How does your garden grow?
SoilFixer sunflowers shine a light on the best soil additives mixes.
We planted our sunflowers (Russian Giant) into the test beds very late this year, in early August, after the Charlotte potatoes came out. The thinking was simple; sunflowers need lots of water and nutrients and they will really test the different soil additive mixes.
One clayey soil (control), clay plus our super soil additive (code named SF60), clay soil plus compost from our HOTBIN® (ie high colloidal humus compost), clay soil plus raw biochar, clay soil plus ‘shop’ bought compost.
The SF60 formulation has resulted in 2.7m high Sunflowers and the earliest flower heads. They are 32% taller than average over all beds.
The Biochar are only 1.6m, the compost from our HOTBIN® and shop compost are near equal at 1.8 and 1.9m. The control is interesting; it is currently 2.2m – but!
The clay control has a fascinating story. A few weeks back, I noticed the soil height in all the tests beds had dropped some 10cm below the top rail. Basically the soil had compressed since filling for first time back in September last year. Decision taken to top-up at end of season with like-for like mixes. Then my neighbour tore up a path of garden to make a new patio, and offered me one tonne of soil.
I wheel-barrowed it all back. I was running out of a space to store it. I thought well it’s same clay soil as the control – it won’t affect things if I add the extra soil in to one bin now. How wrong was that!
At the time of addition (four weeks ago) the clay soil sunflowers were second to last place.
But four weeks later, one week of heavy rain and two weeks of fantastic late summer sunshine and bang – they caught up the best performer. I’m pretty sure this is all down to water. The extra clay not only holds water; it has stopped the layer below drying out as fast – they had more water than other tests beds.
So this brings us back to the test.
The sunflowers tests indicate water retention within the soil additive as one of the most critical features, especially when looking at flowers in the late summer months.
Those who have read up on biochar as a soil additive will be asking – but surely biochar holds water. Why did the Sunflowers in biochar do poorly? Surely compost also holds water?
All these are true – the key question is “how much water (water holding capacity) and for and for how long (water retention time)”.
Consider this table of soil raw material properties:
Compost and biochar improve poor soils. Colloidal humus retains a lot more water. Just as importantly it holds onto to it for far longer. Compost dries at 100C in about two hours. A similar size colloidal humus sample would only be dry after 8-10 hours – it just doesn’t let go!
Not sure? You can try for yourself by taking 100g samples of BBQ charcoal, compost, clay soil. Wet them, roll into a ball in palm and leave them out in sun. Every hour check to see if they fall apart or are still pliable. The alternative is to use the kitchen oven to dry – but best check first. We might know all germs are killed within minutes at 100C, it still doesn’t mean the cook will be happy.
Colloidal humus is remarkable stuff. Even small amounts have a profound impact on soil. So why not just add loads of colloidal humus to the soil. Well you need balance. Pure Humus is a sticky mass full of water. It does not let the soil breath (roots need oxygen). In essence, soil needs more colloidal humus, but not too much!
What we are attempting to create with SF60 is the world’s best, (completely natural and sustainable) soil additive. OK we know that’s a huge goal for a small team, but we are very close. Want to test for yourself? Well, SF60 is like gold dust as we are still making it in our test facility. But we are keen to get testers who blog involved so please contact firstname.lastname@example.org.
PS: want to know how not to grow tall sunflowers? Plant seeds direct into poor clay soil, next to shed (shaded for part day and protected from rainfall. Leave them to fend for themselves and compete with weeds. Do not provide extra water. The seeds we planted have been in twice as long as those in test beds (16 weeks versus eight weeks). They are pathetic weaklings at 0.3m height and no signs of flowers. That’s a huge eight fold smaller. Nature has such huge capacity to change plant growth!