A practical soil moisture meter as a scientific guide to irrigation practices
1950
Bouyoucos, G.J.
A simple, rapid, and practical method is presented to measure the available moisture content of soils, and to act as a scientific guide to irrigation practices. It indicates when and how much to irrigate the soil and how deep the applied water has penetrated the soil. The method consists of an alternating current impedance meter and a plaster of parts block with two electrodes imbedded inside. The method is intended for farmers, fruit growers, greenkeepers, florists and others to enable them to irrigate practically and economically. Although the moisture meter is intended for practical purposes, it is quite accurate. However, it is not mended to replace the soil moisture bridge for the more scientific work. The method is accurate and dependable in measuring the available moisture content of soils. On account of capacitance effects arising from long wire leads and leading to erroneous moisture readings, the wire leads of the plaster of paris blocks should not be any longer than 10 feet. The method can be used as a guide to irrigation practice, not only in soils with average salt content, but also in soils containing rather large amounts of salts. The latter soils are irrigated at a higher level of available moisture content on the meter scale. The moisture scale on the meter applies only to the plaster of paris blocks and not to the nylon units. The plaster of paris blocks as made at the present time will last a long time in the soil, especially in well drained soils. Freshly made or new plaster of paris blocks contain traces of soluble salts which affect slightly the readings at first. However, these salts readily disappear after the blocks are in the soil for 2 or 3 days.
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