For your consideration, from the source

[Bowman]

https://www.monsanto-ag.co.uk/roundup/roundup-agriculture/best-practice/seed-germination/

The Effects of Pre-harvest Roundup on Seed Crops
If a crop is sprayed with glyphosate when it is still immature there may be translocation into the seed and subsequent germination will be affected.

In a cereal crop where ripening is relatively even the application should be made when all the seed is mature. This is because the application must be done at less than 30% moisture in the grain, (see recommendations on timing). Spraying earlier will stop further grain fill, leading to shrivelled grain and increasing the risk of residues of glyphosate in the grain.

Malting barley grains germinate as part of the malting process and it is particularly important to be sure the moisture content is below 30% to preserve the viability of the seed.

Crops which have indeterminate flowering have non-uniform maturation of the seed. Timing for pre-harvest treatment of peas, beans, linseed, oilseed rape etc. is always a compromise and to avoid the more mature seed being over-ripe application usually takes place when a proportion of the seed is still immature i.e. average seed moisture content is 30%. Hence germination of any seed retained will be affected. Seed which has taken up glyphosate may produce a shoot, (from seed reserves) and pass a germination test but can still be affected once it reaches cotyledon stage and starts to photosynthesise. So, even after adjusting seed rates, crop stunting and failure is possible.

The Effect of Debris on Germinating Seeds
When large amounts of debris break down in the soil, especially in wet conditions or where land is poorly drained, organic acids and phenols can be released as the environment becomes anaerobic, (no oxygen). In the same way large amounts of decaying foliage in aquatic situations can lead to de-oxygenation of the water and fish death. This phenomenon is often seen where large amounts of straw or chaff are left behind the combine and can result in poor germination and emergence of the following crop, when seeds germinate from the anaerobic layer. This can be minimised by thorough cultivation to disperse or bury the debris before drilling.

Where large amounts of weed material are killed by glyphosate and the target weed has a mass of roots, stolons or underground rhizomes, (like Couch), this can lead to the same effects described above on germinating seeds.

There is no direct effect from the glyphosate, but because it is translocated to all parts of the plant, the resulting death of all the plant material at the same time, can cause anaerobic conditions leading to a slight crop check. Cultivation will minimise such effects, but direct drilling and minimal cultivations into large amounts of trash are at the most risk.

It is for this reason that Monsanto do not recommend direct drilling in to long leys in the autumn where there is a surface mat.

Advice for use of Roundup
After spraying Roundup on high density populations of perennial weeds and establishing with direct drilling or minimal cultivation, there is risk of poor crop establishment unless thorough cultivation is carried out to disperse or bury the decaying organic matter.

Consolidation of loose soil, adequate fertiliser to aid breakdown and appropriate measures against insect and fungal damage are also advised to achieve the optimum results.

Autocast Oilseed Rape Establishment
Autocast establishment of oilseed rape has been around for some years, though is less used now than 5 years ago. With an even spread of straw and plenty of moisture shortly after harvest it can work well. However, there is the potential for unreliable and uneven establishment where straw and chaff spread is uneven. There is a high degree of inherent variability with the autocast system, and poor germination can occur irrespective of a pre-harvest glyphosate treatment, due to high straw levels, compaction, slugs, and weather conditions.

Straw breakdown is slower over Autocast crops, particularly if anaerobic conditions are present, under thick mats of straw on the surface. The straw is not in intimate contact with the soil so breakdown of glyphosate residues left on the outside of the stems will not be rapid, due to a lack of both microbes and moisture. This means a theoretical danger of subsequent rain washing residues from outside of the straw onto the emerging oilseed rape seedlings – if this occurs the effect would be the same as spraying and could cause damage. The highest risk is where no rain falls between spraying and harvesting/autocasting. Heavy rain between the two operations will reduce the risk of subsequent damage.

Conventional drilling, direct drilling and many other reduced cultivation techniques, can all be used successfully after pre-harvest application of Roundup, but Monsanto does not recommend Roundup with the original Autocast mounted on the combine.

• Straw from a crop receiving a pre-harvest treatment is not recommended for use as a mulch. This is effectively what is being achieved with the original autocast system, where seed is broadcast behind the cutter bar on the combine and then covered with a layer of straw and chaff.
  
  
• When establishing subsequent crops straw should be at least partially mixed with soil, but does not need to be completely buried. Any system which involves even a light cultivation or soil disturbance e.g. the Opico Variocast or Terracast seeders mounted onto various cultivation equipment ensures that any glyphosate residue remaining on chopped straw is broken down rapidy by microbial activity
  

Note: Under all other cultivation systems straw and any glyphosate residue will be broken down rapidly by microbial activity even when only partially mixed in the soil by cultivation.

I will respond to comments.

 

[MarkDarvin]

What conclusion are you trying to share here? Is it that spray/throw/mow doesn't work?

I appreciate the contributions to ag that Monsanto has made, but the majority of this piece just isn't so. Where would there be an anaerobic layer in mowed straw? There'd be far more air in mowed straw than tilled straw. Short term the soil would be hyper oxygenated with tillage and carbon (straw) would be rapidly consumed. But quickly after the tillage, soil will settle and air will be pushed out and the soil would return to a state of collapsed pore space. Guess what that requires... more tillage.

If you had anaerobic conditions below the soil surface, there would be no straw at all because nothing would have grown. Shying away from a heavy residue is bad advice, and shows a misunderstanding of soil structure and C:N balance in the soil. Look no further than your typical bean field. Soybeans planted into heavy corn residue on the surface thrive compared to soybeans in heavily tilled soil. Less soil splashes up on the plant (which reduces disease), soil temps are moderated, moisture is better retained, and rhizobia feeds off the carbon enabling them to affix nodules to the roots of legumes.

Crops heavy in either carbon (corn, wheat, oats, sorghum) or nitrogen (beans, clover, peas, vetch) need to either be blended or alternated to maintain balance. You'll know quickly if you're out of balance, because that's when you need to break out the chemicals and diggers to rectify your imbalance.

This is why homeowners are constantly fighting clover in their grass, and plotters are fighting grass in their clover. The soil is trying to balance itself, and we're fighting against it.

https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1166766.pdf

 

[Bowman]

What conclusion are you trying to share here? Is it that spray/throw/mow doesn't work?

I appreciate the contributions to ag that Monsanto has made, but the majority of this piece just isn't so. Where would there be an anaerobic layer in mowed straw? There'd be far more air in mowed straw than tilled straw. Short term the soil would be hyper oxygenated with tillage and carbon (straw) would be rapidly consumed. But quickly after the tillage, soil will settle and air will be pushed out and the soil would return to a state of collapsed pore space. Guess what that requires... more tillage.

If you had anaerobic conditions below the soil surface, there would be no straw at all because nothing would have grown. Shying away from a heavy residue is bad advice, and shows a misunderstanding of soil structure and C:N balance in the soil. Look no further than your typical bean field. Soybeans planted into heavy corn residue on the surface thrive compared to soybeans in heavily tilled soil. Less soil splashes up on the plant (which reduces disease), soil temps are moderated, moisture is better retained, and rhizobia feeds off the carbon enabling them to affix nodules to the roots of legumes.

Crops heavy in either carbon (corn, wheat, oats, sorghum) or nitrogen (beans, clover, peas, vetch) need to either be blended or alternated to maintain balance. You'll know quickly if you're out of balance, because that's when you need to break out the chemicals and diggers to rectify your imbalance.

This is why homeowners are constantly fighting clover in their grass, and plotters are fighting grass in their clover. The soil is trying to balance itself, and we're fighting against it.

https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1166766.pdf

Thank you for your response. Somewhere I read about a fellow asking how soon to plant after spraying. I have read that some spray and plant at the same time. What I posted is not my opinion, but is a statement from Monsanto. I will say that I am not a herbicide spray guy. I will spray liquid foliars this year.
I am no soil scientist and my plots on my sandy soil may prove that. However, I am making progress.
Thanks for your carbon nitrogen article.
My "conclusion" is that I read some inconsistencies in the Monsanto article, as I think that you do also. Monsanto does list some negatives to Roundup and residue. They said it, not some anti guy. I have read elsewhere about a positive response to Roundup in succession plants because of the phosphorous. Not enough to sway me.
I am more in tune with your post, with the exception of the favorable comment to Monsanto contributions.
I am going in the no till, min till direction with mowing. I am waiting for a response from one of Ray Archuleta's buddies on preparation for planting one of his "cocktail" mixes.
I think that this approach is more in line with your carbon nitrogen source.
FWIW, I would rather mow annual weeds than spray as I am of the opinion, and Monsanto stated it themselves that there are residual concerns.
I am trying to improve my soil health with covers, mowing, overseeding and rotations.

 

[MarkDarvin]

God only knows how much they had to put down per acre to see such a phenomenon. As weeds started becoming resistant, the amounts of roundup poured onto the soil was staggering. I wouldn't be shocked if the stuff just reactivated when it got wet and washed off the source material above ground.

 

[Bowman]

This is the response that I received from one of Ray Archuleta's buddies. Nothing earth shattering.

"It looks like you have the right tools to put in a successful plot. Unfortunately, without some aggressive Tillage broadcast seeding the first planting may not be very successful as there will be severe competition from any existing grass and weeds.

You will probably want to disc two or three times leaving a week between each discing for a weed flush to get the existing seed bank under control. Broadcast seeds after the last discing and use the cultipacker to have optimal seed to soil contact. Small seeded legume, Brassica and cereal grains will work well this way. With subsequent seedlings a light disc, broadcast and cultipacker should do the job as weeds will be in good control.

Late summer we would recommend a mix of oats, clovers and Brassica or our winter plot mix. This would over winter and be a good base for a summer plot next year."

i am planning on a diverse, multi-species mix for ground cover and roots. I have not yet even done anything yet in that location. I want to grow a centrally located plot. I think that I will have a lot of work to do.

As I write this, it is snowing again and temps will remain cold for the next 2 weeks with more snow. With all of this global warming going on, I will have to make a decision on if this location should be winter carryover or spring greenup. I am in mostly hardwoods and so far, I have very few tracks and no sightings of deer. I will consider rotations and uses of other plots. So far my brassica plantings have been hit early and I have grown no significant bulbs. About a month ago, it was warmer and bare ground. I had pulled the cameras already, but I had tracks and the alfalfa bales I put out as a test were all eaten. Now with over a foot of snow, the deer are gone again.

I would have thought that it would be warmer now and weather will be another consideration. My main plan is to build my sandy soil and keep the ground covered. To be continued...