HI Noha

Everybody is right in his advise.

Water holding capacity is easy to calculate. If no information about the soil you are studying then you have to get samples or otherwise use reference to use values available in similar soils.

Soil variability is very common to see in soils and rarely to find homogeneous soil. But some areas have more variability than others.

Water holding capacity can be determined by measuring soil moisture at Filed capacity and at Permanent Welting Point. The difference between those two soil moisture values is the water holding capacity.

Usually a soil water characteristic curve is developed for the soil to determine its water holding capacity.

Soil water characteristic curve is determined usually using pressure plate. If not available, then soil texture can be used to find the curve for similar soil from references.

Wish you the best

Burhan

From my perspective... If you cannot take samples, embed the relative humidity sensors in your prototype and interface it with any programming interfaces to control. For instance, the NI LabVIEW is easier to interface through DAQ assisted Application programming interface.

what is NI LabVIEW ?? i think it isn't available to me.

I think it will be very difficult, the study area is very wide

Dear Noha

I am not aware of the amount of information available in Egypt but a good solution to your problem will be to use land cover maps of the area of interest and interpret them through a GIS software.

What you will need are gps coordinates of the study area, the soil associations, the geology of the area, the domain soils, the association of these soils and the land use properties. This will help you to finally assign a drainage capacity for each soil type. It is possible that the water holding capacity that you are looking fro is already recorder for your area.

For example:

Site X is 1. shallow loam over chalk,2. Chalk and chalky drift, Shallow well drained calcareous sandy and coarse loamy soils over chalk or chalk rubble, 3. Some similar deeper sandy soils, often in an intricate striped pattern, 4.Slight risk of water erosion, 5. Cereals, peas, beans and sugar beet: some short term grassland.

Sorry that I can not help more but I hope that this will at least help you to start from a point!

Good luck

Hello, frankly i see that your problem is easy to solve because in Egypt is easy to find soils information, specially from the soils of the Delta. Apart from this, you can directly carry out your own measures with a pressure chamber to determine the characteristic curve.

@Yiorgos Gadanakis , E. Misle

thaks for your help

'afwan. And Noha, if you need just a general approach, Saxton et al., 1986 published a work with many regressions so that they built a nice way to got hydraulic properties of soil from texture. I have their paper and the old website where this can be used as html app. But in a simple search i found that today you can see the same in other websites like this: http://www.pedosphere.ca/resources/texture/triangle_us.cfm?210,89

I don't recommend to use this procedure with soils like andisols but you don't have volcanic soils.

You may take from literature based on properties of soils (might not be exact but crude). The best way to get some representative undisturbed samples and us ethe pressure plate apparatus to measure it.

If the region has an agricultural history, the soil profile in terms of porosity can be inferred by the nature of crops that thrived or thrives in the area.

There are many pedotransfer functions to do this. You will need psd and bulk density to estimate water holding. You can check soil maps of the region they may provide water holding capacity information. If you chose to estimate it on your own, please read this first. - Minasny B, McBratney AB, Bristow KL (1999) Comparison of different approaches to the

development of pedotransfer functions for water-retention curves. Geoderma 93, 225–253.

This material could be useful. Pls find attached.

You could check out this abstract too:

Predicting and mapping soil available water capacity in Korea [PeerJ

Suk Young Hong, Budiman Minasny , Kyung Hwa Han, Yihyun Kim, Kyungdo Lee

https://peerj.com/articles/71/ ]

HI Noha

Everybody is right in his advise.

Water holding capacity is easy to calculate. If no information about the soil you are studying then you have to get samples or otherwise use reference to use values available in similar soils.

Soil variability is very common to see in soils and rarely to find homogeneous soil. But some areas have more variability than others.

Water holding capacity can be determined by measuring soil moisture at Filed capacity and at Permanent Welting Point. The difference between those two soil moisture values is the water holding capacity.

Usually a soil water characteristic curve is developed for the soil to determine its water holding capacity.

Soil water characteristic curve is determined usually using pressure plate. If not available, then soil texture can be used to find the curve for similar soil from references.

Wish you the best

Burhan

Hello noha

To determine field capacity, permanent wilting point and hydraulic conductivity can use pedotransfer equations. These are functions that allow you to calculate these parameters using some soil characteristics (texture, BD, SOC). Some of these equations are those of Saxton, van Genutchen, Cambell, and Rawls.

Greetings.