Development of a Continuous Closed Pipe System for Controlling Soil Temperature at the Lower Boundary of Weighing Field Lysimeters

The thermal regime of a large field lysimeter should be the same as of the surrounding soil. It is assumed that lysimeters with a construction depth larger than the expected root zone meet this condition. However, the installation of such large lysimeters is costly and not always feasible. Thus, a new method for the control of soil temperature at the lower boundary of large field lysimeters was developed. Our method enables for easy and prompt control of the soil temperature at the bottom of lysimeters. Differences in soil temperature between the lysimeter and surrounding soil increased to 1.6°C when the temperature control was switched off. The significance of the automated soil temperature control is twofold. First, the reliability of lysimeter measurements can be improved. Second, shallower lysimeters can be constructed. This significantly reduces the installation costs of field lysimeters.