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Gypsum Blocks With water in short supply, Gypsum Blocks are an old water management technique that's making a comeback and worth taking a look at. Gypsum blocks have been around since the 1940's, making them one of the oldest methods of soil moisture measurement. The grower, with a hand held meter, can manually read the gypsum blocks. It remains one of the cheapest methods of water monitoring in the industry. A buried gypsum block absorbs and releases moisture similarly to the surrounding soil. As moisture levels fall in the surrounding soil and block, electrical conductivity through the block decreases, and meter readings fall. The readings you take give you an idea of how much moisture is being absorbed by the plants, and how fast it is being absorbed. From this information you can judge how often you need to irrigate. Gypsum
Blocks need to be installed at 1-foot intervals, up to 4 feet deep. It
is important to replace the soil with the block in the same depth as it
was removed to achieve an accurate reading of the soils at that depth.
The blocks need to be saturated with water before they are installed and
will take 2 to 3 days to adjust to the same moisture intensity as the
soil moisture in the surrounding ground. The average cost for the measuring devices are $6 per gypsum block and $150 for the meter. The blocks need to be replaced every year on tilled ground but could last for 5 years on fields such as alfalfa that are not row crops. The meter requires a new battery occasionally. We do not sell the blocks or meter out of our office. For the information booklet, "A Marshmallow on a String!" about gypsum blocks, contact South Big Horn Conservation District at 307 765-2483. Photo: Laura Galloway shows how to measure the depth and install the gypsum block as local producers watch.
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