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  • From: Road's End Farm <organic87 AT frontiernet.net>
  • To: Market Farming <market-farming AT lists.ibiblio.org>
  • Subject: Re: [Market-farming] Ingham on weeds (was Easy soil fertility test)
  • Date: Mon, 1 Nov 2010 13:43:40 -0400

But weeds are not some separate category of plant. Weeds are simply plants growing where a human doesn't want them to grow.

Strawberries are a weed in the lettuce. Brambles are a weed in the strawberries. Pasture grasses are a weed in the strawberries, the lettuce, the brambles. All of them are also crops.

Many of the weeds we're dealing with were introduced to the area by people who wanted to grow them on purpose -- often as food plants.

Amaranth, lambsquarters, etc. are "weeds of fertile soil" (and they themselves are also grown as crops; though usually different strains than the ones that show up on their own). I don't think there is any such thing as soil that will grow good crops, but will not grow any weeds: though soil in good condition for growing a specific crop (and "good condition" for blueberries will be different from "good condition" for corn) will tend to grow as "weeds" plants that want growing conditions suitable for the desired crop. "Weeds" that want growing conditions not suitable for the specific desired crop may indeed indicate a problem; and those specific weeds can be discouraged if the soil can be modified to better suit the crop; but other weeds will then be suited to the field.

Modern evolutionary theory doesn't talk about "higher" and "more primitive". It's true that some modern life forms are more similar to ancient ones than others, but everything has been evolving for the same length of time, after all. Different things are more suited to different conditions, but that doesn't mean they are more "primitive".

The percentage of the plant energy that's in the roots is going to vary from species to species and also vary with the time of year. I very much doubt that a 6' tall okra plant in full bloom has the same percentage of its energy in its roots as a carrot plant close to maturity; or that a redroot amaranth in full midseason growth has the same percentage of its energy in its roots as a Canadian thistle in late fall. To say that all the plants being considered by the farmer as "weeds" have 20% of their energy in the roots and all the plants being considered by the farmer as "crops" have 75% of their energy in their roots -- that can't possibly be accurate.

Most food crops have been bred for many generations by humans to produce in the fashion that humans want them to. In the process, most of them have become dependent on human intervention to do well, because they've been bred, not for best survival in a wide variety of conditions (including the conditions of competition from other plants, of variable availability of nutrients, of variable availability of water, etc.), but for best production of the portion of themselves that humans want to eat. This doesn't mean that they're "less primitive"; it means that they're adapted to a particular set of environments: those enviroments in which humans are an essential and helpful part of their ecosystem.

The "weeds" that grow best in a given field will be the plants that are best adapted to the conditions in that particular field. To the extent that the conditions in that field are as close as possible to the conditions that the desired crop wants, the desired crop will have less of a handicap relative to the weeds: so as far as that takes you, excellent soils (again, excellent for the particular crop) will certainly help the crop compete with the weeds. But there will always be weeds that also do well in those conditions, whatever they are.



-- Rivka; Finger Lakes NY, Zone 5 mostly
Fresh-market organic produce, small scale



On Nov 1, 2010, at 11:59 AM, Nan Hildreth wrote:

Yes, Dr. Shoemaker, many weeds evolved to fit a niche: disturbed or depleted soil said Dr. Elaine Ingham. Good soil thwarts weeds and plant diseases, she said.

In her class last month I scribbled notes like mad for the 2 days because this was so new to me. So it's good to try to explain it to you.

Weeds are typically more primitive plants than crops, says Elaine. Bermuda grass, she said is primitive grass that thrives when soil life is primitive, that is, three times more bacteria than fungal biomass. Weeds evolved to grow quick and produce tons of seeds then die. Weeds invest only 20% of their energy in roots while veggies invest 75%, fruit trees 80%.

Plants and soil biology co-evolved. Higher plants need higher soil life, that is more fungus than bacteria. Higher plants feed soil life with sugars from the roots. Half their energy goes into "root exudates" of sugars, carbohydrates and proteins that nurture symbiotic soil life. Ingham said plants putting out these "cakes and pies" for symbiotic soil results in them forming a "castle wall" around roots.

So you can grow more crops less weeds if your soil life is thriving and mature instead of abused.

Weeds also co-evolved to thrive where there is too much fertility she said. Thistle, she said, needs 50ppm nitrogen to even germinate. Nutsedge 10 ppm. But unlike veggies, they thrive if fertility comes in "pulses" for example, people throwing out fertilizer now and then. Johnson grass, dandelions too, she said. Weeds also like bad compost better than veggies. That is, compost that got too hot from too much manure, went anaerobic, and looks ashy or grey, she said.










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