Below is an edited interview I conducted with the wonderful Marilyn and Chris, a wicked wife and husband team and co-founders of the Hummingbird Project. They are traveling around the world working with small farms and communities spreading clever permacultural techniques and teaching about the wonders of the Soil Food Web.
Katie: Thank you very much Chris and Marilyn for agreeing to do this interview on the Soil Food Web and everything that you’ve been doing here at Navdanya.
Katie: Could you please explain what the Soil Food Web is?
Marilyn: Sure, the Soil Food Web (SFW) is a way of describing all of the microorganisms that are working together in the soil to help feed the plants. There are several different trophic levels. Trophic is a Greek word meaning food. So there’ll are based on different foods categories that microorganisms eat.
Source: Dr Elaine Ingham’s website http://www.soilfoodweb.com/sfi_approach1.html
The first trophic level includes all plants that are able to photosynthesise, capturing sunlight energy through speasalised chloroplasts, that transfer the sunlight energy in to sugars. The sugars in turn are translocated into the root system to help feed the microorganisms and help set up this whole soil food web.
Katie: Can you tell us why the soil food web is important?
Marilyn: The SFW is important because the microorganisms feed plants whilst plants are also feeding the microorganisms. It’s a series of mutualistic relationships that have developed over millions of years where microorganisms provide all of the nutrients that plants need.
Chris: It’s important for the same reason that the water cycle is important, or the life cycle is important, because without it there would be no terrestrial life of plants on earth.
Marilyn: A lot of people have a misconception that plants need us to go to the store to buy specialized fertilizer and plant food, but it’s completely inaccurate. The plants and microorganisms have evolved over time so they absolutely do not need human beings to add inorganic, synthetic fertilizers to the soil to feed plants. The microorganisms do all of the nutrient cycling, and more importantly make the nutrients bio-available, which means that nutrients are in a form that’s easily absorbed at the root hairs.
Katie: Can you explain just a few examples of these beneficial relationships between microorganisms and plants?
Marilyn: Sure. One of our favorite types that we’ve been talking about here at Navdanya are leguminous plants. These are plants that are able to capture atmospheric nitrogen and convert into a form that is bio-available to plants. Here at Navdanya they’re growing a lot of soy beans for example. Soy beans have a symbiotic relationship with rhybozium bacteria. The bacteria infect the soy beans at the point of the roothair and they physically capture atmospheric nitrogen by adding hydrogens,
making it bio-available to the soy-bean plant.
Katie: Jolly good. And how can we feed the soil food web?
Marilyn: By adding finished compost. There is a lot organic material in compost, so your providing a food source for the microorganisms as well as inoculum of good-guy, beneifical microbes.
In this way you’re jump starting the soil food web and ensuring the that the microbes will grow and survive there.
Chris: So you make a compost pile and you spread it out. That’s how you grow
microbes. Or make a compost tea or compost extract to grow your microbes and spread it around.
Marilyn: Chris brings up a good point. When we arrived at Navdanya at the end of November, first things first we started making a compost pile
. We’d already looked at a few samples under the microscope and saw that most of the fields here at Navdanya were bacterial dominated and, since learning about the soil food web and based on our experience over the past couple of years, it seems to us nine times out of ten you’re going to have to add beneficial fungi to the soil.
So, with the help of many interns here at Navdanya, we made a fungally dominated compost pile. That means that roughly:
· 50% of the compost pile was carbon – woody material and a lot of dry leaves – fungal food
· 25% regular nitrogen – food scraps, green plant material
· 25% high nitrogen – cow dung – both bacterial food
By making a fungally dominated compost, you can use this as a source of good-guy fungi and bring balance to the soil microbial life – that means balance between bacteria and fungi.
Katie: And can I just ask a clarifying question? If we cut our grass and put those cuttings on the compost, or if we prune a tree and put those branches on the compost – are we adding carbon or nitrogen?
Marilyn: You have to think about the life cycle of the plant. If you cut a plant that is actively growing, i.e. actively photosynthesizing, and storing sugars, the cuttings will be a nitrogen food source for the bacteria. They will be a “green” plant material. Even if you let the grass dry down and a few days later it’s brown, it’ll still mostly be nitrogen and will feed bacteria.
Versus if you rake leaves, say in the fall, where the tree retrieves all of the sugars and nutrients from the leaves before it sends out hormones to tell them to drop. As the tree retained its nitrogen sugars before going into its dormant winter state, the fallen leaves will contain more carbon than nitrogen, which is a great food source for the fungi.
Katie: So obviously with your wonderful microscope and high tec lab here at Navdanya, you’ve been able to assess the soil and see that it has been mostly bacterial. But if we don’t have a microscope back home, how do we gauge what is happen in our soils? And how might we then alter or re-balance the soil?
Marilyn: Sure, alright. A couple of things you can do, looking at the colour of your soil can give you an indication of how much organic matter it contains. For instance, there’s a lot of sand here at Navdanya, this white colour indicates a lack of organic matter. And we’ve just heard from Vandana Shiva about two hours ago, that when they bought the farm back in 1987 the soil was all sand, and the water would flow straight through and nothing was retained in the soil. So Negi Ji, the head farmer here at Navdanya, has added lots and lots of organic material to help build the soil structure. And when I say this, I mean the microbes build the soil structure, the organic material is simply a food source for the microorganisms.
Chris: Also, using the idea of succession – the idea that, if left undisturbed, a piece of land will continuously change from annual crops to scrubs to soft woods to hard woods, and from a simple soil food web comprising solely of bacteria to a mix with fungi to a more and more complex web of microbes in turn. But each time you plow, or set fire, or turn the soil – the process of succession is pushed back to a more weedy, bacterially-dominated soil and “Mother Nature” has to come in and heal the land again, back towards a more fungally-dominated forest environment.
So you can look to see what “Mother Nature” is putting in your yard. And if “Mother Nature” is putting a lot of weeds into your yard…
Katie: And what do you include as weeds?
I would say anything that’s fast growing and sets out a lot of seeds. But this could be a food source, for instance amaranth is fast growing and sets out lots of seeds.
Katie: OK. SO fast growing plants indicate that there are lots of bacteria in the soil?
Marilyn: Yes, that’s definitely true. If you looked at a soil for example, maybe a plot on this farm, and you saw all sorts of weeds, you can tell that it is a bacterially dominated soil. And if you didn’t want them there you can
add a little more fungi from your fungally-dominated compost pile to discourage their growth.
Chris: I think it’s fair to say that in most situations, soils are more bacterial than fungi, because fungi takes longer to establish and is further down the succession chain. It takes more care to propogate the fungi than the bacteria, which will grow anywhere. Nine out of ten times the home gardener is going to need to add more fungi to create more balance.
Katie: Have you noticed much of a difference between organic and chemically fertilized soils that you’ve tested here at Navdanya?
Marilyn: We’ve had the good fortune to train about sixty farmers through the Navdanya farmer training programme. During the last training, Negi Ji asked some of the farmers to bring in their chemically treated soils, and by this I mean urea, which is really popular here in India to add to the soils. Inorganic urea is salt based and salts dries out and kills the microbes, so when we looked at the soil we saw only a little bit of bacteria and hardly any organic matter – the soil was essentially sterile.
When we compare Navdanya soils, they have a lot of organic material, and as we said earlier some of the plots are bacterially dominated, but others have flagellates and protozoa, and some nematodes. Any of the plots that have a mulch on top have really good microorganisms, meaning microorganisms from all different trophic levels of the soil food web.
Katie: Can you tell us some of the things that Navdanya does that we should emulate?
Marilyn: Well, first thing, back to the organic material – this is so critically important. You have to provide a food source if you want a lot of microorganisms in your soil.
Compost, there are so many different types of compost here at the farm. We’ve found one that’s called the Cow Pat Pit, that seems to be loaded with good-guy nematodes. Nematodes are higher up on the trophic level, and they are particularly interesting because they are pretty big so they’ll only be in areas where there is a lot of good pore structure because they need to be able to physically move around – so there needs to be lots of bacteria and fungi making good pore structure so the nematodes can do their thing. For instance, they are excellent at cycling nutrients, they eat everybody else in the soil, so they’re always mineralizing and excreting a lot of nutrients. Therefore they are an excellent nutrient cycling source in the soil.
Katie: And what are some of the things, coming from your permaculture and science background, that you hope Navdanya might consider changing or other gardens elsewhere might want to consider?
Marilyn: In our base line assessment, we noticed that a lot of the agricultural fields that are not mulched are bacterially dominated. We haven’t seen a lot of fungi, we haven’t seen a lot of nematodes, microarthropodes and other microbes that we would hope to see. SO one thing we could change, would be to add more mulch (covering bare soil with leaves and straw) to their soils. This would first of all, preserve water, essential in a sunny environment like India where water is a precious resource. Mulch also creates a great environment for the microbes to grow.
Chris: Yeah. Mulching and protecting the soil. The head farmer is a little leary about mulching thirty acres of soil, that’s why we’re also working with him on creating these different fungal preps, dilutions of fungal compost and spreading those on to the fields to add the missing nutrients, which he seems to be interested in.
Katie: Thank you so much!
For more information on the Soil Food Web check out Dr Eliane Ingham’s website and work here.