# Pre-emergents with alfalfa fields



## jenkinsfarmsinc

I am waiting until after "last frost" (sometime round first week of may) to plant my alfalfa but I'm noticing a fair amount of bindweed starting to come in. Has anyone ever sprayed, say roundup, before planting alfalfa? How long do I need to wait after spraying to plant? I don't want to kill off my seed and I don't want to fight weeds all year long. Thanks!


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## Vol

jenkinsfarmsinc said:


> I am waiting until after "last frost" (sometime round first week of may) to plant my alfalfa but I'm noticing a fair amount of bindweed starting to come in. Has anyone ever sprayed, say roundup, before planting alfalfa? How long do I need to wait after spraying to plant? I don't want to kill off my seed and I don't want to fight weeds all year long. Thanks!


7 days is all you have to wait after spraying a glyphosate until you can plant seed. You have time to spray if you are not planting until the first of May.

Regards, Mike


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## vhaby

Please correct me if I'm wrong on this one. Glyphosate has no residual effect and cannot be found once it contacts the soil. In late fall of 1999, we seeded a conventional alfalfa variety into a stand of volunteer ryegrass and turned around and immediately sprayed Roundup over the new seeding to kill the ryegrass. We achieved an excellent, weed-free stand of alfalfa. The labels for both Roundup Ultra and Roundup WeatherMax state that these producs can be sprayed before, during, or after planting alfalfa, but before emergence of the crop (Item 11.1 on Roundup WeatherMax Label on website below, pg 13). This same statement also applies for clovers, kudzu, leucaena, lespedeza, kanaf, lupin, sainfoin, trefoil, velvetbean, and vetch.

http://www.cdms.net/LDat/ld5UJ064.pdf

Vincent


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## TNKid

You are correct. I sprayed Gramoxone to burn down a field prior to seeding. It worked great and has no labeled wait time to plant. It should only kill anything with foliage. It is labeled for use on dormant alfalfa as well. It can be sprayed at a reduced rate in the first 5 days after cutting or when it goes dormant during winter.


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## Vol

vhaby said:


> The labels for both Roundup Ultra and Roundup WeatherMax state that these producs can be sprayed before, during, or after planting alfalfa, but before emergence of the crop (Item 11.1 on Roundup WeatherMax Label on website below, pg 13). This same statement also applies for clovers, kudzu, leucaena, lespedeza, kanaf, lupin, sainfoin, trefoil, velvetbean, and vetch.
> 
> http://www.cdms.net/LDat/ld5UJ064.pdf
> 
> Vincent


Oops, my mistake. There are planting instances where a seven day wait is recommended after spraying before planting and I incorrectly assumed that it also appled to alfalfa.

I am not 100% sure about glyphosate having no residual and I say that because on my RR alfalfa, it says to not apply more than 8 quarts of 41% active glyphosate in one year(weathermax is less than 6 quarts/ac) and that includes pre-plant burndowns during year of establishment. I believe that the following is in sec. 12.1 in your weathermax link. I find that recommendation confusing if there is 0% residual. Vincent, what are your thoughts on this?

Regards, Mike


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## slowzuki

Roundup reacts with components of the soil to become inactive. If you load the surface of the soil too much, I would assume it can because saturated so it won't react with additional roundup. I'd guess time, bacteria, oxidation and sun are needed to allow secondary processes to break down what round up becomes when it hits soil. I found this on the web:

"Glyphosate binds tightly to soil. It can persist in soil for up to 6 months depending on the climate and the type of soil it is in. Glyphosate is broken down by bacteria in the soil."


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## Vol

slowzuki said:


> I found this on the web:
> 
> "Glyphosate binds tightly to soil. It can persist in soil for up to 6 months depending on the climate and the type of soil it is in. Glyphosate is broken down by bacteria in the soil."


Well Slowzuki, that would confirm that glyphosate does have residual afterall.....guess many could learn from this.

Regards, Mike


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## vhaby

Here is an excellent read once one gets past the organic chemistry.

http://www.cdpr.ca.g...emo/glyphos.pdf

From the top of pg 4 on this site:
*"Soil:* In general, glyphosate is moderately persistent in soil. The primary reason crops can be planted or seeded directly into treated areas following application is that glyphosate exhibits essentially no preemergent activity even when applied at high rates (Franz et al. 1997)."


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## Vol

I think the thing that struck me the most in the Schuette report is the 98% excretion rate by rats etc. when fed glyphosate.....pretty phenomenal and pretty safe.

Regards, Mike


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## hay wilson in TX

*I have been instructed that the 7 day waiting period is to give the round up time to kill the plants down to the root before disturbing the weeds. *


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## vhaby

*Re: 7-day waiting period after spraying Roundup for weed control:*

A 7-day waiting period may be needed if one is to till the soil after spraying the weeds.

A 7-day waiting period is not needed if one is to overseed alfalfa into a tilled soil/prepared seedbed that now has a re-growth of new weeds that will shade out new alfalfa seedlings.


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