BREAKTHROUGH WITH SCIENTISTS

Flux and soil variability are thrown in our faces whenever we ask for trading units of soil carbon. But one important US scientist has broken ranks with his colleagues to argue for sanity to prevail: "It is often pointed out that soils have a large amount of variability, but with knowledge of soil sciences and landscapes, variability can be described and sampling protocols can be developed to deal with this," writes Dr John Kimble in a paper published this year*. "One reason I feel people say that soils vary and SOC cannot be measured is that we soil scientists focus on showing variability, not on showing what we know about the variability. In soils we can go to a 100m2 field and sample every square meter and look at the differences we find. But if you sample every tree in a large area you would see a similar variability." Dr Kimble works for the US Department of Agriculture, National Resources Conservation Service, National Soil Survey Centre, Lincoln, Nebraska. "We too often focus on this [variability], worry about laboratory precision and field variation and do not look at the real world where most things are based on averages and estimated data. We tend to focus on finding variation and not on using our knowledge of soil science to describe what we know. All systems vary, but in soils we focus on a level of precision and accuracy that may not have any relevance to the real world because we can take so many samples and look at the variation." We need a half dozen more like this.

*Kimble, J., "Advances In Models To Measure Soil Carbon: Can Soil Carbon Really Be Measured?", in Lal, R., Cerri, C., Bernoux, M., Etchevers, J., and Cerri, E., eds., Carbon Sequestration in Soils in Latin America, Food Products Press, Birmingham, NY, 2006