It is well known that when addign biochar, soil TC will increase. Ideally, assuming the TC contents of soil and biochar are a% and b%, respectively. Now if we added biochar at 3% (mass ratio) to soils. The ideal TC contents (X) should be the solution of a%+b%*3%=(1+3%)X? But we found after adding biochar, TC of soils usually is much lower than the estimated X. Well after adding there may be C loss via gas loss. How do you think? Did anyone ever check your measurement?
The balance of Photosynthesis to Respiration determines the long term loss stability or gain of soil organic matter.
While biochar does not degrade rapidly the effect of its liming effect and improvement of physical aeration with stimulate respiration of organic matter.
This stimulation of respiration is probably the reason that expected carbon increase is not as high as expected.
Some crops are highly productive in terms of photosynthesis but they do not conserve soil organic matter. Plants which are both highly productive and also maintain a lower respiration of plant residues will build soil organic matter.
I agree with Paul, If the soil was strongly acidic respiration might increase if the biochar increased the pH to a more favorable level. However, it's also likely that the act of incorporation may have caused a large C-loss through increased respiration. The question then relates to having a well-matched control treatment.
Can you test the respiration hypothesis? Paul.
Thanks for your comments. I agree with you that the loss of carbon can be due to co2 emission. We actually measured co2 flux but the gas loss did not equal the difference between the ideal X and the measured TC (not fit mass balance law). Just want to see more data from other labs. Btw, our experiment is lab incubation.
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