Tuesday, 21 May 2013

I can't believe you'd kill me for a field of empty holes.

So, a trivia question first - from which film is the above a quote. And possibly more importantly why on earth did it stick in my mind from an otherwise rather unmemorable movie?

Anyway, we don't have a field of empty holes (can a hole be empty?) but a field of intact soil columns. Far more valuable than holes.

Today we set up our in situ gas monitoring kit and measured green house gas fluxes from (and into) our soils prior to adding grass and then earthworms. We need this initial measurements to see how varied the gas emissions are across our soil columns and to have a base line with which to compare emissions once our plants and earthworms are doing their stuff.

Hongling and Sylvia setting up the N2O (lower big box) and CH4 (upper, smaller box) samplers.
Connecting the tubes - the yellow box just in shot is an IRGA and measures CO2 flux. It contains a pump and, thanks to the tubing that Sylvia and Hongling are connecting draws the gases coming out of the soil through itself (to measure CO2) and the N2O and CH4 monitors.
So now measurements are in progress - you can see the measuring chamber of the IRGA sat in a column just in front of Sylvia's right foot.

  Here is a close up of the IRGA. Below the metal cap you can see the black bellows and below that a white chamber. When it is time to measure the gas emissions the white chamber moves down onto a grey collar (you can see one in the next column at the front of the picture) and the gas starts to accumulate in the chamber. The gas is pumped through the IRGA and other analysers and we measure rate of gas accumulation in the chamber, i.e. flux.

We also measure soil moisture content with a Theta probe (the grey cylinder) and temperature (the white cylinder) as these will impact on the rate of greenhouse gas emissions from the soil and vary over time.
Finally, here is a screen shot of our real time N2O gas flux measurements (the top line, the lower line is real time isotopic analysis of the N allowing us to determine the source of the N2O - nitrification or denitrification). Each peak corresponds to a separate measurement and the different peak heights show us that the soils in our columns are releasing N2O at different rates.