which are used to construct these soil-moisture blocks - Gypsum blocks are most useful at water potentials ranging from 100 KPa to 1.5 MPa, while in wetter soils these units tend to disintegrate too quickly. - Nylon units consist of stainless steel electrodes separated and wrapped with three pieces of nylon fabric and they are assembled in perforated stainless steel casings. They are sensitive at higher soil-water contents than the gypsum units (approx. 10 KPa ) but require special care when installing, in order to assure correct soil-probe contact. - In fiberglass blocks, the electrodes are separated by fiberglass cloth but otherwise they are similiar in design and characteristics to the nylon units. - To reduce the shortcomings of the above resistance blocks, (low sensitivity at high water contents, bad contact with
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