Field lab - Composts
The range of composts available to organic growers is limited, and for propagation of seeds many growers are still using peat based composts for its blocking ability and reliability. Over the 2012 season many growers have been trialling different composts including an industry led trial with a biochar/coir compost manufactured by Carbon Gold. Biochar is a form of charcoal that is used to improve soil fertility. It is made by heating biomass while restricting the oxygen supply.
Most organic growers would rather not use peat composts. There is also increasing interest in making your own composts for use in propagation. Biochar is not something that has traditionally been used in composts; but the theory is that as a fine-grained and highly porous form of charcoal it has a microscopic honeycomb-like structure that provides the perfect habitat for beneficial soil microorganisms such as mycorrhizal fungi and actinomycetes bacteria to flourish.
Biochar also acts like a sponge that can improve the water-holding capacity of soil or compost, lessening the risk of drying out; reduce the frequency of irrigation as well as helping to retain mineral nutrients that would otherwise be leached away by rain.
There were a few informal trials done in 2011 followed by wider and more structured trials in 2012 with over 20 organic growers, over a wide range of locations, scale and crops. The trials have mostly been conducted against whatever the growers normally used (often a peat based or coir based compost) though some growers were trialling it against home-made composts. We held a field lab event at Hankham Organics on 25 August, and had a follow up meeting on 10 November.
To attend this meeting, please contact us on firstname.lastname@example.org or call us on 0117 914 2400.
Hankham Organics is a vegetable box scheme based in East Sussex. They are fortunate to be working with wonderful soil and growing in a spectacular glasshouse. They have developed a unique growing system and are constantly trying out new ideas; some more successful than others. To keep food miles to a minimum they only deliver between Brighton and Hastings.
Objectives of the trial
- To investigate the role of biochar as a nutrient extender and water conservator in propagation composts.
- Adding biochar to existing compost
- Using Carbon Gold seed and/or potting compost
Hankham Organics have been asked to keep the following records:
- % Germination for each variety in each compost
- Record of visual appearance - size/vigour, health, pest/disease damage, deaths, colour. As a minimum this should be recorded at time of planting, but the more information you can record the better.
- Watering - we are keen to assess how the presence of biochar in compost affects watering, so we are also interested in any information on frequency of watering compared to normal compost, or ability to cope in very hot conditions.
- Effect on long term growth of crop. Hankham Organics were asked to plant each sample in a discreet area that allowed them to assess whether the addition of Biochar in the propagation compost affects subsequent growth and yield. It is hoped that they will be able to weigh yields separately, though we understand that this is sometimes difficult to fit around harvesting schedules. In this case, a general assessment will be sufficient.