@Ahmed Abd El-Gawad, Can you please provide the reference (perhaps a citing article) for this method? I do like the way it is measured.

Please, follow the attached file

@Ahmed Abd El-Gawad, Can you please provide the reference (perhaps a citing article) for this method? I do like the way it is measured.

This was very helpful @Ahmed Abd El-Gawad. Like @Raghuprakash, I would also like to know how to cite this procedure.

Measuring soil water holding capacity: Saturate soil with water in glass funnel. Allow the soil for free drainage for 48 hours. Cover the pot surface with plastic to prevent evaporation. Make some holes in the plastic to maintain atmospheric pressure on the soil surface. After 48 hours take the wieght of the soil again.

Water holding capacity = (Weight of saturated-drained soil (48h) - Weight of dry soil)/Weight of dry soil

This gives you 100% water hodling capacity (total).

Once total water holding capacity is known, you can calculate the 55% of it.

Lets say WHC = X g/kg dry soil

55% WHC = X x 55/100 g

Add this amount of water to dry soil and you will get 55 % of water holding capacity.

Follow this link

https://www.agvise.com/educational-articles/water-holding-capacity/

Greeting

Raghuprakash Kastoori Ramamurthy & Melanie Mullin here are some references related to Ahmed M. Abd-ElGawad method

Noggle, G. R., & Wynd, F. L. (1941). THE DETERMINATION OF SELECTED CHEMICAL CHARACTERISTICS OF SOIL WHICH AFFECT THE GROWTH AND COMPOSITION OF PLANTS. Plant Physiology, 16(1), 39–60.

Pramer, D., & Schmidt, E. L. (1964). Experimental soil microbiology. Soil Science, 98(3), 211.

Pramer, D. & E. L. Schmidt (1964) Experimental Soil Microbiology, 106 pages. Minneapolis, Minnesota, Burgess Publishing Company.

Childers, G. W. (1996). Bioremediation protocol for small scale oil spills in Louisiana marshes. Louisiana Oil Spill Coordinators Office/Office of the Governor Louisiana Oil Spill Research and Development Program OSRADP Technical Report Series 95004.

It appears that some of the above methods measure the amount of water that a volume of soil can hold and other methods address the "adhering" or water retention properties of a type of soil.

Peter D'Aiuto could you please explain the difference? I am a non-soil expert who just needs a reliable, simple method to determine the WHC of soil - any advice would be much appreciated!

Hi Karen,

I'm not a soil expert either : ) When I use the terms "adhering" or "water retention" I think of the ability of a type of soil to stay moist and drain slowly. This will be a reflection of the "water adhering" properties of a soil or the ability of the adhering material to attract the charged parts of a water molecule and the allowance of hydrogen bonding between water molecules in the tiny spaces of a soil. A pot filled with coarse sand will drain quickly and almost entirely, but a pot filled with sponges or peat moss will drain slowly and retain water. This has nothing to do with the volume of water the different materials can hold. It reflects the materials water adhering properties and the bonding amongst water molecules in that material.

I have used the method quoted with some success for OECD artificial soil and Kettering loam - however when I have tried it with Lufa 2.2 soil the substrate simply does not absorb the water. After 3 weeks sitting in the tray of water, the soil is still completely bone dry (filter paper is saturated).

Has anyone used this method on Lufa 2.2 or noticed similar issues with other soil types? I am at a complete loss as to why this substrate does not absorb the water through the filter paper yet others do - could it be related to clay content perhaps?