Water Holding Capacity (WHC) is the maximum value of soil water content. It is could be present as v/v (percent of volume) either w/w (percent of weight). Soil water holding capacity is the soil moisture content that will remain in soil after water drained off the large pores.

http://enoviti-hanumangirl.blogspot.com/2017/12/in-search-of-wine-quality-soil-and_18.html

http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447039&topicorder=6

Interest

@ Hassan, Pore volume = Total volume - material volume (It is the direct method of measurement). If you want to measure by optical methods, then it is the area of the material versus the area of the pores visible under microscope. Water holding capacity is already well discussed by Dr. Rakesh Kumar.

Pore volume (Vv)/ Total volume (Vt) = Porosity. If you know porosity [1 -(BD/PD)] (v/v) and total volume (Vt) can calculate pore volume (Vv).

Soil water holding capacity is the soil moisture content that will remain in soil after water drained off the large pores. It is generally done by Keen Raczkowski box (g/g or v/v).

The value you got is erroneous as in your estimation retention of water in filter paper used should be deducted. again, due to gravity the water from meso pores is also drained. But it should be considered for maximum water holding capacity.

Hence, Porosity> water holding capacity> field moisture capacity

Thank You all.

What I have understood is that to measure pore volume, I should set up the following experiment.

Take a known volume of soil and place it in a beaker. e.g (50 ml mark)

Then add water in that until the water hits the 50 ml mark,( i.e) saturate the soil.

Record the volume of water add. this is the pore volume of the soil?

finally porosity can be calculated from the formula =

porosity = Vol of water / (vol of Soil + vol of water)

this is mentioned in the method # 3 in the following site

https://www.wikihow.com/Calculate-Porosity

Please guide me whether it is correct method?

Add weighed soil (20 g) in to measuring cylinder and pack it sufficiently by adding small quantity of soil at a time (Ensure no air gaps).

Note down the volume of soil.

Pour 50 ml of water though pipette.

Wait for 30 minutes and note down the volume of soil + water in the measuring cylinder.

Total volume of soil + water should be 70 ml.

Final volume of soil + water is after 30 minutes----- (may be 60 to 65 ml)

The difference between initial and final volume will give porosity for 20 g of soil.

Convert to 100 g (multiply by 5) will give % of porosity.