I would like to know if there's a way to ensure every sample has the same initial conditions when performing soil experiments. The samples are going to be enclosed in containers of 13 cm height and 18 cm width.

Is there a soil sieving and packing procedure to ensure equal moisture distribution?

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    The sampling technique will depend to some extent on what you are testing for and how you will be testing it. Since soil moisture can vary dramatically from location to location, you typically have to dry the samples prior to doing any chemical analysis. Can you tell us more about what you are studying? Also, this might help: agrienergy.net/docs/lab-information/soil-sampling.pdf – That Idiot Sep 30 '16 at 12:07
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    Yes, more information please. It almost appears you have two questions: 1. Initial conditions - can you describe what initial conditions you want to control? 2. Moisture control. Or did you mean moisture control when you said initial conditions? – Srihari Yamanoor Sep 30 '16 at 18:04
  • I'm currently working on my postgrad project, which involves electronics and agriculture. I'm trying to see the effects of moisture content on the electrical conductivity of the soil. I'm using electrical impedance tomography for doing this.I have a pot with two rings of electrodes, one on the upper level & one at the lower level. I measured the moisture content of several 100gr samples of soil. and upon mixing and sieving I took some electrical measurements. Some of the pots had a somewhat homegenous conductivity, while others had a lower conductivity on the upper level and high at the lower. – DCrown Oct 2 '16 at 12:16
  • By Initial conditions, I mean having almost the same moisture content across all of the soil. I think that would allow me to say, Ok I have this pots with soil and every one of them have the same water content, and I could potentially say that my experiment is repeatable. – DCrown Oct 2 '16 at 12:23

This is very interesting. First, there must be some discussion about this in the literature about soil moisture probes since they basically conductivity as a function of soil moisture. Second, I think that unless you have a reason to test soil just collected from the ground, you'd need to "treat" all the samples prior to testing.

Since you don't specify any limits on the initial conditions, I suggest you might try starting by saturating the samples and then taking readings as they drain to field capacity and dry further. If you kept the samples in a temp and humidity controlled room (or container), the process would be repeatable.

The one "problem" I see with my suggestion is that the initial quantity of moisture in the soil at saturation will differ based on soil characteristics. However saturation and field capacity are soil-relevant properties, so this might actually be a benefit.

The only other way I can think of is to oven dry each of the samples, then add a measured volume or mass of water to each sample. Then you could mix the sample by shaking in a larger container for a specific amount of time. Basically - as long as you define the steps you take to make your samples, it should be repeatable.

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