Marine Permaculture & Carbon Cycling – Project Drawdown

Website: Drawdown

Adding Carbon to Soils increases Microbial Nitrogen Use Efficiency

… and that in the short-term carbon through microbial form immobilizes already available N, potentially making less available for plants or loss through leaching.

The belief that adding high-carbon mulch locks up nitrogen may yet have some merit, not necessarily in the mulch, but in the microbes!

From Short-term carbon input increases microbial nitrogen demand, but not microbial nitrogen mining:

Although C input promoted microbial growth and N demand, we did not find indicators of increased N mobilization from SOM polymers, given that none of the soils showed a significant increase in protein depolymerization, and only one soil showed a significant increase in N-targeting enzymes. Instead, our findings suggest that microorganisms immobilized the already available N more efficiently, as indicated by decreased ammonification and inorganic N concentrations. Likewise, although N input stimulated ammonification, we found no significant effect on protein depolymerization. Although our findings do not rule out in general that higher plant-soil C allocation can promote microbial N mining, they suggest that such an effect can be counteracted, at least in the short term, by increased microbial N immobilization, further aggravating plant N limitation.