It's never good to start with an apology. I do. Unfortunately I do not have access to the full paper so my comments may be dealt with but I would appreciate any counter arguments to my suggestions. My interests are two fold:
1. Soil carbon depends on the rate of carbon addition less the rate of oxidation. A change of practice establishes a new equilibrium which is reached at progressively slower steps as it is approached. Rate of addition depends on crop and yield and in the UK at least, rate of addition is many times higher than 50 years ago. Rate of loss depends on temperature and moisture (both vary with soil type and location) as well as cultivation technique and conditions at the time of cultivation. Theory at least, would suggest that the impact would vary and could be large or small so any general statements require an enormous number of samples over many sites over many years. Is this correct and can we make general statements with confidence yet?
2. A key component in our temperate climate is water logging and nitrous oxide release from the nitrogen contained in the residues. Again depending on time of year and the factors above more residue added could result in more nitrous oxide release which may or may not result in more GHG release than gained through the carbon captured. I suspect nitrous oxide release is very dependent on time of year when the cultivation is carried out. Was the nitrous oxide release recorded? It is harder to measure but possibly more important. Theory would suggest nitrous oxide release would increase as the carbon equilibrium is reached and less carbon captured so the relationship might change. Was this found to be the case?