A weed control theory.. what do you think?

[Chipdasqrrl]

I was just thinking about how plants are adapted to certain ph ranges, and as you probably know, alfalfa does well in alkaline soils. If you were to bump up a plot from a ph of ~5 to 7.5-8.0, wouldn’t that make for very poor growing conditions for the weeds that already exist there?
If you were to push a plot’s ph to the highest level that alfalfa can tolerate, don’t you think that would allow the alfalfa to dominate since there’s nothing in the seed bank that also does well in those conditions?
You might think that if that were the case, then it would already be a well known agricultural practice. If my idea turned out to be effective, I don’t think it would be a practical agricultural practice because it would be unnecessarily expensive to raise the ph so high.
What do you think? It might be worthy of a little test plot.

 

[Cap'n]

I was just thinking about how plants are adapted to certain ph ranges, and as you probably know, alfalfa does well in alkaline soils. If you were to bump up a plot from a ph of ~5 to 7.5-8.0, wouldn’t that make for very poor growing conditions for the weeds that already exist there?
If you were to push a plot’s ph to the highest level that alfalfa can tolerate, don’t you think that would allow the alfalfa to dominate since there’s nothing in the seed bank that also does well in those conditions?
You might think that if that were the case, then it would already be a well known agricultural practice. If my idea turned out to be effective, I don’t think it would be a practical agricultural practice because it would be unnecessarily expensive to raise the ph so high.
What do you think? It might be worthy of a little test plot.

You might very well just trade out the weeds that like acid soil for weeds that like an alkaline soil. Im sure there a sweet spot in there if you can find it. I dont know how much ag lime is but I would think it would take at least 2 tons an acre to move it a point depending on the soil type.

 

[catscratch]

It's a practice that is at least somewhat known. Research dandelions and pH. I say go for it, but like said above you might just be trading for something else.

 

[MarkDarvin]

That might work for a while, but you can't have a winning football team that is all quarterbacks.

Weeds are an expression of what's going on in the soil. Easiest example is clover in your lawn, or grass in your clover plot. Soils will promote balance as imbalance is created by single species plantings. All grass invites clover, all clover invites grass, compaction invites dandelions, low calcium invites cocklebur, wetness brings sedges, total death brings pioneers like thistle and curly dock.

Iron and glyphosate have thwarted the display of this lesson for many years, but this is a skill that's going to need to be relearned as gly's effectiveness wanes.

I learned the hard way with thistle in pure clover on high ground, and horsetail (not marestail) on wet ground. Horsetail is 100% resistant to gly. It also thrives in wet, low pH, high potassium soils. I cleared the deck with gly and my quest for 6% K, and the horsetail swamped the whole damn thing. I can't tile, so my only defense was to get my pH up from a low 6 to near 7 (was shooting for 7). I just got the lime on last fall, so we'll see how i did come June.

 

[MarkDarvin]

I'd find a different path. You're gonna start losing forage quality as you go north of 7.5.

 

[dogghr]

Lots of natural so-called weeds that deer love to browse various times of the year. Better question is how to copy what nature is wanting to do. She abhors mononculture golf course type landscapes even if it is alfalfa.
But in answer to your question within reason yes amendments can help promote certain plants while inhibiting others.


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[BenAllgood]

I was at the library last week, and there was a book titled, Weeds : control without poisons. I didn't check it out. It talked about this. I flipped through it and it had some pretty interesting concepts.

 

[Chipdasqrrl]

You might very well just trade out the weeds that like acid soil for weeds that like an alkaline soil. Im sure there a sweet spot in there if you can find it. I dont know how much ag lime is but I would think it would take at least 2 tons an acre to move it a point depending on the soil type.

I think you’re right that over time alkaline tolerant plants would begin to colonize. However, my thought is that these other weeds wouldn’t be present right away since they shouldn’t be present in the seed bank unless that ground was once high ph. I’m sure some weeds would still continue to come up, but it would eliminate or inhibit a lot of them

 

[Chipdasqrrl]

I'd find a different path. You're gonna start losing forage quality as you go north of 7.5.

View attachment 15197

Overall, nutrients might lose availability, but I wonder if that could be offset by the fact that the alfalfa would have less competition for those limited resources.
But of course even if that’s the case, the downside would be that those unavailable nutrients would probably leach out of the soil

 

[Chipdasqrrl]

Lots of natural so-called weeds that deer love to browse various times of the year. Better question is how to copy what nature is wanting to do. She abhors mononculture golf course type landscapes even if it is alfalfa.
But in answer to your question within reason yes amendments can help promote certain plants while inhibiting others.


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I was hoping you would reply, I like to hear your perspective on these types of things.
How do you think nature would react to this drastic shift to a ph to 7.5+? I would imagine that there is not much present in the soil that is adapted to those conditions.
How would Mother Nature balance out this new environment that likely favors a non diverse stand dominated by alfalfa?

 

[X-farmerdan]

Weeds are weeds because they are very adaptable. Don't have the time, but I think we might find that "most weeds" survive and or prosper in a wide range of soil pH. Getting the soil pH right for you desired plant makes them more competitive and presents the possibility of outgrowing and out competing weeds.

 

[dogghr]

I think xfarmer began to sum it up. Why is the weed the plant that survives drought so well? Why do they laugh at monsoon years ? Why do they outcompete anything a farmer wishes to grow? So adaptable by nature to reestablish nature’s plantings. You are asking to change the course of thousands of years in a short window. Perhaps nature wants the soil at 5.5 despite our/ my efforts to change that. Perhaps the meadows , perhaps the oak forests , perhaps the conifer savanahs are quite happy and most productive at nature’s soil conditions she deems.
As for the weeds, deer browse on so many of them by stem or leaf or seed pod at various time of year. Even the thistle I hate and spray is loved my the monarch butterfly as it blooms.
I’m not going to argue against amendments/ I’ll be spreading lime in a few wks but sometimes fighting all that is natural can be expensive and frustrating even for a profit farmer.
Let us know how your experiment works. I was wrong... once.


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[BenAllgood]

And don't shortchange the weeds that are there or will show up when the pH is raised. This is an interesting study comparing alfalfa to different weeds showing crude protein and digestibility.
http://www.mitchellplainfarm.com/uploads/3/4/2/4/34242802/nutritive_value_of_common_weeds.pdf

 

[FarmerD]

I think if you control the weeds before you plant ..... amend the soil with lime and fertilizer per soil test for the crop you want to grow .... use the proper seeding rate to get the best canopy of plants, as quick as you can ..... plant at the right time ..... keep something growing for as long as possible ... keep tillage to a minimum ...... is about as good as you are going to get without cultivation and herbicides.

Understand what weeds/grasses you're trying to control and use some cover crops to your advantage.



I hate weeds and my Father could spot one at 100 yards, LOL ..... but like all plants there are some benefits. I just don't worry too much about some weeds in a food plot any more. Anything my weed wiper can't kill, I just don't fret about it.

 

[Chipdasqrrl]

Weeds are weeds because they are very adaptable. Don't have the time, but I think we might find that "most weeds" survive and or prosper in a wide range of soil pH. Getting the soil pH right for you desired plant makes them more competitive and presents the possibility of outgrowing and out competing weeds.

That’s a great point. Instead of taking everything else out of their element, maybe optimizing the conditions for the desired plant is the best form of weed control.
I think we focus too much on fighting the weeds ourselves, rather than helping our desired plants fight their own battle


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[Chipdasqrrl]

Thanks to everyone for sharing your thoughts. Sounds like it probably wouldn’t have great results, but I’m glad I asked. I would guess that weeds would still find a way, like they always do - and like some of you mention, that’s not such a bad thing.
I think I’ll still do a little test plot this year for the purpose of science.


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[Tap]

Weeds are weeds because they are very adaptable. Don't have the time, but I think we might find that "most weeds" survive and or prosper in a wide range of soil pH. Getting the soil pH right for you desired plant makes them more competitive and presents the possibility of outgrowing and out competing weeds.

I was going to mention the competition aspect, too.
But another consideration of the competition puzzle is the DPSM and plot size in relation to surrounding forages that are available. Small plots of highly desirable forages in areas of high DPSM are destined to have weed issues because the herd browses the good stuff and removes it from outcompeting the weeds. Its a problem I deal with where I live.

 

[MarkDarvin]

Thanks to everyone for sharing your thoughts. Sounds like it probably wouldn’t have great results, but I’m glad I asked. I would guess that weeds would still find a way, like they always do - and like some of you mention, that’s not such a bad thing.
I think I’ll still do a little test plot this year for the purpose of science.
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Do some exploring on the carbon to nitrogen ratio and why it matters. Your soil is always going to be attracted to that 24:1 zone. The further away you get, the more "weeds" you'll get trying to pull you that direction. When you get this right, you should see your weed pressure go down and your crop duff should get produced and consumed at the same rate.

 

[SwampCat]

Natural pH on my ground is 7.5. I have all the weeds common to less alkaline ground - and have more locust and cedar than most.

 

[Jason Broom]

It is an intriguing question, but as guys from northern Michigan, we sort of already know the answer.

When you start with really sandy "soil" that will grow lichens and ferns, then gradually improve the soil by increasing the pH and OM, the ferns go away and other stuff will grow more successfully. Yes, we usually plant specific things, at specific times, but that doesn't stop new weeds from colonizing this ground that we have accelerated the evolution of, with our concerted efforts. If you took the experiment even further, applying literally tons of silt and clay, carefully mixing and layering these elements of true soil together, the way nature does over millenia, you'd have some of the deep alluvial loams of the lower Midwest. There are weed problems to be addressed there, as well.

Nature abhors a vacuum, and seems to have a strong dislike for monocultures, as well. Instead of spending a lot of money trying to ruin your soil for all but a few plant species (hard to undo, by the way), learn from what nature does and figure out which blend of species would be symbiotic to each other, the soil itself, and to the multitude of fauna that might benefit therefrom.