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

[Feldspar]

The one thing we know for sure is that no-till reduces the losses of organic matter. If you don't keep artificially aerating the soil to depth, you won't be stimulating the bacteria that feed on it and therefore releasing CO2 into the atmosphere.

The other thing is that organic matter is no use if it is down below the aerobic layer, however deep that is. Even in permanent grassland, fence stakes don't rot all the way down, they give a very good idea of how far the air is getting into the soil and so ploughing OM down below this level is pretty stupid.

In the days of horse drawn ploughs running at four of five inches in mid winter when the soil was too cold for any microbial activity to be going on anyway, probably wasn't a big deal, but today's deep summer and early autumn ploughing is a whole different ball game.

I don't think that we do know that for sure. Really I think the evidence is actually quite divided on this question.

 

[fudge]

I don't see that it's obvious that it's neither a good thing or a bad thing?

Well ok but why would it matter in a no till situation? There wouldn't be a thing you could do about the I'm being concentrated at the top.

 

[Feldspar]

Well ok but why would it matter in a no till situation? There wouldn't be a thing you could do about the I'm being concentrated at the top.

Not in a no-till situation, no, but you might be deciding whether or not to do some light cultivation. If reducing the amount of stratification right near the surface was a good thing, this might increase the attractiveness of such a light cultivation pass.

I am quite interested in the effects of soil aeration near the surface, its effect on soil temperature, and the knock-on effects on plant growth. My feeling from last spring was that unmoved soil was very slow to dry, which in turn made it very slow to warm, which again in turn made the plant growth much slower than more aerated, darker, warmer, cultivated soils. I feel that a shallow cultivation pass may help with easier spring crop establishment and faster growth (and potential more biomass and yield). If the decrease in stratification from cultivating a no-till soil is not a bad thing, and if it's not going to markedly reduce the overall SOM, then I don't have too much to worry about. If the reverse is true, then I do, hence the reason for this thread.

To back this thinking up, here's an extract from this paper, http://www.sciencedirect.com/science/article/pii/S0167880906001617:

... in no-till systems the soil heat flux is typically lower than in conventionally tilled fields, due to the insulating effects of surface residue (Shen and Tanner, 1990) and an albedo that is generally higher. In combination, these features tend to make no-till soils cooler than conventionally tilled soils, especially in the early part of the growing season (Johnson and Lowery, 1985; Drury et al., 2005; Fabrizzi et al., 2005). Soil temperature in turn is one of the key factors controlling root growth, with up to 5-fold differences in root growth over temperature ranges of 4–5 [degrees Celsius]. (Logsdon et al., 1987; Mackay and Barber, 1984).​

 

[fudge]

Personally on our soil type I wouldn't consider no till for spring cropping because autumn ploughed land dries far quicker in the spring. In other words it is far easier. Before you attempt shallow spring cultivation you must consider if it is dry enough. Cultivating heavier soil types when too wet is a no going to make for a very good seedbed. IMO this is far more important than slight variations in where the organic matter is.

 

[Feldspar]

Personally on our soil type I wouldn't consider no till for spring cropping because autumn ploughed land dries far quicker in the spring. In other words it is far easier. Before you attempt shallow spring cultivation you must consider if it is dry enough. Cultivating heavier soil types when too wet is a no going to make for a very good seedbed. IMO this is far more important than slight variations in where the organic matter is.

Sorry, should have been clearer. I meant doing a shallow cultivation pass in the autumn in dry conditions as we have done this year. Once or twice through with the Terrastar.

 

[dontknowanything]

The one thing we know for sure is that no-till reduces the losses of organic matter. If you don't keep artificially aerating the soil to depth, you won't be stimulating the bacteria that feed on it and therefore releasing CO2 into the atmosphere.

The other thing is that organic matter is no use if it is down below the aerobic layer, however deep that is. Even in permanent grassland, fence stakes don't rot all the way down, they give a very good idea of how far the air is getting into the soil and so ploughing OM down below this level is pretty stupid.

In the days of horse drawn ploughs running at four of five inches in mid winter when the soil was too cold for any microbial activity to be going on anyway, probably wasn't a big deal, but today's deep summer and early autumn ploughing is a whole different ball game.

I don't agree that SOM below the aerobic layer is useless. It may not stimulate biological activity, but it still has desirable physical properties such as increasing water holding capacity. This is of great importance to us, probably less to you.

 

[dontknowanything]

I don't think that we do know that for sure. Really I think the evidence is actually quite divided on this question.

Really? Even when starting from SOM levels above the equilibrium point, say grassland going into cropping?

 

[Feldspar]

Really? Even when starting from SOM levels above the equilibrium point, say grassland going into cropping?

Intuitively I'm very keen to agree with you, and there are certainly a lot of papers which would support such a position. I just think that on balance the picture is surprisingly mixed. Too late now, but I'll expand on this another day. In the meantime, the abstract of this paper nicely aligns with my current thinking on this: http://www.sciencedirect.com/scienc...2f0d0debb6f00f3d38e302ff6c36b08cb04e9002ecbee.

P.S. Have spent the last few hours trying to find enough material to be able to quantify the benefits of a better spray boom versus a worse one. Haven't done very well so far.

 

[Will Blackburn]

Not in a no-till situation, no, but you might be deciding whether or not to do some light cultivation. If reducing the amount of stratification right near the surface was a good thing, this might increase the attractiveness of such a light cultivation pass.

I am quite interested in the effects of soil aeration near the surface, its effect on soil temperature, and the knock-on effects on plant growth.

If you need to black the surface to improve soil temperatures then do it. I think trying to justify it from another angle is navel-gazing.

 

[More to life]

Very interesting,like so many things actual facts are hard to find.

 

[dontknowanything]

P.S. Have spent the last few hours trying to find enough material to be able to quantify the benefits of a better spray boom versus a worse one. Haven't done very well so far.

You've already shown how height effects drift

 

[dontknowanything]

Intuitively I'm very keen to agree with you, and there are certainly a lot of papers which would support such a position. I just think that on balance the picture is surprisingly mixed. Too late now, but I'll expand on this another day. In the meantime, the abstract of this paper nicely aligns with my current thinking on this: http://www.sciencedirect.com/scienc...2f0d0debb6f00f3d38e302ff6c36b08cb04e9002ecbee.

P.S. Have spent the last few hours trying to find enough material to be able to quantify the benefits of a better spray boom versus a worse one. Haven't done very well so far.

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

 

[Feldspar]

You've already shown how height effects drift

I'm trying to get a handle on whether you could claim that better boom control will give you x% increase in spray deposition which combined with how much we spend annual on pesticides would give a rough value to the extra boom control. Then add in more spraying days / less environmental pollution as extra factors.

There is some evidence that uneven deposition to due to yaw and roll is exacerbated with lower boom heights because there's less mixing of the spray jet pattern.

Found some interesting work on the amount of pesticide that evaporates off the leaf in the 24 hours after application. With something like prosulfocarb it can be up to 80% loss. Was thinking to myself whether in the summer whether spraying at night might provide benefits because the greatest loss is immediately after spraying.

 

[Richard III]

Why does No Till not increase soil carbon? It is very clear on farm that cultivations oxidise organic matter and that ULD drilling can oxidise that little that popup fertilizer is needed, this would suggest it should. Could it be that deep cultivations move some organic matter down far enough that it is not as vulnerable to microbial decomposition during the year, whereas No Till leaves it near the surface and so more vulnerable? This would fit with the massive greening effect I see on my crops that starts mid May and continues till senescence.

If this is true, possibly the worst system is going to be one that keeps the O.M. near the surface and moves it, i.e. scratch tillage. However the worst of all worlds is probably simply growing a poor crop and putting little O.M. back.

 

[dontknowanything]

Why does No Till not increase soil carbon? It is very clear on farm that cultivations oxidise organic matter and that ULD drilling can oxidise that little that popup fertilizer is needed, this would suggest it should.

I don't think that is clear at all actually. For instance, it could be that tillage oxidises the OM at the beginning, with the resulting N release all in one go, whereas no-till may have the same oxidisation, but spread over the season so you never notice it in the plants. At the risk of sounding patronising, it's very dangerous to draw conclusions from observations like this, especially when you know the answer you want to find.

However the worst of all worlds is probably simply growing a poor crop and putting little O.M. back.

I do agree with this; although the lab-heads will tell you that inorganic N destroys SOM, I think there is good evidence that it's outweighed by making more in the form of plant residue. I'll just drop this here again as I always do when the subject comes up, because I know @Feldspar loves it

Day 62 – Pasture rotations & SOM

 

[Hampton]

So this question has been bugging me for a while. I keep hearing recently, and I think I am correct that @martian is a proponent of this approach, that no-till is a vital way of sequestering carbon in the efforts to combat elevated atmospheric concentrations. Moreover, and perhaps more relevant to farming in the shorter term, is the claim that this extra SOC will dramatically improve the fertility (and therefore the productivity) of our soils.

There is only one problem with this, I think there's a good chance that no-till doesn't actually do the above. To get a really overview of the corpus of academic work on this area pretty much requires this to be your job, but having done a good few hours -- probably tens of hours -- reading around this subject, I come somewhat begrudgingly to hold this viewpoint.

There is a lot of erroneous information about SOM / SOC etc under plough and no-till systems. A lot of the errors come from incorrect sampling techniques. For example, sampling too shallowly and failing to correct for bulk density in the samples. Once those mistakes are corrected, the general picture shows surprisingly little difference between tillage and zero-tillage practices.

If it is the case, as a matter of fact, that there is no extra SOM due to zero-tillage, we can, I think, say with a good degree of certainty that zero-till causes a significant stratification of SOM which you do not see in plough based systems.

So, my question then is this: does the same amount of SOM concentrated near to the surface in a stratified way lead to a more fertile and productive soil? If so, should we be using SOM stratification as a more useful metric in assessing soil fertility rather than the error prone loss on ignition SOM tests?

Here's a paper which suggests that the answer to the last question should be "yes": http://www.sciencedirect.com/science/article/pii/S0167198702000181.

When I did my master thesis it involved taking 30 plants of wheat from 96 plots and assessing them. The results showed a significant relationship that a 10% extra infection was shown under certain conditions. My tutor was surprised as he thought it would be higher, but told me that I would probably have found a stronger correlation if I had taken less samples!
Showed me how easy it was for scientists to manipulate results to their agenda!

 

[More to life]

When I did my master thesis it involved taking 30 plants of wheat from 96 plots and assessing them. The results showed a significant relationship that a 10% extra infection was shown under certain conditions. My tutor was surprised as he thought it would be higher, but told me that I would probably have found a stronger correlation if I had taken less samples!
Showed me how easy it was for scientists to manipulate results to their agenda!

Commercial studies start with a conclusion then work backwards what is it they say on QI 10 % of every known fact is wrong!

 

[Feldspar]

When I did my master thesis it involved taking 30 plants of wheat from 96 plots and assessing them. The results showed a significant relationship that a 10% extra infection was shown under certain conditions. My tutor was surprised as he thought it would be higher, but told me that I would probably have found a stronger correlation if I had taken less samples!
Showed me how easy it was for scientists to manipulate results to their agenda!

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.

 

[Louis Mc]

Just go with your gut feel on this one @Feldspar .....science is corrupt

 

[Feldspar]

Just go with your gut feel on this one @Feldspar .....science is corrupt

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.