Saturday, May 3, 2008

Scientists focus on making better soil to help with food concerns

Christian Science Monitor: ….Dirt remains, in certain ways, a puzzle: Despite its seeming simplicity, it is a complex system whose fertility arises from the interaction of myriad physical, biological, and chemical properties. Even the most advanced current research does not claim to be able to synthesize enough of it for use on a global scale.

….Because of all the things human beings do to it, a University of Washington geologist, David Montgomery, has calculated, the world today is losing soil 10 to 20 times faster than it is replenishing it. In some places it is happening much faster: northern China, sub-Saharan Africa, parts of the American West and Australia are already seeing large tracts of arable land disappear.

…Among the world's richer soils is terra preta, the "black earth" found in certain swaths of the Amazon basin. It is dark, loose and loamy, and unlike the pallid earth that characterizes most of the Amazon, it is strikingly fertile.

In the last few years, archaeologists have established something else intriguing about terra preta: it is man-made. It contains high concentrations of charcoal, along with organic matter such as manure and fish bones - essentially the household trash of a pre-Columbian society practicing a distinctive brand of slash-and-burn agriculture.

Researchers trying to replicate the fertility of terra preta have concluded that its secret is in the charcoal. Work by soil scientists like Laird, Johannes Lehmann of Cornell University, and Mingxin Guo of Delaware State University suggests that the benefits of supplementing soil with charcoal, which they call "biochar" to distinguish it from the fuel of backyard barbecues, could be dramatic, widespread, and durable. Biochar, they have found, enhances the retention of water and nutrients, decreases the need for fertilizer, encourages microbial growth, and allows more air to reach crop roots. It also breaks down at a far slower rate than traditional fertilizers and soil additives. Depending on how the charcoal is made and applied, estimates of its life span range from decades to millennia.

....Even its champions concede that there's plenty we need to learn about how to produce it on a mass scale. Researchers today are looking at how it might best be applied to the soil - in a dust, perhaps, or in pellets, or in a slurry mixed with manure. Two American companies, Eprida and BEST Energies, are working on bringing it to market.

Other scientists are looking at an even more ambitious project: making new soil from scratch. The challenge is to make truly synthetic soil that matches the stability and longevity of natural topsoil….

Terra preta is on the right. Photo by Bruno Glaser, Wikimedia Commons, under the terms of the GNU Free Documentation license, Version 1.2

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