Feldspar
Member
- Location
- Essex, Cambs and Suffolk
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.
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.