Friday, August 31, 2012
Grassland Biochar Surprise
The surprise here is that grassland soils retain elemental carbon or close enough equivalent to forty percent of total organic carbon in the grassland soils of the USA. That is very good news. Recall however that these original grasslands held many times as much carbon as grasslands than they do at present. Thus the terra preta effect is also a result of natural concentration caused by the conversion to annual cropping.
The take home though is that many other soils will retain residual carbon in this form and we need to measure for it.
In fact, it may well be a key fertility determinant that has to date been overlooked.
In time, I anticipate all working soils will be augmented on a regular basis with the direct intent of optimizing fertility in general and outright eliminating any need for chemical augmentation whatsoever.
I have also pointed out that char allows us to manufacture soils anywhere we can find water or produce atmospheric water.
Abundant and Stable Char Residues in Soils: Implications for Soil Fertility and Carbon Sequestration
Large-scale soil application of biochar may enhance soil fertility, increasing crop production for the growing human population, while also sequestering atmospheric carbon. But reaching these beneficial outcomes requires an understanding of the relationships among biochar’s structure, stability, and contribution to soil fertility. Using quantitative 13C nuclear magnetic resonance (NMR) spectroscopy, we show that Terra Preta soils (fertile anthropogenic dark earths in Amazonia that were enriched with char >800 years ago) consist predominantly of char residues composed of 6 fused aromatic rings substituted by COO– groups that significantly increase the soils’ cation-exchange capacity and thus the retention of plant nutrients. We also show that highly productive, grassland-derived soils in the U.S. (Mollisols) contain char (generated by presettlement fires) that is structurally comparable to char in the Terra Preta soils and much more abundant than previously thought ( 40–50% of organic C). Our findings indicate that these oxidized char residues represent a particularly stable, abundant, and fertility-enhancing form of soil organic matter.
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