warmer. Importantly, the humidity inside the greenhouse is much higher which causes less stress on the plants during hotter weather. A misting system can be switched on regularly to keep the humidity up. The increased humidity does have it’s issues with fungal problems more likely. The tomato seedlings were dusted with a sulfur/copper product prior to planting in the soil trial to help prevent fungal issues and this will be monitored throughout the trial.

Soil pH was tested prior to the addition of fertilisers using 2 methods. The first used a Brunnings three-way meter (moisture/light/pH) and the second used the Manutec kit designed by CSIRO. I’ve been curious but skeptical of these cheap meters, particularly those that can measure multiples variables so I bought one for $15 from Bunnings.

SoilpH (Brunnings meter)pH (Manutec kit)
Tuff & Sons Vegie Mix6.58.0
Jeffries Veggie and Garden Mix6.57.5
BioGro Premium Wicking Mix6.56.5
Organic Loam (WLS)7.08.0
Soil pH results

Testing soil pH can be tricky, particularly with potting mix styles due to the coarseness of the media. Typically, lab soil pH tests involve drying the soil followed by sieving it. If time permits, I’ll repeat the Manutec test on dried, sieved soil samples.

As the table shows, the results differ significantly between the tests other than for the BioGro mix. Given I’m not going to adjust the soil pH the results are what they are. If the Manutec results for the Tuff and Sons and Organic Loam are correct, you would expect to see the tomatoes struggle as this high soil pH will lock out nutrients from the plants.

Fertiliser Application rates

The surface area of the soil in a WaterUps® Square Planters is ~0.2m2. This was used to calculate the fertiliser application rates as per the manufacturers recommendations.

Culchar, Rooster Booster and the Insect Frass were added at a rate of 100g/m2 (ie. 20g per planter). BioCharged compost was added at the rate of 2L/m2, 0.4L per planter). The fertilisers were added over the soil in a roughly even rate and then mixed through the soil with a small garden fork which was rinsed with water between planters. Additional fertiliser will be added every 6 weeks during the growing season, spread evenly over the soil surface and watered in. No mulch will be added.

If you’ve been following some of the trials WaterUps are doing (https://www.waterups.com.au/news/) you will have been very interested to read the latest blog on rates of water usage in a Square Planter. With 2 tomatoes per planter, Eric Sturman noted that at the end of October the plants were 1.2m tall with more than 30 fruit per plant and the water reservoir had dropped by 2/3rds in only 7 days. This matches my observations that water hungry plants at the peak of their growth can use huge amounts of water and that the ‘3-4 weeks between’ watering that we state for the WaterUps system does come with a few caveats. Between April and September/October, given an average rainfall for my area, I don’t need to fill the WaterUps reservoirs at all but January/February it’s often 1-2 weeks. The take home message is to keep an eye on the water levels and the easiest way to do so is by making yourself a ‘dipstick’ which could be as simple as a wooden handled rake. Stick this down the reservoir pipe when it’s full and mark the full line. I personally have a 15mm thick piece of dowel which lives in the vegie patch to be able to check water levels.

The reservoirs of the Square Planters in the trial were filled on Day 1 and will be monitored throughout the trial. They will all be filled on the same day to keep things simple but I will be taking note of the levels of each bed.