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 19 95, 1996, and 1997 growing seasons. The lysimeters were constructed of 4.8- mm hot-rolled steel and were 0.91 x 1.02 x 0.61 m in size with an internal area of 0.929 m(2). The weight of a lysimeter containing only moist soil wa s 1,110.27 kg. At the beginning of each season of use, several tests were c onducted on the weighing system to determine if it was sensitive enough to give adequate results of crop water use. In 1995, rests were conducted on l inearity, repeatability, thermal shift, and creep errors. The values were /- 0.062 kg, +/-0.12 kg, -0.007 kg/degreesC, and -0.242 kg, respectively. T he terminal linearity was 0.082 kg (1996) and 0.043 kg (1997). The measurem ent uncertainty decreased as the number of lifts increased. The results sho wed that the system was capable of producing adequate results for determini ng crop water use.