Basil and radish plant growth results (Jason Daff, spring 2017)
Jason Daff (one of our testing community) set up trials using Levington’s F2 commercial growing media as the control. He added 10% and 20% SF60 with the F2. A fourth set of seeds were grown with F2 topped up with a commercial slow release fertiliser (Osmocote).
- Basil in F2 + 20% SF60 showed a 10% biomass increase over the F2 control
- Radishes in F2+20% SF60 were 5% decrease in biomass compared to the control.
see photos below
Why one positive and one negative result?
Looking at the basil – although not as positive as the basil grown in Tony’s kitchen trial – it's still a healthy 10% increase. Why is the growth difference lower?
Jason’s testing used professional equipment and highly-controlled conditions. Variables such as the intensity of light, number of light and dark hours, water and temperature were all controlled. This test is looking more at the impact of nutrient supply. This is very different to the other tests reported. In the raised beds and pot tests each has a watering regime that creates high and low water content. We are finding water (and enhanced use of it) is a major plus point for the biochar-colloidal humus SF60 system. In these tests, this variable has been removed as the water is constant level via a capillary mat.
Looking at the radish – why are the results negative against the control and negative versus the basil test?
After eliminating possible causes such as pH and physical density of the mixes, we are moving towards the probable cause as nutrient “locking” in the SF60. The radish are growing (adding weight) twice as fast as the basil - potentially they are exposing nutrient issues earlier. Biochar locking nitrogen is known to occur when the biochar has not been fully activated. Of course, our SoilFixer promise is that SF60 is fully activated biochar since it goes through our special composting process. “Locking” is a concern.
Having looked closer look at the production record for this batch of SF60, we might have out-smarted ourselves! We added some fresh biochar at the end of the process to help make sieving large particles coated with sticky colloidal humus easier. We might have solved one issue, but have also added non-activated biochar! We need to await further tests. If this is the case, we will learn from it and adjust production. If true, it re-enforces our belief that simply mixing compost with biochar is not an effective activation process. Our special active composting process would be confirmed!
- It's hard to compare results from trials where SF60 in added to soil with those where SF60 is added to a commercial growing media – starting from different places.
- The % increase in productivity when amending (good) growing media are always going to be less than the % increase when amending a poor soil.
Global Tests results
We're always searching for reports on improving plant growth using biochar and other additives. We'll come back to this figures many times, but the table below presents a snapshot:
|Worst case (negative impact)||Best case (positive impact)||Source ref|
|Biochar||-26%||+39%||S. Jeffrey, meta-analysis of all biochar reports - posted on IBI website|
|SF60||-20%||+200% (x2)||SoilFixer, raised beds|
|NKP fertilisers||n/a||+300%||AHDB fertiliser manual|
|Hydroponic and aquaponic||n/a||+10000 (x10)||S Singh, Hydroponics review (note compared to rural Indian soil farming)|
There are numerous factors that limit plant growth: genetics > uv light > water > oxygen concentration (in soil), CO2 concentration in air and in soil, temperature, macro NKP nutrients, micro trace minerals, soil microbes (symbiotic and or pathogenic), physical texture and structure of the growing medium. A quick comparison of the results against possible limiters informs us there is a lot more to achieving optimal growth than just nutrients.
Indeed in farming, NKP gains are well below the maximum because the economic cost of adding more fertilisers is higher than the value of the crop yield gain. Normally see max of 30% improvement via fertilisers. Hydroponic systems offer big gains over poor soil – the problem is the cost of the equipment. Hydroponics is taking off for growing expensive produce sold into well-off countries. Overall hydroponics is a small activity - it has been estimated that over 95% of all agriculture and horticulture happens in soil. Improving soils by 10-20% is a massive win.