Do weeds rob soil of nutrients?

Wholy Cow, what an awe inspiring discussion this thread has become, glad I've been watching in on the side lines.
Lots of great ideas and answers.
Tim, great subject for this thread, thanks for starting it.
Everyone else, fantastic responses.

weeds are one of my favorite subjects, it is interesting to see what others views of these primary succession plants are and how they incorporate them, or exclude them.

Redhawk

Bryant RedHawk wrote:Wholy Cow, what an awe inspiring discussion this thread has become, glad I've been watching in on the side lines.
Redhawk

I was wondering what was keeping you from the thread, BR. And also, when I exclaim, it's "partially cow" so as to not invoke the whole cow, cuz, you know, that'd be wasteful. Hahahaaaaa

I personally leave all “weeds” that aren’t growing becoming excessive. I chop and drop everything. Sometimes I pull them. There is a loss of microbes, but it also does small scale aeration of the soil, give some take some..  

Welcome to Permies, Jas!  Glad to hear that this is working for you as well.  Where are you posting from and what sort of gardens do you have?

i always pile pulled weeds around my plants as a mulch layer. saves moisture and feeds my plants as it breaks down.

Hi Steve Bossie.  I'm glad that this works for you:

i always pile pulled weeds around my plants  

This would work with some of my weeds, but with many they would simply re-root and take off again (all my grasses, hawkweed, ox eyed daisies, hedge nettle, to name a few); this time they would root directly against my chosen crop plants.

Method A, for readily rooting weed use, make a green weed tea maker, it is almost the same as a compost tea set up, gives back most of the nutrients asap and leaves compostable, non re rooting stems and roots.
Bag the weeds for easy removal, brew for one week (this drowns the roots). The safe side would then lay the brewed weeds on some sort of screen in the sun to dry completely before adding to compost or using as mulch.

Method B, sun dry root systems of readily rooting weeds for one week before using as; a, mulch, b, compost material, c, worm food.

Method C, feed to hogs, they love most any weed and will process them for you.

(just some ideas)

Redhawk

Roberto pokachinni wrote:Hi Steve Bossie.  I'm glad that this works for you:

i always pile pulled weeds around my plants  

This would work with some of my weeds, but with many they would simply re-root and take off again (all my grasses, hawkweed, ox eyed daisies, hedge nettle, to name a few); this time they would root directly against my chosen crop plants.

i don't have that problem because i mulch every spring w/ 3in. of green wood chips around all my plants and trees. the few weeds that come thru get layed on top of the mulch. no N available plus the mulch desiccates them further= dead weeds! ;)

Bryant RedHawk wrote:Method A, for readily rooting weed use, make a green weed tea maker, it is almost the same as a compost tea set up, gives back most of the nutrients asap and leaves compostable, non re rooting stems and roots.
Bag the weeds for easy removal, brew for one week (this drowns the roots). The safe side would then lay the brewed weeds on some sort of screen in the sun to dry completely before adding to compost or using as mulch.

Method B, sun dry root systems of readily rooting weeds for one week before using as; a, mulch, b, compost material, c, worm food.

Method C, feed to hogs, they love most any weed and will process them for you.

(just some ideas)

Redhawk

my chicks ducks and geese love weeds! plus the dandelions, lambs quarters and other dynamic accumulating plants are chock full of nutrients. i have a section of lawn under my pines i intentionally let grow just to feed to my birds. the eggs yolks are a deep orange and taste fantastic! just planted a corner of the yard with more ''weeds''. borage and nettle for us and the birds. ;) funny you mention the tea. I've done it using just meadow grass and truthfully, the tea is as good as the comfrey tea i make. free fertilizer!

Tim Kivi wrote:Some permies say "there's no such thing as a weed". My gardening books all day that weeds rob the soil of nutrients meaning other plants can't access them.

What's the deal?

I've been putting on a mulch of pie seaweed on my garden bed. I top it with large dried whole maple leaves. Weeds and vegetables are all thriving. I have no problem with the weeds, unless my veggies could do better without the competition.

Now and then I simply pull a weed/grass out while picking my veggies, rip off the root from the leaves and drop it back on the ground as a mulch. Am I doing the right thing?

Now that I have a little time, I would like to address Tim's original question(s).

First let us look at the statement "there's no such thing as a weed" while true because all plants have their place in the workings of nature (which is to make soil rich enough to support life forms like microorganisms, worms, plants and all the other forms of life found on terra firma),
This precludes the term weed.  Humans call plants growing where they are not wanted "weeds" even a rose could be considered a weed if it is not in a place we want it to grow.  
All plants take nutrients from the soil, this is how they make their living and what allows them to grow, water is considered a nutrient.
So yes, "weeds" will take nutrients from the soil and since the plant fits the description of a weed when it grows where we want something else to grow, it could be considered a "robber" of nutrients.
Gardening books, for the most part, subscribe to the "modern agriculture" model, promoting localized monocrop growing (flower beds, etc. are usually designed to grow groupings of specific plants).
In gardening, most people forget that growing a single species of say Nasturtium in a garden bed, is indeed mono crop growing, even if it is so localized as to be a 2 foot square piece of a garden bed.

In nature what we call weeds are really primary or secondary succession plants, they have the job of putting roots into the ground, activating bacteria through their exudates which causes release of enzymes that dissolve minerals from rocks (dirt is ground up rocks).
So, when growing where we want them to grow, they are the good guys, if they are growing where we want something else, that isn't able to out compete the "weed" then they are a nuisance plant and are typically removed, taking with them the nutrients they have incorporated into their bodies.
If we just toss them to the garbage, we have lost those nutrients. If we do something else with them ending up back on or in the soil, then we have recovered those nutrients, thus saving the need to make an amendment to put back what we threw away.

Every one who has contributed to this thread already has brought this up in an excellent set of ways to put back the weed goodies. Bravo!

It is always the right thing when you use what you removed (plant material wise specifically) to make something you put back to the soil from which it was removed (recycling or closing the hoop of life), this works regardless of whether we keep some of it for our own food supply or use the whole plant as the new mulch, tea, or compost.  Nature wastes nothing, neither should we. One way or another we should always be trying to close the hoop when it comes to our soil, the more we succeed the better our soil becomes and the more life it will support for us.

Redhawk

Great conversation. I look at weeds as carbon fixators and nutrient accumulators and chelators, as well as soil conditioners. I do not worry about it if a “weed” is not shading out my wanted plants, it’s better than bare soil and trades sugars and nutrients via soil life that become more available to all plants around it.  Ultimately, Whichever plant has the greater photosynthetic surface area will ultimately win any transpiration powered tug of war for water and nutrients that may occur in times of scarcity. Unless you have more than enough organic matter in your soil, I’d let your weeds put it in there for you and chop n drop/feed to animals unless you have a choice plant to put there instead.

I have lots of docile ants who eat flowers. We also have horned lizards who survive on a diet of these ants.

Even if the weeds were not good for my soil, getting rid of them would cause much damage to the wildlife and my trees/plants.

I like the way they look too. 🙂

Ben Zumeta wrote:Great conversation. I look at weeds as carbon fixators and nutrient accumulators and chelators, as well as soil conditioners. I do not worry about it if a “weed” is not shading out my wanted plants, it’s better than bare soil and trades sugars and nutrients via soil life that become more available to all plants around it.  Ultimately, Whichever plant has the greater photosynthetic surface area will ultimately win any transpiration powered tug of war for water and nutrients that may occur in times of scarcity. Unless you have more than enough organic matter in your soil, I’d let your weeds put it in there for you and chop n drop/feed to animals unless you have a choice plant to put there instead.

i agree. bare soil is dead soil. when im not growing a crop, i either seed a cover crop or let the weeds do it for me. the reson they show up in the 1st place. mother earth doesnt like to be naked and exposed. ;)

I've been keeping a record as I find info of what nutrients different "weeds" accumulate.  All the legumes, clovers, vetches, bird's foot trefoil, black medic, etc. fix nitrogen from the air and add it to the soil directly or indirectly.  Yellow sweet clover accumulates phosphorus.  Creeping buttercups accumulate potassium.  Chickweed accumulates phosphorus and potassium.  Lambs quarters accumulates nitrogen, phosphorus, and potassium(doesn't get much better than that), calcium and manganese while loosening the soil.  Broadleaf Plantain accumulates calcium, sulphur,magnesium, manganese, iron and silicon.  Dandelion accumulates phosphorus, potassium, calcium, copper, iron, magnesium, and silicon while loosening the soil.  'Nuff said?

Ray

After reading something in the Mother Earth News, I set out to make a non-aerated tea from a few plants (comfrey, clover, lupine, and rose mallow), shaking the container a few times a day (I suppose it is aerated, after a fashion).  Sometimes a bit of composted chicken or goat poop, if handy, and some coffee grounds.  The recipe I read was for shredded comfrey leaves, grass clippings, dried chicken poop, and a bit of urine.

After the third day, it has a strong scent but it's earthy, not putrid.  I started using it as a tonic on plants that weren't doing as well as I wanted.  (I'm not sure if I want to get involved with getting the equipment to make compost tea.  I need to learn more.)

Then I began reading this thread.  It's got me thinking about understanding the soil food web, and returning the best, the essence, of the "weeds" to the soil.  My compost-making (like my "tea" brewing) is also fairly haphazard, and the chickens do most of the work.  I'm eager to improve my soil, and to find the balance between biodiversity and choked-out, shaded, or overrun vegetables!

So much to think about in this thread.

You won't get nitrogen back by harvesting weeds.

My method it collect grass cuttings in yard, go around with bucket and pick axe dandelions in yard, other weeds.

then drop them into my solar cooker trash cans.   Later put results on garden beds.

Plants gather most of tbe nitrogen they use from the air, soil nitrogen is used more by the micro organisms and the plant root tips. This means that most amendment nitrogen is not benefiting plants directly but indirectly through the organisms in the microbiome.

Redhawk

Bryant RedHawk wrote:Plants gather most of the nitrogen they use from the air, soil nitrogen is used more by the micro organisms and the plant root tips. This means that most amendment nitrogen is not benefiting plants directly but indirectly through the organisms in the microbiome.

Redhawk

Interesting point, we are usually taught about carbon dioxide + oxygen.  Like you point out there are many NPK, and other organic and inorganic things that play a in action for a garden.

Michael Moreken wrote:You won't get nitrogen back by harvesting weeds.

Three ways you get nitrogen back when harvesting weeds.

1.  You put that weed through an animal.  The cow, sheep or chicken harvests the weed and within a day, deposits it back out onto the ground in a N-rich form that is highly beneficial to the ecosystem.

2.  You compost that weed with a carbon source that captures the N rather than lets it gas off.  A properly constructed compost pile captures up to 80% of the N from the weeds/ingredients in the pile.

3.  A N-fixing weed has nitrogen nodules on its roots.  When harvested, that N is left below ground as the weed is chopped off at the soil surface.  If you don't harvest the weed, the plant will use it up by making seed, leaving little of it in the ground.

I grow a lot in large containers.
Often my containers started growing "weeds" before I'm ready to plant in them.
Sometimes its smartweed, sometimes lambs quarters, sometimes entire trees.
Once things get big enough to sort of identify , I "weed out" the less desirables and feedthrow  them to the chickens.
I don't know what part of it they eat, but they make it disappear really fast.

As a result, I have two barrels that are overflowing with cilantro , tomatoes, onions and a grape vine.
I only planted the grape vine and the onions, and I recently "weeded"  (pruned) the grape vine to keep it from competing for sun with the tomatoes!


The barrels that failed to sprout "weeds" have tomatoes starts planted in them.
They are puny compared to the tomato "weeds"
They had had a mulch of rabbit bedding applied last fall, and I transplanted a lot of tree seedlings out of them.
Now I'm thinking I should sow some "weed" seeds in with the puny tomatoes starts.


All told, the "weeding" I do is pretty beneficial for me.
Every weed suppresses some other weed, and seems to do the soil some good.
I get to interact with my gardens, and at a minimum I get a harvest of compostables.

Dynamic Accumulator Plants - plants that accumulate ten times more than usual of at least one nutrient.
 I'm not sure why the nitrogen isn't listed for any of the plants except the highest.....I assume all plants have quite a bit of nitrogen......

Ray, if there's a number in the chart is it 10x or is it only if it's highlighted that it's 10x normal?

Mike, the highlighted amounts are the highest for any plant tested of each nutrient or mineral.  By the way, you can click on the table to enlarge it.  Not all plants have been analyzed,  and I'm presuming the author couldn't find nitrogen values to add for all the listed plants.  As you may have noticed, lots of information is available for vegetables and even more for industrial crops.  But weeds have not received as much attention, and information is harder to find.  One has to "read between the lines"!  For example, I wanted information on the value of buttercups.  One site declared that in addition to being an undesirable weed because of toxicity to cattle, they rob the soil of potassium!  O.K.  Well the only way they rob a lawn of potassium is if you gather them up and send them off to the garbage collectors.  If you mow and mulch or compost them, why then they are potassium "accumulators" !

There was more information with the chart I posted and I'm going to try and retrieve and post it.  But I had a difficult enough time just being able to copy and post the chart, so we'll see if I can....

Ray

How does the nutrient content of comfrey compare to an average plant? A common claim is that comfrey contains high levels of nitrogen, phosphorus and potassium.
Two sources which analyzed comfrey came up with similar values of NPK which for simplicity can be rounded off to 3-1-5.
What is the NPK of some common plants?  That is not easy to find, but here are some found by Robert Pavlis:
• Alfalfa 2.5-1-2
• Clover, crimson 2-0.5-2
• Corn gluten meal 9-1-0
• Cotton seed meal 6-0.4-1.5
• Rye, annual 1-0-1
• Seaweed 1-0.5-1
• Soybean meal 7-2-1
Are these average plants? None of the above plants are dynamic accumulators by the definition used by Robert Pavlis, so they are not considered to have high NPK values. It seems reasonable to consider them to be average plants. When you compare comfrey at 3-1-5, it is not much better than the average list – it is certainly not ten times better.


If you download the chart here:   https://mega.nz/file/U8YySKjC#sh8Kr3H-IkPDAKFXIT1qD2uIh_zTYBT0K8_ybgQ6nNo

you can get a lot more information, especially long lists of many plants with their amounts of just Nitrogen, just Phosphorus, just Potassium, etc. etc. for the whole list of minerals.  Most of them are vegetables, fruits, or edibles, since that's what has been tested....