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Insects consume unhealthy ‘weeds’ growing in healthy soil

Not all plants grow equally well in the same soil. Each plant has a preferred microbial, physical, and nutritional environment it thrives in.

When soil balance is optimized for our domesticated plants, the crop plants are healthier than the weeds. Now, the weeds have lower brix readings, and are more susceptible to disease and insects than the surrounding crop.

These lambsquarter plants were growing at the intersection of three fields, growing tomatoes, mixed salad greens, and peas. The last two crops can be very susceptible to aphids. There were no aphids to be found anywhere on the crops, while the lambsquarter was being consumed, as you can see.

2020-05-16T12:48:30-05:00May 19th, 2020|Tags: , , , |

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?

2020-06-24T07:06:08-05:00May 4th, 2020|Tags: , , |

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. 

2020-04-20T11:11:56-05:00February 18th, 2020|Tags: , , , |

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)

 

2020-03-16T14:00:49-05:00February 7th, 2020|Tags: , , |

Weeds, Guardians of the Soil

We understand quite readily that different crops thrive in different soil environments. Blueberries require a different mineral and microbial profile than alfalfa, which requires a different profile than peaches. It should not be a stretch to realize that the same also holds true for the plants we call weeds. The weeds which grow most vigorously and abundantly in a given profile are indicators of the soil’s physical, mineral, and microbial characteristics.

There are several good books which have been written on this topic, particularly in the context of mineral profiles associated with different weed species, but one of the foundational books is from Joseph Cocannouer, titled Weeds, Guardians of the Soil, and framed specifically around his experiences as a farmer and agronomist in Kansas.

Here is an excerpt:

The late war in Europe, despite the suffering and destruction it brought about, gave birth to a new weed knowledge that should play an important role in rebuilding some of those ravaged countries. Necessity forced the investigation of the food value of many weeds that until then had been given a little attention. Some weeds that had long been looked upon as worthless were found to be a highly nutritious fodder for livestock. Once these weeds were correctly processed, that is, cut and cured into hay or made into ensilage, livestock not only devoured the hay and silage, but gave back gratifying returns.

American farmers will probably be more than a little surprised to learn for instance, that the detested bindweed, when cured into hay, gave returns from dairy cows considerably above either alfalfa or clover. Many weed experiments were carried on at one of England’s leading experiment stations, where the weeds, of course, were under control.

Thistles of several kinds, when treated correctly, were also found to rank high as stockfeed. Thistle ensilage is not entirely unknown in the United States. Stinging nettles, a European weed that is now established in many parts of our own country, the English investigators found to be excellent feeding, when cured, for both dairy cattle and poultry. These nettles are rich in protein, and laying hens, fed the cure leaves and stems as a major part of the ration, showed a marked increase in egg production. With dairy cows, nettle hay produced a very noticeable increase in milk and butter fat. Page 121

Lambs quarter is also a good weed, fitting into about as many niches as the pigweed. It is an annual and a native of Europe. As a general rule, lambsquarters may be found where ever pigweeds grow, and often as a companion of giant ragweed. This weed is a good diver and brings up much food material to the surface soil. It is an excellent green manure and makes an ensilage second to none when mixed with legumes. It is also a good mother weed if controlled, and one of the best potherbs of the whole group.

The giant ragweed, or horse weeds of the middle west, are a bit more exacting, preferring edges of cultivated fields, open forest areas, or sunny coves where they can grow unmolested. This weed will also take hold in hard land…

The giant ragweed has been used successfully for making ensilage. Page 159

~

What caught my attention, in particular, was the description of giant ragweed, ‘a bit more exacting, preferring edges of fields, growing unmolested’. Come again? Not the giant ragweed I know.

Other growers and agronomists with longer than five decades of experience have shared stories of how giant ragweed behavior changed. One farmer related “When we started spraying it with herbicides it was like pouring gasoline on a fire, now it grows everywhere and completely differently than it used to.

Mother Nature always bats last and laughs last. Trying to dominate natural systems with un-natural substances never seems to be a win in the end for some reason.

2020-03-16T13:57:57-05:00January 23rd, 2020|Tags: , , |

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