You first remove gravels by sieving the soil with 2mm sieve then follow the conventional determination of soil texture ..

You first remove gravels by sieving the soil with 2mm sieve then follow the conventional determination of soil texture ..

Dear Srivastava Sir,

Thank you very much for your valuable suggestions. As you have suggested similar comments I have found in various text books. Here my concern about the process of removing the gravels: which should be before taking the soil sample (i.e. 200 gm or 500 gm)  for the experiment (e.g. wet sieve analysis)  or over the retained sample on the 75 micron sieve during wet sieve analysis.

I have taken a 200 gm soil sample and wash in the 75 micron sieve. The retained sample in the 75 micron sieve have processed through mechanical sieve analysis and results are as follows

IS Sieve (mm)     Wt Retained (gm)          

4.75                       5.192

2                            7.359

1.18                       5.362

0.6                         10.29

0.425                     10.155

0.3                         4.046

0.15                        29.26

0.075                      13.681

Here I am not considering the first two rows belonging to IS Sieve 4.75 and 2 mm). Is this process correct ? or I would have to pass the soil sample thorough 2 mm sieve first to remove the gravels first and then take the soil sample for the further analysis.

Firstly avoid the gravels from whole soil by pass it through 2 mm sieve, then calculate the percentage of sand, silt, and clay. Finally, determine the soil texture using USDA soil texture triangle.

Regards

Dear Magboul Sulieman

Thanks for the valuable suggestions: but here problem is that I have already tested the large number of samples and the samples were selected (e.g. 200 gm) without passing any sieve. Therefore at present I have the data as given below:

IS Sieve (mm)     Wt Retained (gm)          

4.75                       5.192

2                            7.359

1.18                       5.362

0.6                         10.29

0.425                     10.155

0.3                         4.046

0.15                        29.26

0.075                      13.681

Now How should I find out the cumulative Percent weight retained?

By calculating  Percent weight retained [i.e. (Weight Retained / weight of the sample)*100], where weight of he sample is taken 200 gm and  then making a cumulative Percent weight retained from the Sieve from 1.18 mm (by neglecting wt. retained in 4.75 and 2 mm sieve) 

or

First removing the wt. retained in 4.75 and 2 mm sieve (here 12.551 gm) from total sample weight (here 200 gm) and obtaining the weight of sample (200-12.551=187.449 gm) . Further Percent weight retained estimating based on the sample weight 187.449 gm in the place of 200 gm.

Please provide the suggestions: 

Thank you

The first two totals would be gravels out of 200 gm soil taken. In effect you determine the quantity  of sand, silt and clay from 187.449 g as given by you in second option. USDA limits for sand are 0.005-2.0 mm,  0.005-0.002 for silt and < 0.002 for clay. This you get by hydrometer and looking to textural traingle determine its texture. If gravels constitute > 15% the texture may be qualified as gravelly....... 

@ Ghulappa,and @ Gurjeet = The USDA limits for sand, silt, and clay would be 2-0.05 mm, 0.05-0.002 mm, and

I really appreciate the answers here. But does anyone know the procedure to compute percentage of soil classes from textural traingle. well know one is classiication of soil using textural triangle.