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Lysimeters are used in the study of soil moisture used for plant growth be cause they isolate the system under study and permit the specific measurement of evapotranspiration, rainfall, dew formation, and water uptake by soils (Jensena). Lysimetry methods were reviewed by Harrold (9). These included repeated soil sampling for gravimetric determinations (Bryan and Brownb) and the maintenance of a constant water table in a lysimeter (12, 18, 20, 23, 24). Another popular technique is to record lysimeter weight either periodically or continuously to determine changes so that evapotranspiration rates can be computed. A number of methods for weighing lysimeters have been reported. The simplest, suitable only for small lysimeters, is to move the unit from the soil to a scale and weigh it (21). Larger units are frequently supported directly on a scale (6, 7, 8). This introduces the problem of maintaining the scale in the hostile environment that prevails in underground installations. Another technique is to float the lysimeter in a fluid such as oil and measure the fluid level required to maintain floatation (4, 10, 13, 15). The weight of the lysimeter can then be determined using Archimedes principle. Bloemen (1) described a hydraulic system in which the lysimeter was supported by three pressure cells. The lysimeter weight was determined by measuring the pressure in the cells.
a weighing system for lysimeters
Voisey, Peter W. and E.H. Hobbs 1972. A WEIGHING SYSTEM FOR LYSIMETERS. Canadian Agricultural Engineering 14(2):82-84.
82 - 84