We are learning as we go along and the latest research adds to the knowledge available when I wrote my blog on Soil Organic Matter and Climate Change.
The results from 15 years of monitoring at FiBL I have reported on recently and there is now further work, this time from a 47 year trial from INREA in France which shows that soil carbon storage and mineralisation rates are affected by carbon inputs rather than physical disturbance.
The results are somewhat different from the FiBL trials, that may be due to soil type, which has a major effect on sequestration potential and initial SOM levels; sequestration potential tails off as SOM increases. What these trials continue to show is the importance of maintaining high levels of organic matter inputs –whether that is in the form of green material – green manures and leys – or judicious use of manures and composts. Not only is that adding directly to stable soil organic matter, humus, but it is feeding soil life which enhances soil fertility and adds further to SOM through their eventual death and decomposition. Reducing cultivations may be important in some situations and for reducing damage to earthworms and mycorrhiza, but it is not the be all and end all that some maintain.
Interesting results from Rothamsted produced this week show that cattle grazing pastures rich in white clover produce half the amount of nitrous oxide than previously thought. This will require a major revision of the IPCC figures and bring us significantly closer to being able to show that forage based organic ruminants can be part of addressing the climate change impact of food and farming.