dontknowanything
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No, I refuse to believe he could do that
No-till versus ploughing -- does increased stratification help?
- Thread starter Feldspar
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Feldspar
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Over thinking would be a fair charge if there obviously only positive effects from stratification. As I've shown above, there clearly is the potential for negative effects. Given positives and negatives, it isn't clear whether stratification is a good or bad thing and so some thinking is required. Plus I have never been known to overthink anything therefore it can't be the case (eta: beaten to it)!
Feldspar
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There is a positive story that could be told here about NT, which is that it does lead to higher C sequestration and SOM, and these meta-studies fail to pick up the underlying reality because of deficiencies in the way no-till research is conducted -- see Rolf Derpsch on this matter: http://www.sciencedirect.com/science/article/pii/S0167198713001992.
Taking that line, you could pick a paper like this, say that no-till is a great thing because it does do these good things mentioned above, and also that stratification is a good metric to use in determining how much of these good things has occured: http://www.sciencedirect.com/scienc...30c174c1e40776982a8f6ef3cb43483b3a28892d90a0d.
Nevertheless, to quote at length from the introduction in the paper directly above (sorry, couldn't be bothered to reformat),
Taking that line, you could pick a paper like this, say that no-till is a great thing because it does do these good things mentioned above, and also that stratification is a good metric to use in determining how much of these good things has occured: http://www.sciencedirect.com/scienc...30c174c1e40776982a8f6ef3cb43483b3a28892d90a0d.
Nevertheless, to quote at length from the introduction in the paper directly above (sorry, couldn't be bothered to reformat),
1. Introduction The term soil quality implies ‘‘the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation’’ (NRCS, 2008). Soil organic matter (SOM) strongly impacts soil quality, and interacts with soil chemical, physical and biological parameters, which determine plant growth. It is widely recognized that continuous NT farming leads to stratification of the SOM pool, with the highest accumulation in the surface layer (Dick, 1983; Rasmussen and Parton, 1994; Sa´, 1999; Franzluebbers, 2002; Dı´azZorita and Grove, 2002; Franzluebbers et al., 2007). In contrast, soils under plow tillage (PT) to 20 cm depth cause a uniform distribution of SOM (Franzluebbers, 2002; Dı´az-Zorita and Grove, 2002). The stratification of SOC pools with depths in undisturbed soil (i.e., natural vegetation) is a natural process governed by continuous input of C by litter at the soil surface and less input with soil depth (Prescott et al., 1995; Franzluebbers, 2002). This enrichment of the surface layer with SOM maintains soil quality by enhancing aggregation and facilitating aeration (Doran and Parkin, 1994; Franzluebbers et al., 2007). The conversion of natural vegetation to agricultural ecosystems based on PT degrades soil quality by mixing surface soil with subsoil and decreasing SOM stratification. Mechanical disturbance by PT disrupts aggregation, exposes SOM protected within the aggregates to microbial attack (Elliott, 1986), and exacerbates erosion-induced soil degradation (Lal, 1997). The stratification ratio (SR) of SOM can be used as an indicator of the soil quality under diverse tillage methods (Franzluebbers, 2002; Dı´az-Zorita and Grove, 2002; Franzluebbers et al., 2007). Franzluebbers (2002) defined SR as the ratio of parameter values in the soil surface with that at a lower depth, such as the bottom of the tillage layer. This lower depth is used to normalize the assessment and make valid comparisons among soils from different ecoregions or landscape positions with inherent differences in soil capability. Several studies have shown that SR ranges from 1.1 to 1.9 for CT and 2.1 to 4.1 for NT (Blevins et al., 1977; Blevins et al., 1983; Ismail et al., 1994; Dı´az-Zorita and Grove, 2002; Franzluebbers, 2002; Franzluebbers et al., 2007). The SR of SOC was proposed as an efficient indicator of soil quality (Franzluebbers, 2002; Dı´az-Zorita and Grove, 2002), and its increase can be related to the rate and amount of SOC sequestration (Franzluebbers, 2002; Moreno et al., 2006; Brye et al., 2006).
they have also just assumed that stratification is a good thing because they think it happens alongside higher SOC and SOM more generally, and they think that ploughing is damaging. If you accept Derpsch's argument, you say that it doesn't matter if stratification is good or bad because it comes necessarily with no-till and no-till is a good thing so stop worrying. If, on the other hand, you are more sceptical about no-till's link to higher SOM etc., then you can question whether stratification is inherently a good thing. I still don't know so will keep on digging.
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Feldspar
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- Essex, Cambs and Suffolk
Good quote: "“The sharpest minds often ruin their lives by overthinking the next step, while the dull win the race with eyes closed.”
SilliamWhale
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or simply put Ignorance is bliss
As for stratification - do you have any info on stratification of nutrients in grasslands as well - if the situation is similar then how big a problem is it and if its not similar ,why not?
Will Blackburn
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If there is a stratification problem then look at worms rather than steel as the solution.
Dan Powell
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- Shropshire
Is there a stratification of organic matter in grassland or is it well distributed thoughout the rooting zone ie organic matter being driven by root exudates rather than by surface litter/dung? If the latter is the case then would organic matter stratification in no till arable imply a lack of deep rooting crops in the rotation.?
Will Blackburn
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Worms take it underground, they do need a reasonable pH though. A characteristic of acidic grassland is a build of organic matter on the surface.
To trump Feldspar's dinner date with Liz Stockdale, I was discussing this issue with Ademir Calegari and Jay Fuhrer at breakfast the other day...they were a bit surprised that anyone would question the benefits of no-till, stratefied soil profiles or not. Of course they are used to dealing with farming in rather more brittle landscapes than we are used to in the UK, for them any disturbance can lead to massive erosion by wind or rain and increased SOM under no-till is more noticable, not least because exposed soil oxidises SOM quickly.
At the No-till conference I've just got back from, there was a big emphasis on getting deep rooting cover crops into the rotation (ideally with animals grazing them) and also having living roots in the ground all the time, where-ever possible. These practices help spread SOM through the profile.
At the No-till conference I've just got back from, there was a big emphasis on getting deep rooting cover crops into the rotation (ideally with animals grazing them) and also having living roots in the ground all the time, where-ever possible. These practices help spread SOM through the profile.
This isn't strictly about stratification, but the results Rick Haney has for Gabe Brown's soils are quite astonishing:
http://www.grazeonline.com/canweregeneratesoils
http://www.grazeonline.com/canweregeneratesoils
dontknowanything
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In other news, most of the 12 disciples were a bit surprised that anyone would question the benefits of Christianity
Funnily enough, I was talking to St Thomas the other day and he had great doubts
Louis Mc
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- Meath, Ireland
How can no-till be bad?
dontknowanything
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Poorer yields, increased NOx emissions, reduced carbon through lower biomass production etc etc
marco
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- tipperary, ireland
Thats poor or bad no-till your thinking of, i did that for a few years before i started cover cropping. its not fun and very stressfull.
SilliamWhale
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What did you have for breakfast?
Feldspar
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Louis, you're too intelligent to ask such an unimaginative question!
I agree with David, there are plenty of ways that it can be bad. For example, I'm willing to bet that the UK farmer with the highest 5 year yield average in any crop you care to pick is not a no-till farmer. You can say that they're only doing it by mining the soil, but if no-till generates such healthy soils, why do we not see the long term no-tillers performing best?
Some other negative effects, particularly NOx emissions, can be really quite insidious, and yet are totally invisible to the farmer wandering his fields.
This is one of the better overall studies of global no-till performance: http://www.sciencedirect.com/science/article/pii/S0378429015300228. You can see that in some crops you are taking reasonable yield hits in the early years especially. There are some crops that do not take a huge hit in certain climates, and also, which is for me the most encouraging aspect, is that you do see a trend towards better yields with time, although not to the point that they out-yield cultivated crops.
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I'm sorry, I'm with Louis in the dunces corner on this one. 2 obvious points need to be made here
1. All this talk about yield is so 20th Century. What we modern farmers are keen on is profit. If we are taking a yield hit of 4 to 7% that this paper talks about, then that is easily covered by vastly lower 'fixed' costs
2. These paired studies inevitably end up comparing chalk with cheese, as to keep the researchers happy each side by side plot has to be treated the same and, as we all know, no-tillers don't necessarily want to drill/fertilise/spray at the same time as their 'conventional' neighbours. So a compromise is reached, probably favouring the conventional, as that will be the expected way.
Of course no-till can be bad, but only when it's done wrong
Feldspar
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Thanks for engaging.
Addressing each point in turn. Firstly, on the yield question, I agree that profit is the ultimate guide of performance. Moreover, profit averaged out into the future is even more important for the farmer who intends to stick around. I agree that if your overall costs can be reduced by an amount equal or greater to the equivalent value of the yield loss under no-till then in that year no-till can be at least as profitable.
One point to make here though is about cropping intensity. Whilst you might be able to compete on profit with a crop within a certain year, if in order to achieve that you have to dramatically reduce your cropping intensity (which might be part of the reason for why SOC differences may not be that different between no-till and conventional), your averaged profit over a cycle might end up being less than a conventional system.
On the second point, I don't think it is the case that research between two different systems inevitably ends up comparing chalk and cheese. It may be the case that in some studies the comparison contains a certain degree of incommensurability. However, it isn't a rule that all comparison studies enforce the rule that the only thing that can be changed is the establishment method. Multi-variate analysis and other analytical techniques allow systems to be compared where supposedly best practice is being employed on both sides. This is particularly the case in research into long-term SOC levels -- here the systems can be more easily compared holistically.
I think it is unwarranted to assume that the way the research is conducted will naturally favour cultivation based systems. It's a sort of Trumpian thinking that the system is automatically biased against you. Inevitably there is a distribution of different qualities of no-till from "good" to "bad". But then there will be the same distribution within conventional systems. We all know that ploughing in silly wet conditions is going to cause more damage than ploughing in dry conditions. Therefore, you can equally argue that some comparison studies will have ploughing done badly, which will unfairly bias the result towards no-till. If you considered ploughing done well, maybe in a mixed farming system which incorporates organic manures, you might just find that it performs better than no-till done well.
Don't get me wrong, I am not strongly arguing that no-till systems are less profitable; however, I am arguing against a mindset which refuses to contemplate any possible downsides to one's favoured system. I do think, though, the evidence on carbon sequestration under no-till is shakier than a lot of no-till converts make out.