No-till versus ploughing -- does increased stratification help?

[Dan Powell]

So in other words, cover cropping is the way to go

So how much N should we apply to cover crops? I've been adding 30kg/ha as per Fred Thomas' talk but would more be better to get more biomass and more grazing? Certainly my grazing brassicas could take much more N and carry more sheep but then grazing would last longer and potentially cause more surface capping which could negatively impact the following crop or require a cultivation prior to drilling.

It's a complicated business.

 

[PSQ]

Just to throw something else into the mix: I've been doing a bit of work on 'VR Seed' derived from previous years NDVI's, and thinking about protocols to work with on my highly variable textured soils.

One of the side benefits that spring to mind is on the areas of less than average growth, which when corrected by increasing seed rate will increase the root , straw / chaf residues left behind, and therefore increase the amount of carbon sequestrated by the soil. Hopefully enough to eventually create a positive feedback loop, i.e. improve soil O.M. to the point that it helps correct the reason for poor establishment in the first place: poor soil texture.

 

[debe]

Exactly this. Even scientists who are well trained in statistics reliably underestimate the error involved in small sample sizes. I think agricultural research has a lot of problems with sample size because of the length of time it takes to get a trial to its endpoint. If I were to do a Nuffield project, I'd like to do it on this subject. With alternative facts, post-truth eras and Donald Trump, it seems like a rather apposite time too. Too often you see an LSD slapped onto the bottom of a slide with either little or no reference to it.

This is a very famous but short paper which basically explains and proves the above; it is well worth a read: http://pirate.shu.edu/~hovancjo/exp_read/tversky.htm.

I had dinner with Liz Stockdale the other week and apparently she is going to take a year off from her normal work to basically re-examine statistics within agriculture. I think, but may have misunderstood, that randomised control trials are seen as the gold standard (see work by Nancy Cartwright on this, even though it's more within the public policy realm), but she thinks there are better ways of acquiring knowledge.

Agriculture, like engineering is always going to be fraught with inaccuracy when it comes to scientific research. There are far too many variables and assumptions to achieve the same rigour as you can in a lab.

Surely the answer to your autumn cultivation is to carry on doing it until you find a better solution, as has already been said there is nothing worse for building (or maintaining) organic matter than a poor crop!

 

[Feldspar]

Agriculture, like engineering is always going to be fraught with inaccuracy when it comes to scientific research. There are far too many variables and assumptions to achieve the same rigour as you can in a lab.

Surely the answer to your autumn cultivation is to carry on doing it until you find a better solution, as has already been said there is nothing worse for building (or maintaining) organic matter than a poor crop!

That's the current strategy. Will continue to leave some uncultivated areas to investigate.

 

[dontknowanything]

No, it isn't. There are corrupting influences abroad at the moment, but correct response is to maintain a steady course rather than abandoning ship.

Quite. These problems with bias are not a new phenomenon, they have existed (I'm sure) as long as humankind. Obviously science has 'worked' in that time, even though it is not perfect, otherwise we'd all still be living in caves.

 

[dontknowanything]

So how much N should we apply to cover crops? I've been adding 30kg/ha as per Fred Thomas' talk but would more be better to get more biomass and more grazing? Certainly my grazing brassicas could take much more N and carry more sheep but then grazing would last longer and potentially cause more surface capping which could negatively impact the following crop or require a cultivation prior to drilling.

It's a complicated business.

I'm going with a nice round number for that, in fact it's the roundest number there is.

I feel vindicated by NIAB trial work showing less root mass in cover crops that have had artificial fertiliser applied.

 

[Dan Powell]

I'm going with a nice round number for that, in fact it's the roundest number there is.

I feel vindicated by NIAB trial work showing less root mass in cover crops that have had artificial fertiliser applied.

Yes that would make sense in a no grazing situation. I'm trying to find the optimum compromise between soil structure benefits and extra £££ from grazing.

 

[dontknowanything]

Yes that would make sense in a no grazing situation. I'm trying to find the optimum compromise between soil structure benefits and extra £££ from grazing.

When I trialled 30kg I got 21% more above ground DM. Which came absolutely nowhere near covering the cost of the fert from extra grazing. Careful that you're not just buying LWG for more than it's worth.

 

[Ruston3w]

When I trialled 30kg I got 21% more above ground DM. Which came absolutely nowhere near covering the cost of the fert from extra grazing. Careful that you're not just buying LWG for more than it's worth.

Do you value the added growth in terms of weed suppression.....every time I get mean and skip top-dressing radish I end up with a mass of nettle and amg on the poorest bits, a good start for cc and no problem?

 

[SilliamWhale]

Quite. These problems with bias are not a new phenomenon, they have existed (I'm sure) as long as humankind. Obviously science has 'worked' in that time, even though it is not perfect, otherwise we'd all still be living in caves.

But we were out of caves before science was invented!

 

[dontknowanything]

Do you value the added growth in terms of weed suppression.....every time I get mean and skip top-dressing radish I end up with a mass of nettle and amg on the poorest bits, a good start for cc and no problem?

Weed suppression is a negative if you're grazing the covers

 

[dontknowanything]

But we were out of caves before science was invented!

Depends on your definition of science.

Trial and error?

 

[Feldspar]

So to further my original question, and to tie into @dontknowanything's questions in his Nuffield, IIRC (although maybe it was fertility -- sure I'll be enlightened), about how to define soil quality, it would seem that these authors think that stratification is a good indicator of soil quality: http://www.sciencedirect.com/science/article/pii/S0167198702000181.

I'm not sure, however, whether stratification being a good indicator of soil quality necessarily means that stratification in and of itself is a positive thing.

 

[SilliamWhale]

Depends on your definition of science.

Trial and error?

Roger Bacon

 

[Feldspar]

OK, here's something a little more concrete. We know that in no-till soils that P becomes highly stratified. It is claimed that P losses from run-off are not an issue in no-till systems. I haven't read the full paper yet, but this study would appear to show that cultivation to depth has actually reduced P losses from run-off as a direct result of decreasing P stratification. Note, however, the caveat at the end of the abstract.

https://dl.sciencesocieties.org/publications/jeq/abstracts/32/4/1375

 

[dontknowanything]

Note, however, the caveat at the end of the abstract.

"Please view the pdf by using the Full Text (PDF) link under 'View' to the left."

?

 

[Feldspar]

" Please view the pdf by using the Full Text (PDF) link under 'View' to the left."

?

No, I mean this: "... as long as plowing-induced erosion is minimized." Some would say that this is unlikely to occur. Nevertheless, it appears to have occurred during the trials in this research.

 

[dontknowanything]

No, I mean this: "... as long as plowing-induced erosion is minimized." Some would say that this is unlikely to occur. Nevertheless, it appears to have occurred during the trials in this research.

Some people I enjoy winding up more than others. You're one of them, thanks.

 

[Feldspar]

Some people I enjoy winding up more than others. You're one of them, thanks.

Git.

 

[Dan Powell]

More organic matter at the surface leads to better surface tilth leads to easier establishment of crops.

Also better soil function e.g. infiltration.

I think you may be over thinking this.