Friends:

2-mm sieved soil is prefered in analysis because:

1. It includes all primary soil particles, and

2. It excludes bigger soil aggregates wherein some elements/nutrients/variables may be physically protected, and may not be extracted in short analytical procedures, under-estimating therby the values/status of the nutrient of interest.

     2-mm sieve therefoere appears the most logical choice.

In soil organic C analysis, however, 0.5 mm or 0.15 mm sieved soils are usually recomened these days. I have tetsed it in my lab too, but didn't find any statistically significant difference in SOC values of these two soils (2mm Vs 0.5mm). 

Thanks.

Hi Benedict!

Well, as a matter of fact we are using also 4 mm sieved soil. The main idea is to remove some particles, roots, stones, to make finally quite homogenic samples. It is obvious that soil is very heterogenic matrix, but by the use of 2 or 4 mm sieved soil we can get some more homogenic and still representative soil samples. You can check it by using not sieved and sieved soil for Your studies, I assure You that You will get extremely big SD from unsieved soil in comparison with sieved soil.

Greetings,

Bartek

It sieved with 2 mm mesh due to soil agregatte structure. Some researchers are studying in soils sieved with 4 mm mesh. But 2 mm  sieved soil is the best suitable to use in soil analysis rather than 4 mm

bendict

may i know what tests you have carried out by sieving the soil through 2mm

The tests like soil pH, salinity are require to be carried out on soil samples sieved through 425 Micron

Dear all,

Many thanks to you for your wonderful contributions. @ Prakash, l did pH, EC, available P, K Mg on 2 mm and N on 4mm sieved soil.

I think because the particles  more than 2 mm size  will not cosidered as a soil because the larger soil particle is clay which is 2 mm in size...

We are forgoting about something crucial here - type of soil. The question is with what kind of a soil we are working? there is big difference between mineral soil and organic layer of soil (humus layer). In my opinion, 4mm for organic is enough, maybe for mineral 2mm is better. Unfortunately we have to keep an eye on the soil type.

We usually use 2 mm sieve because 2mm and smaller soil particles considered as agricultural soil. More than 2 mm particles are not known as the term soil in agriculture science. Therefore, we use 2 mm sieve to obtain a useful agricultural soil from soil samples.

Hi,

This is the standard size according to the Norma ISO 11464. (1994). Soil Quality – Pretreatment of samples for physico-chemical analysis. International Organization for Standardization.Geneva, Switzerland. 9 p.

but I don't know who and why 2 mm was defined .

Friends:

2-mm sieved soil is prefered in analysis because:

1. It includes all primary soil particles, and

2. It excludes bigger soil aggregates wherein some elements/nutrients/variables may be physically protected, and may not be extracted in short analytical procedures, under-estimating therby the values/status of the nutrient of interest.

     2-mm sieve therefoere appears the most logical choice.

In soil organic C analysis, however, 0.5 mm or 0.15 mm sieved soils are usually recomened these days. I have tetsed it in my lab too, but didn't find any statistically significant difference in SOC values of these two soils (2mm Vs 0.5mm). 

Thanks.

We all know that soil horizons are defined by  their texture, and 2 mm (coarse sand)   is the maximum size that can be reach by a particle in the texture triangle.

Three parts to this answer:

1- The fine earth fraction of the sample (less than 2 mm) is where the vast majority of the reactive surfaces in soil are found. Rocks not very reactive. Measure amount of rocks, measure soil properties in fine earth fraction, you can calculate the total soil profile properties.

2 - You have to determine whats soil and what rock, in the US large than 2mm is rock less than 2mm is soil

3 - Historicaly speaking air dried, ground, fine eath fractions are used for most standard methods of soil analysis. Referance your test to USDA ( http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1253872.pdf) or SSSA Methods of soil analysis  ( ISBN-10: 0891188258 | ISBN-13: 978-0891188254 )

That question is not specific enough. However, I will give an equally unspecific answer. Size separates greater than 2 mm in effective diameter are less influential when considering many agronomist processes.

Thanks a lot for all your contributions.