Even though I have been gardening for a few years now, and I am improving slowly, this year I discovered that my soil is seriously lacking in fertility. Since January, I have been attending Jim Cronin’s ‘Organic Market Gardening’ course in Bridgetown and on day one I got about 1 out of 10 for my soil fertility. However all is not lost and there is much I can do to improve it. This article will give a very brief overview of the vast subject that is soil fertility and soil organisms.
A new generation of soil scientists promise a renewed understanding of soil processes. We now know that we need to be looking at the soil from the following view points:
- Biological – what are soil organisms and how do they help soil fertility?
- Chemical – which elements are necessary for plant health and which may be toxic?
- Physical – how do soil physical properties affect water movement and nutrient uptake through the plant roots?
According to Dr Elaine Ingham, known as a leader in soil microbiology and research of the soil food web, we should be getting away from using fertilisers on our land. It doesn’t matter whether you are gardening in your back yard or on a larger scale of ¼ or ½ acre or even 50k hectares. The future lies in getting away from chemicals and reducing damage to our environment. Growing food for ourselves should not mean we have to destroy our water quality or our land, or our neighbour’s land.
It is possible to return the soil to a condition of health in an holistic way, and that this is not going to cost much or take years to achieve. Believe it or not, experts thinks we can get there within one and four growing seasons! I’m not sure how long it will take in my ‘concrete’ type soil, but I will keep you posted.
In order to improve soil quality you need to understand the organisms (see soil food web picture) that live within it and make sure you have the correct organisms in your soil. If you can reproduce this soil food web in your soil, you will be well on your way to getting rid of disease and pests in your plants and growing more nutritious food. Another consequence of improving the biology in the soil is an increase in yield, if you build the correct soil structure, water and oxygen are absorbed into your soil and are held there, roots will then grow as deep as they possibly can and this will help to enhance the cycle of nutrients.
Picture reproduced with permission from Soil Foodweb NZ
So what does a healthy soil contain? Not just a few earthworms and bacteria! All soil contains bacteria. If you have any kind of plant growth at all on your soil, be it weeds, grass or even poorly growing plants – you have all the bacteria that you need. But if your soil fertility is poor you need to repopulate it with the rest of the organisms from the soil food web.
Just to bamboozle you with figures, a healthy soil will contain anything from 5million to 500million bacteria per TEASPOON of soil and you can even have up to 2 billion in a teaspoon of soil from a forest or a highly productive garden. That teaspoon of soil, in a healthy state, should contain 40 miles of fungal hyphae (strands).
The bacteria and fungi make the enzymes that are harvesting all of the mineral nutrients from your garden by breaking down the soil, sand, clay, pebbles, rocks and organic matter, basically anything available to them. In order to make these mineral nutrients available to your plant roots, you have to have the little guys from the third level of the soil food web, the protozoa, nemotodes and microarthropods to eat the fungi and bacteria, and you need earthworms to eat the bacteria and fungi and the protozoa……you get the picture. You have to have a predator in the system who eats the bacteria and the fungi, that’s when plant available nutrients are released back into the soil at gradual rates that supply plants with a steady diet of nutrients all season. The greater the interaction of decomposers, their predators and predators of those predators, the more tightly nutrients cycle from stable forms in soils to plants, and back again.
Everything is in your soil, regardless of how bad you think your soil is! According to Elaine Ingham, the microorganisms have all the mineral nutrition that they require available to them even on poor land, but they need assistance to start mining it, they have to have an energy source. That’s where roots come in, the plant roots secrete sugars which feed the microorganisms, bacteria and fungi make the enzymes to solubilise any mineral nutrients from the clay, organic matter, rocks and pebbles. All we gardeners have to do is work with the soil we have to get it working for us.
Our land management choices help determine what lives in our soil and how well it works for us. So how do we improve the soil health? Crop rotation, limiting soil disturbance and compaction, adding compost teas, managing the ph level of the soil, cutting out the use of chemical fertilisers and introducing green manures as well as growing cover crops, moving away from monoculture are but a few positive steps we can take…and did I mention Rotation, Rotation, Rotation?
Seed Savers are holding a very interesting Soil Health workshop in June, it will be delivered by Dave Beecher who studied under Elaine. Dave is involved in a 5 year study with the Department of Agriculture whereby the study aims to develop a ‘conventional to biological’ farming transition programme system for a group of sixteen individuals (on farms all over Ireland) who have come together to learn about and carry out the basic principles of biological farming, in an effort to produce food, feed and forages of high nutritional quality. If big farmers realise that they can increase their yields by NOT putting chemical fertilisers on their lands, this can only be good news for all of us. More about this study here – Danu Farming Group: httpss://ec.europa.eu/eip/agriculture/en/find-connect/projects/dan%C3%BA-farming-group-project-plan-biological-farming
Learn a bit more about soil ecology & soil food web www.ecoversity.org/archives/soil_ecology.pdf
Dr Elaine Ingham’s website: www.soilfoodweb.com
I hope this article has given you a bit of an appetite to learn more about the organisms in your soil. In an effort to boost my own soil health, I intend to grow more green manures and ground cover crops this year instead of covering beds with black plastic In order to fast forward and get a bed ready for my winter 2018 garlics, I’m trying Jim Cronin’s suggestion of growing three green manures one after the other(phacelia, mustard and alfalfa) which will be rolled and mulched back into the ground before they flower, in order to give us a bumper crop of garlics for 2019…..watch this space! Interested in improving your soil health? Why not attend our Soil Health workshop on Sunday 24th June. Click HERE for full details and booking.