Dear Madam, you are not wrong. The result are okay.

First what is the rooting depth of your crop?

Second, what was the amount of rain or irrigation?

Answering this two questions can lead to you noting where you erred, if it is there.

I did work for cabbage with a rooting depth of 0.4 metres. So if I know the water at 0-0.4 will be available water. The water content at say 0.6 m for me would be water lost to deep percolation.

Can you include me in your research? If you need me kindly contact me through researchgate messaging.

It becomes more difficult in calculations due to the depths measured, and the for desired calculations do not mesh well. But if you assume each measured depth is consistent with the moisture content nearest it as opposed to any other measurement. So the 0-6.5 cm depth use the 5 cm measurement; 6.5 - 9 cm use the 8 cm; 9-14 cm depth use the 10 cm; 14- 30 cm use the 20 cm. This too might create some issues, depending on the depths and thickness of the soil horizons and the differences in their physical properties. If you use MS Excel, a programmed spreadsheet would quickly take your 15 minute or hourly entrees, and make the programmed calculations. Because the placement of the measurements are not equidistant across the 30 cm depth, that might bring about the issue In calculations. The 20 cm measurement is basically covering 1/2 of the 30 cm depth, so with simple summing of the 5 readings, the weight needed based on the depth differences is not being considered.

Hi William F. Hansen

Thank you for the information.

I calculated with equidistance taking 8cm and 18 cm data, still getting the same results. Data of soil moisture are showing wetting and drying patterns but the change in soil moisture storage is not. I was thinking that if my process is wrong somewhere. Can you suggest to me any journal article calculating the change in soil moisture storage using a soil moisture sensor?

In a lysimeter, no water losses can occur laterally or vertically outside of container or boundary set, just evapotranspiration. In unbounded soil, water movement includes lateral, vertical and evapotranspiration. Soil horizons can also complicate uniform water movement, and as well issues with compaction, layering of different soil materials such as heavier clay mix and coarser layer of sand mix. Also soils unless on bedrock are not immediately bounded, so losses might occur below the 30 cm depth, or at outside of the 20 cm measurement zone. There was no mention of rainfall measurements, or anything about presence of litter layer, degree of cultivation or mixing, boundaries, elevation of adjacent water table or lateral groundwater flow and it’s influence, etc. If the plant rooting depths are no more than 10 cm, then any likely losses that occur at 20 cm might actually be deep losses, not evapotranspiration. It all becomes very complex, and perhaps that maybe why lysimeters are often considered in ET studies. Wetting and drying trends depend on rainfall and to some extent the availability of water and plants ability to open and close stomata to utilize water. Soil moisture sensors are not always perfect, so one might also check their calibration. With frequent time measurements, absorbed water from a rainfall event might show up and seem to disappear as it has not reached the next lower sensor, so the data may seem to show fluctuations in total amount.

Firstly, you could have to determine the root depth of your crop, and the respective bulk density of the soil profiles. And then, you can determine the available water content as; AW=(F.C-PWP)*Depth*Bulk density.[for each layers ]. F