weed control Archives

Weeds and crops are never equally healthy in the same soil

As soil mineral balance and microbial populations improve, the domesticated crops we seek to grow become healthier, and the pioneering plants we often refer to as weeds become less healthy.

Different plants thrive in soils with different microbial profiles and different mineral profiles. The soils which are optimally balanced for our domesticated crops are not optimally balanced for the pioneering plants we call weeds.

When the crop becomes healthier than the weeds, diseases begin infecting the weeds and leave the crop alone.

Here is pigweed on the edge of a disease-free tomato field in 2006. I don’t know what this organism is. I do know the plants only survived a few weeks more, and the tomato crop remained disease-free.

A question for you: Should the organism that is causing this infection be called a ‘pathogen’ or a ‘pest’? Or does that label only apply when they infect our crop plants?

John Kempf2020-06-24T07:06:08-05:00May 4th, 2020|Tags: disease, weed control, weeds|

Cultural management determines weed populations

An edited excerpt from the podcast interview with Klaas Martens:

The first year after you abandon a field that’s been in real crops—let’s say it’s been a corn field—think about what weeds will grow. Obviously there’ll be lambs quarter, pigweed, foxtail, velvetleaf, the whole range. They’re mostly seeds of weeds that make huge numbers of seeds. You may end up with millions of seeds per square foot on the field. But what grows the second year? Now from our reductionist way of thinking, we would assume that because we just made that many seeds, we should have a lot bigger problem with those weeds. But the second year, none of those plants are growing. We have other weeds growing there. And if you take that forward several more years, you start seeing goldenrod, woody plants, brambles, sumac—you know, all the thorny stuff and all the multiflora rose. And if you take it forward a few more years, you’re going back to forest.

This is something Dr. Albrecht wrote about. If you let it go for five hundred years, at least where we are, it would be back to old-growth hardwood forest—mostly oak—which Dr. Albrecht called the climax crop. That’s the kind of a steady state that nature would put the land in. This is how the land was made to work: it creates this succession where all of the species and communities—each one—changed the soil. And the reason all of those weeds that set seed didn’t grow the second year was that the plants that made them changed the soil, and that the right conditions weren’t there for those plants to grow the next year. So other plants grew. And that group, again, changed the soil, so that another group grew.

Now thinking back to what Dr. Albrecht wrote—he talked about these successions as actually being more productive, more diverse, and more vibrant than the climax crops. So that the tallgrass prairie and the oak would have been very stable, very resistant to invasions and diseases. Those plants didn’t get sick—they could tolerate flood, storms, whatever, and remain in very healthy condition. Albrecht used to tell his students to see what they were looking at—to see how nature does its crop rotation.

I started looking at a pest that forced me to start asking why it was there and what exactly it was doing in the soil. Take this back to the succession that we observe. Obviously, these plants are changing the soil, and left to their own devices, they kind of work themselves out of a job and something else grows. I had to look at everything that I could observe. I had to try to see everything there was to see—look at it through new eyes—look at it through something that is working exactly as it was intended to.

And the problem was me. If I didn’t like something, I had to own it and say, “This is the result of what I’ve done up till now. Now, how do I change that?” More importantly, how do I learn from it? So I started to study what these different weeds and pests do in the soil. And that grew into a system of how to read what the soil is saying and how to understand the language that the fields are using to try to teach us.

There was a weed that at one point I thought was going to make it impossible for us to farm organically. I was really frustrated. It seemed like this velvetleaf grew taller than the corn, no matter how carefully I cultivated—a lot of it always survived. I had a one-acre spot in particular where I ended up mowing it. The corn wasn’t going to be a crop—there was nothing developing. After about three or four years, it wasn’t quite as bad, and the area where the crop didn’t amount to much was smaller. Fast forward another three or four years, and lo and behold—my velvetleaf was getting into mid-summer and then it was starting to turn yellow. The lower leaves were turning brown, the lowest leaves had fallen off, and before the end of the summer it was dead. And not only that, but instead of being taller than the corn it was only about three to four feet tall.

So I called a friend at Cornell who is a lead ecologist. And I was still thinking completely wrong. I told him I had found a disease that was going to make me a millionaire. My brilliant idea was that we could catch those spores and make a product out of them. And my friend came out and looked the situation over. He said, “I’m familiar with these leaves, and you can go ahead with your plan. But before it can be successful, you need to explain this to me: why is it that when that disease is in your neighbor’s field, on his velvetleaf, it doesn’t hurt his velvetleaf?” And sure enough, this disease existed right across the road, and it wasn’t hurting the velvetleaf.

Now I should have been able to figure this out quicker than I did. But I have to admit, I was quite dense, and I needed quite a few lessons and to notice quite a few things before I started putting two and two together. The next thing we noticed was a second disease in that velvetleaf that a student at Cornell identified as a virus. And in the meantime, because I was paying so much attention to thinking that this was going to be my new product, I noticed that those leaves were covered with white flecks. The first time I saw it, I crawled on the ground and I said, “Look at all these white flecks—my leaves are just being eaten alive.” And the agronomist said, “You better watch out—you’re not going to have a crop left with all these insects out here.” But then we looked at the corn and there aren’t any bugs on the corn. The corn was perfectly healthy and growing well; it was only the weeds that bugs on them.

So the insects were actually carrying the virus, and the fungus was blowing on and killing them. But it wasn’t this complex that was actually killing the plants—those were just opportunists. We had changed our system so that it had become a very unhealthy soil environment for the weeds. And because the weeds were unhealthy, all these pests were moving in and were attacking the weeds. It wasn’t really the pests that killed the weeds—the pests were just there because the weeds were so sick they weren’t fit to live.

John Kempf2020-04-20T11:11:56-05:00February 18th, 2020|Tags: Klaas Martens, quality agriculture book excerpt, weed control, weeds|

Boron salts for weed control and as a desiccant

Recently I have received many questions about alternative forms of weed control, and if nutrients might be a possible means of control, specifically boron.

This is not an area where I have personal experience, and I am not personally familiar with how to manage boron applications to produce this effect. Test for yourself, with eyes wide open, and please let me know. I would love to learn more.

From what I have been able to read, it seems that boric acid and sodium borate can be used as an effective means of killing weeds. While the information I have been able to find is not particularly clear, it seems effective control is solution concentration dependent rather than quantity per area dependent.

Recommended rates I have been able to uncover are for either three ounces of boric acid or four ounces of sodium borate per gallon of water. Typically, boric acid contains 17% boron, and sodium borate usually contains 10% boron, so these recommended application rates don’t equal the same quantity of applied boron on a per-acre basis.

We need to be aware of the quantity of boron being applied on a per-acre basis, and the boron sensitivity of the crops we are growing. In our agronomic recommendations, based on soil analysis and plant sap analysis we often recommend between one and three pounds of actual boron per acre per year. The rate varies with the crop, soil levels of boron, and annual rainfall. In low organic matter soils, ten inches of rainfall can leach about one-half pound of boron per acre. Thus, if you get forty inches of rainfall per year, you need to add two pounds of boron annually just to replace what the rainfall removed. As organic matter increases, and soils anion exchange capacity increases, less boron is leached through the soil profile.

If we follow the recommended concentration rates, and apply 20 gallons of solution per acre, with each gallon containing four ounces of 10% boron, this application will give us eight ounces of actual boron per acre. This rate is well within the range of what is routinely applied as a soil amendment or nutrition source of boron on many soils and crops. This type of application would also supply much more uniform soil distribution than a broadcast application of pellets with some distance between the pellets as occurs with such small application rates.

Obviously, this application is non-selective, and should not be applied directly on crop plants.

With the exception of a very few boron sensitive crops, I do not expect that boron toxicity to the crop is nearly the danger that it is sometimes made out to be. Boron toxicity in most plants is simply a calcium deficiency. In cases where excessive boron was applied in the past, a foliar application of calcium will snap a crop out of boron toxicity in a matter of days, even when tissue analysis levels are ten times higher than desired values.

What these experiences suggest to me, is that using boron salts as an herbicide is likely to produce the biggest effect on calcium deficient soils and that soils with adequate or generous calcium may require stronger application rates to produce the same effect. Of course, crop sensitivity to the boron application will also depend on soil calcium levels.

It is important to mention that using boron as a form of weed control is specifically prohibited under USDA NOP rules for organically certified producers. It can be used as a nutrient source with restrictions, but not as an herbicide.

If you would like more information on the toxicity of boron in the environment, the National Pesticide Information Center link provides very thorough and useful information.

National Pesticide Information Center

EPA Boric acid restrictions on boron in crops (based on used for insect control in grain storage)

John Kempf2020-03-16T14:00:49-05:00February 7th, 2020|Tags: boron, weed control, weeds|

Electromagnetic Weed Control

Would you have guessed that it is possible to prevent weed seed germination by exposing them to a specific electromagnetic signal?

In 1991, Phillip Callahan1 first published his experiences with a uniquely designed cultivator tine that produced a frequency which inhibited weed seed germination. I am not aware that anyone has picked up this research, which seems like such a golden opportunity. Now is the time! If you know of anyone who has done work in the area, I would love to learn more about it.

Enter Phillip:

Not so very long ago I was dining with my editor, Charles Walters. I was at the 1991 Acres USA convention and Mr. Walters introduced me to an Australian gentleman seated at the same table. Our Australian friend, John McCabe, was attempting to explain how a cultivator he had modified completely eliminated weeds from his crop fields. Both Mr. Walters and I had a difficult time understanding the modification until Mr. McCabe showed us a photo of the tines on the cultivator.

Each rake like tine had a full loop along its length (see photo). In other words, each tine was a one-loop spring. It was quite obvious that each spring-loaded tine would vibrate at some low frequency made as it was dragged across the soil. The tractor vibrations would also vibrate each tine. The vibrations would enter the soil as sound since the spring would beat against the soil particles. Sound waves are pressure waves, but such a system would also have a low frequency electric radio wave associated with the sound wave. The sound wave would not penetrate the soil for any great distance since it would be muffled by soil. Low-frequency radio waves, however, penetrate to great depths in both water and soil. This is why the Navy utilizes low-frequency ELF radio waves to communicate with the atomic subs underwater.

We may understand now that common sense tells us that low-frequency, radio, especially below 1000 Hz must be significant to seeds and roots. These frequencies, even the atmospheric Shumann frequencies, easily penetrate the soil to both seeds and roots – light does not! Why study the effect of light below the soil when it is not light, but ELF radio that bathes the seeds and roots?

As far as I can determine from the literature, not a single scientist other than myself is concerned with ELF radio waves in the soil. If my thesis is correct, then a simple spring-loaded soil experiment should prove whether or not the spring-loaded tie imparts ELF radio waves into the soil. I, therefore, buried my PICRAM antenna – detector under 4 in of soil (seed depth).

Whenever I plucked a rubber band, mounted between two nails, the radio electric field penetrated the soil to my buried PICRAM detector. I could hear the sound of a rubber band in the air above the soil, but the weak sound would not penetrate the soil to a microphone below.

The sound is blocked by a few inches of soil, but the low frequency radio wave from the rubber band is not. From directly on the soil surface, to as far away as one foot above the soil, the PICRAM underground resonated to the fundamental frequency of the snapped rubberband. The frequency range for rubber bands occurs at 140 Hz for larger strong bands to a slightly higher frequency of 150 Hz for small weak bands – a range of about 10 Hz depending on rubber band size and strength.

The top Figure (1) shows the waveform at a fast sweep 5 ms (5/1000 of a second). Waves are calculated, of course, by how many occur in 1 second (One wave per second equals one Hz). Since wavelength, the distance from crest to crest is the number of waves (frequency) divided into the speed of light which is 186,000 miles per second, then the wavelength of a 140 Hz wave is:

In other words, the fundamental ELF radio frequency of a rubber band at 140 Hz equals a wave from crest to crest, 1328.5 miles long. Every time you snap a rubber band a radio wave of from 140 to 150 Hertz not only passes through the soil but also passes through your body – a mighty long wave!

The bottom sweep at a slower speed 50 Ms (50/1000 of a second) shows how the 140 Hz slowly dies out as the vibrations get weaker and weaker.

The tines on Mr. McCabe’s cultivator may or may not resonate in the same region (being a metal spring probably not) but what is certain is that they resonate somewhere in the ELF radio range between 1 and 1000 Hertz, and wherever it is, that particular tine frequency is bad for weeds and good for crops in the same way garlic can be good for digestion and bad for love.

Nothing is certain in this world, but if the peculiar Australian cultivator is doing what Mr. McCabe claims it to be doing, what is certain that with a trip to Australia, and a couple of days in those weed-free fields, it would take less than half an hour to determine the fundamental frequencies of those spring-loaded tines. That makes control of weeds as simple as generating that frequency.

(Since I wrote this in 1991 I traveled to Mr. McCabe’s farm and measured his cultivator with my PICRAM. It resonated at 720 Hz so I did not miss it by far. It is an ELF frequency!)

It is obvious that the weed seeds must store the wavelength information that causes them to go into dormancy, for the cultivator passes over any one seed in seconds.

An electronic ELF generator could be designed to transmit those ELF waves into the soil. Attached to any cultivator it would most certainly not poison the soil, for no frequency has ever been known to hang around after it has been switched off. Furthermore, the costs would be thousands of times cheaper than chemical weed killers for you buy it only once. I need hardly mention that not only do chemical weed killers kill weeds, they kill people also – Agent Orange!

From this simple weed – radio experiment my readers, I hope, will be left with a feeling for the importance of understanding the electromagnetic portion of the spectrum. By eliminating chemical poisons, fertilizers and such sick techniques of agriculture, we may not only eventually control diseases, but also increase agricultural output without destroying our spaceship earth.

Callahan, P. S. Exploring the Spectrum: Wavelengths of Agriculture and Life. (Acres USA, 1994).

John Kempf2020-03-16T13:51:11-05:00January 8th, 2020|Tags: weed control|