What are you doing with that soil in the kitchen?

At the age of eleven, I failed an exam called the 11+.  Passing it would have got me a place at the grammar school, which in turn might have led me directly to university.  As it was, I was placed in a secondary modern school.  The principal weakness of these schools was lack of aspiration, however, with hindsight, I realise the some of the teaching excellent and that I have reason to be grateful to at least three teachers.  Four years after leaving school at fifteen, I did secure a place at university to study engineering having passed some of the intervening four years as a merchant seaman (where I was England's most incompetent sailor) and as a shot blaster and painter.  Without the efforts of Mr. Wilson, Mr. Henschel and Mr. Stevenson, life could have been rather dull.

Mr. Wilson did not give me a love of maths, but he did provide a good foundation which later helped get into technical college to study for an Ordinary National Diploma.  In the 1960's many maths teachers had served in the Royal Artillery during the war, so in  addition to geometry, algebra and basics of calculus we were also taught some ballistics.  Mr. Henschel and Mr. Stevenson were both science teachers, Mr. Henschel retired in my fourth year and was replaced by Mr. Stevenson.  They were both good, but a little different.   Mr. Henschel taught in a methodical way which was not boring, I can remember many of his lessons including Hooke's Law, Ohm's Law, specific gravity, series and parallel circuits, make and brake mechanisms and much else.  With hindsight, I realise he was also quite wise, describing me as "sea lawyer" which is sadly true and an observation of which I should have taken more notice.  Mr. Stevenson was also good at "labs", but probably because he taught me in fifth form when young people should be open to ideas, he posed a few wider questions.  I remember asking a question about photosynthesis and how plants responded to different colour light, he suggested that I answer this myself by doing an experiment, I deeply regret not doing so.

For the past couple of years, sometime around sunset on Sunday afternoons I have been taking soil temperature measurements in my back yard.  The original reason for doing this was an attempt to work out when to sow seeds, in the way of these things, no obvious answer presented itself,  What was instructive was a few random measurements during the day which showed that there was considerable diurnal variation which creates a thermally turbulent environment for germinating seeds.  I appreciate that I could learned this in a book as I know this to be common knowledge amongst better gardeners than me, but one of the themes of this blog is how do you learn about stuff.

It was whilst poking a thermistor down a hole and hoping not to have to explain this bizarre activity to passers by, I remembered an experiment I had performed at school.  The objective was to measure the water and organic content of soil.  The method involved two steps, the first was warming a sample of soil to around 100 deg. C so that the water evaporated leaving dry soil.  In the second step, the sample was exposed to a bunsen burner and heated until it glowed a dull red after which it was assumed that all the organic matter had burned off.  At each stage the soil was weighed.  I adapted this process to utilise the facilities afforded by the kitchen scales and the living room fire.  It was my wife who posed the question which is the title of this post.

Approximately 200 gm of soil was placed in a an empty tin from which the label and remaining dog food had been removed.  In the morning, the previous evening's fire has burned out, but the ashes are still warm, so the tin is place amongst them until it is time to relight the fire in the evening.  At this point the soil is dry.  For the next stage, the coals are placed around the tin and the fire list as normal, the next morning when it has cooled the tin is weighed.

I'm hoping to create a time series of the water content measurements, as the winter recedes, it should be possible to place the tin in the sunshine which will cause it to dry, albeit at a slower rate than in the cooling ashes.

For a sample taken on 28-Dec-2014, the water content was 26.3% and the organic content 4.2%, the accuracy of these measurements is uncertain.

This is a long answer to a short question.