Dear all,
I want analyze soil samples with loss of ignition method.
I chose this method because it is simple, economical and environmentally friendly. These aspects are important because the number of samples I want to analyze is high. I did a preliminary bibliographic search but I got lost in the different configurations proposed.
In particular, many different soil preparation (soil sieved at 2 mm or crushed at 500 um), temperature (350, 375, 400 °C) and time (4, 8, 17 h) are presented.
Can give me some useful information to optimize and apply the best and most widespread analysis protocol?
I would suggest you take a look at the following book:
Soil science: Methods & applications D. L. Rowell
You might want to cross check with some opther method if you want to publish the results
Compare your results with those of others and find the % of deviation and decide.
In the US, most of us basically the method described by the Sparks document above but has been standardized as follows:
1. Use 1-2 mm ground samples.
2. Place about 10 g of the soil into a crucible and heat at 105 C for 2 hours to dry the sample.
3. After the sample in cool, accurately take the initial weight of the sample and then heat to 360 C for 2 hours after the temperature reaches 360 C.
4. Cool the samples ant then accurately weigh a second time to determine weight loss.
5. Calculate the weight loss as a percent of the weight at 105 C.
Note: If the soils contain gypsum, they need to be dried at 150 C rather than 105 C to account for water in the gypsum.
These values may not be exactly the same values as the Walkley-Black method. In order to correlate these values to the Walkley-Black method, a selection of your soils in the normal organic matter range that you will be working with should be run by the Walkley-Black method and by regression analysis determind the adjustment needed to correct the loss on ignition values to the Walkley-Black values.
This procedure is widely used by most routine soil testing labs in the US (It's pretty well standardized). Some people may use other temperatures and heating times for specific purposes but the procedure presented above is closely related to the wet oxidation method (Walkley-Black).
The comparison of pre-treatment methods and ignition temperatures for determining the Soil Organic Matter, go with this following reference....
doi/full/10.1080/00103624.2018.1474475
If your soils are calcareous or having alkalinity problem I do not suggest you to use this method. Because at high temperature significant portion of soil carbonate converted to oxide that cause exrta weight loss other than the organic matter. Be sure that your soil oven dry (105C for 24 h) before exposing high temperature.
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