Saturday, 9 November 2013

Soil Monoliths

"Pedologists always have a trowel or knife to hand so that they can dig around in the ground, a magnifying glass to observe the fine structure, a flask of hydrochloric acid to determine the carbonate content of the soil, and a book of colour samples to determine the colour content of the soil according to the Munsell scale. Under each colour there is a small hole in the hard, grey card. You can wheedle a small lump of soil into the hole to compare the colour with that of the card. Perhaps the most important measurement is the texture, the grain size composition: how much sand, silt and clay the soil contains. Experience soil surveyors roll a small clump of soil into at sausage and stick it in to their mouths, chew it, ponder it for a while, and then pronounce the verdict: light loam, 15 per cent clay.

And then it starts, as there is always more than one pedologist around the pit at any one time. They take turns to jump in, pick at the wall and taste the soil: 'I think its heavy loam, 20 per cent clay.'. They will disagree about the depth of the humus layer and how the soil originated: has iron leached down from the lead-grey layer into the brown layer beneath it, or is it just humus, or have thin streaks of clay leached into it, and how and when did that happen? There are endless discussions on the basis of qualitative, subjective observations, where the lack of statistical evidence is compensated for by years of experience in hundreds of pits. Bullshit around the pit, that's what we call it.

Then its time to take samples. Brown, double-walled paper bags are filled with soil, at least one for each layer, and its up to the soil laboratory to decide who was right. Sometimes you push aluminium tins into the wall to make a microscopic section and, if its really worth it, you impregnate the whole wall with polyester lacquer, stick a strip of medical gauze to it, pull it off again with the layers of soil stuck to it and put it in a wooden frame to take to the laboratory. The soil museum at Wageningen is full of these soil monoliths."

Salomon Kroonenberg - Why Hell Stinks of Sulfur: Mythology and Geology of the Underworld

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