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Ecological Weeding - We Succeed the Weed
Weeding you Down the Garden Path
If You Can't Eat Them, Succeed Them
Nature always tries to cover bare soil, using fast growing, ground-hugging pioneers. But weeds are only a temporary phase in the natural succession of plants and eventually allow other less hardy species to establish themselves in their wake. Planting crops that cover the ground in a similar way, means getting rid of weeds ecologically.
Weed close to the plants' root area, leaving soil else where undisturbed. This allows the plant to grow at the same rate as the space occupied by weeds shrinks. In the undisturbed soil the fertility and structure of the soil improve, and the weeds finally give way to the planted specimens.
"Whenever we get ourselves into a muddle about how to handle weeds, we remember our weed motto: If You Can't Eat Them, Succeed Them!" say Kim Wilkinson and Craig Elevitch of AgroForestery in Hawaii. " After all, weeds take farm land in the same direction we want it to go: towards more diversity, resilience, and abundance. Most of the plants that we call weeds are involved in the primary stages of natural succession. They are medicine for the soil, repairing it and revitalizing life.
“Play the weed's game,” continue the groundbreaking duo. “The name of the game is succession. We have to be more appropriate than the weed, and make the weed's job obsolete. In short, we succeed the weed. It is counterproductive to focus on fighting weeds, since after all they have the land's best interest at heart. Besides, we can't win. They have been excelling in the process of succession for many more generations than we have.“
As above so Below
Down in the garden, weeding the strawberry patch, I notice that the biggest strawberry plants grow right next to the biggest dandelions. The competition appears, paradoxically, to be mutually beneficial. Where weeds are non-invasive, they can often work with, rather than against, the gardener.
Dandelion and dock roots deeply penetrate and loosen disturbed or compacted soils, as they forage for minerals. Their overhanging leaves provide shade, keeping the soil at the cooler temperatures soil organisms prefer, as they reweave the soil's structure and fertility. However, keeping the ground covered and largely undisturbed, does not necessarily imply a weedy garden.
The agroforestery team explain that, “soil microlife feeds off plants. The diversity of plants on the surface is directly related to the diversity of microflora in the soil. Weeds can contribute greatly to that diversity, as well as providing insect habitat, and encouraging birds. A healthy mix of insects encourages balance and reduces the chance of insect 'problems'. So, having remembered that weeds are useful, particularly as food for soil life, people, animals, and plants, we can use them as a resource. But, what about when it looks like the weeds are eating the crop plants, and not the other way around?”
Fungi and Fleming
The End of the Tedious Two Step.....fill the Gap
Kim and Craig explain that “in the natural process of succession, weeds establish where they find a place, usually in open or partially open conditions, especially on bare soil. They modify the environment, eventually making the area inhospitable (too shady, etc.) to more of their kind. Other plants come in who thrive in the modified conditions, and the process of succession continues until the ecosystem is more or less stable, usually culminating in a closed-canopy forest.”
By observing the territorial skirmishes of soil organisms below ground, the dynamics of “live and let live” can be observed and understood. Fungi compete with bacteria in the soil by producing antibiotics. In order to survive in this hostile environment, bacteria develop resistance through genetic mutation. However the fungi have learned that the presence of an antibiotic only kills off the susceptible bacteria and favours the growth of mutants. These new strains are no longer harmed by that antibiotic, and are later able to counteract its effects. Escalating soil wars would be mutually depleting for both colonies, so the fungi grudgingly allow the bacteria their place in the soil. The threat of a stronger antibiotic is their only trump card. By trying to remove the competition, they find they provoke even more.
The work of Alexander Fleming in the 1920s showed that moulds, such as Penicillin, can produce antibacterial chemicals. Later, many antibiotics were isolated from soil samples containing fungi. As bacteria have the ability to develop resistance to almost any drug they are exposed to, Dr Fleming warned, in an interview with the New York times in 1945, that “the misuse of penicillin could lead to the selection and multiplication of mutant forms of resistant bacteria”. This resistance is now threatening our ability to treat infections, not only in humans but also in animals.
The routine use of antibiotics in animal feeds to enhance growth has lead to commercial animals now hosting bacteria that are resistant to many antibiotics at the same time. Multi-resistant bacteria can spread from the animal to the human via feeding and handling or through contaminated soil. These interactions between humans and animals can alter the bacterial flora of each. The cycle goes all the way round, with humans now facing multiresistant bacteria caused by unrestrained or inappropriate use of antibiotics. The lessons learned by the fungi, are now beginning to make sense.
As Outside so Within
In this sense, weeds can be likened to bacteria. Some are the “good bacteria” that cannot kill the disease-forming, or pathogenic, bacteria but limit their growth by taking their place. Like the soil's living surface layer, the body's natural flora and fauna support the health of our inner membranes. These helpful inhabitants are less resistant to the effects of antibiotics and are wiped out easily, leaving the body vulnerable to the establishment of the pathogenic strains.
In a similar vein, the use of weed-killers, kill the soil organisms along with the weeds. This leaves the soil weakened and thus more inviting to weed colonisers. The weeds that can withstand the planticide residues and poor soil conditions, reestablish their presence. These are often, the tenacious, invasive weeds such as thistles and bindweed, that have adapted multiple ways to ensure their propagation, and are the real frontier farmers of the weed world.
However, even Kim and Craig suggest some situations may require the appropriate use of weed killers. “As a last resort, or in areas where the weeds are just too overwhelming, we may need to take a step back in the succession process. This may involve sheet mulching with a thick weed barrier once, baring the soil once, or even spraying herbicide to kill grasses one time. But we have to remember that this is a step back from the natural process of things, and the next step is the weed's turn. Unless we want to be involved in a tedious two-step (we remove weeds, they come back, we remove weeds, they come back) for the rest of our farming career, we need to take two steps forward immediately after taking the one step back. This means mulching and filling the space with appropriate plants (groundcovers, crop trees and other vegetation), creating a healthy system with no room and no need for voracious weeds to modify it. Farming in the tropics does not need to be a routine; it can be an evolution, an upward spiral. That is how we know we are doing it right; when it is easier for us with each passing season.”
Keep it Green
The Soil Eats Organic
Down in the strawberry patch, I did weed out a whole pile of weeds, and laid them immediately back over the exposed earth. That night it rained and I could imagine the water trickling down the channels their roots had left behind. I chose the weeds I saw overpowering newly emerging seedlings. And like the presence of good bacteria which prevent pathogens establishing themselves so I left the weeds that seemed to encourage growth where they were. When laid back on the ground, the weeds provide mulch and raw materials to renourish the soil. Mulched ground is easy to weed as it preserves soil moisture and soft topsoil structure.
“Organic matter needs to cycle through the soil for nutrients to get to plants,” explain our Hawaiian weed team. “Cutting weeds back and mulching plantings with them is a common practice with tropical farmers, and increases crop plant health. It is best to cut the weeds before they seed to keep the seeds from sprouting right next to the crop. Weeds also can be soaked in water in a covered container for about a week then fed to plants in a (smelly!) nutrient-rich liquid fertilizer tea.
Succeeding weeds is about stepping-up the process of succession. Filling the space with the trees and plants we want will leave less room for weeds. Some of the most aggressive weeds need full sun and low fertility to thrive; by increasing shade, organic matter and soil health they will disappear.”
A quick-growing living mulch, ground cover or green manure, such as alfalfa, can be used to suppress weeds in open ground. Identifying which weeds are growing can also give a good indication of what the soil may be lacking. “When choosing plants and methods to succeed the weeds,” explain Kim and Craig, “we take our cues of what is needed and wanted on the land from the weeds themselves. Weeds are experts in the process of succession, and great soil indicators as well, so we always look to them to learn what is appropriate. By imitating and accelerating what the weeds are doing, everyone succeeds.”