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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoPlainText>Dear AD<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Terra Preta soil in the Amazon is probably the result of at least 10,000 years of rotational slash-and-burn farming (on about a 7 year cycle) and it formed accidentally. It is well established that the fertility of the soil is much higher where the char is, and only a few feet away it is acidic and much less productive.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>OK, well and good. In the Amazon rain forest, there is nearly no nutrients in the soil because anything that can be taken up has been. The value is all above the ground, not buried in it. Is it possible that the char makes things <i>unavailable</i>? That the real reason it works is that it hold the nutrients away from the massive tree growth above?<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Apart from the obvious water-holding ability (which some soils do not have) is it possible the benefit comes from rotational slash-and-burn where the forest grows and invests in roots and litter, and the high-char soils grab and hold the fertility? Then some farmer comes along and plants a different set of crops that specialise in growing underground (yams, peanuts etc) and these plants are able to access the stored materials because they promote a different set of bacteria on their (different) roots.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>If the soil is in no need of additional water retention capability and is already exhausted and no retained fertiliser is in it, then there would be no benefit.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>>The fact that even the so called insoluble minerals like quartz and opal dissolve in water, suggests that charcoal buried in the soil might also be dissolved in water and absorbed by plants and microbes.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Carbon has quite strong electrical charges at the tips of its structures, right? That could induce mineral crystal breakdown together with a bacteria or two.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>>There are no records of molecular carbon being metabolized by living organisms, but this line of thinking needs to be followed up and investigated.<o:p></o:p></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black'>Correct. The fact that it seems to work well only in acidic soils might be a pointer. Acid + electrical charge. What does that give/liberate/stall/prevent/permit?<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black'>Regards<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'>Crispin<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p></div></body></html>