Development and testing of a small weighable lysimeter system to assess water use by shallow-rooted crops

A mobile weighing system was designed in 1994 to weigh small lysimeters to measure water use by shallow-rooted crops. Using a reconditioned pesticide sprayer, a hoist, and a weighmeter, small lysimeters were weighed in the 1995, 1996, and 1997 growing seasons. The lysimeters were constructed of 4.8-mm hot-rolled steel and were 0.91×1.02×0.61 m in size with an internal area of 0.929 m². The weight of a lysimeter containing only moist soil was 1,110.27 kg. At the beginning of each season of use, several tests were conducted on the weighing system to determine if it was sensitive enough to give adequate results of crop water use. In 1995, tests were conducted on linearity, repeatability, thermal shift, and creep errors. The values were ±0.062 kg, ±0.12 kg, -0.007 kg/° C, and-0.242 kg, respectively. The terminal linearity was 0.082 kg (1996) and 0.043 kg (1997). The measurement uncertainty decreased as the number of lifts increased. The results showed that the system was capable of producing adequate results for determining crop water use.