Rooting Strategies: Laboratory Tank Experiments

At the Ohio State University greenhouse facility our research group is currently in the process of designing and constructing a series of 2D tanks to examine the influence of water and nutrients on the water and energy balances as well as the allocation of carbon to root zone. (Image: Illinois  Native Plant Guide, Natural Resources Conservation Service).

Greenhouse Summary

This experiment is conducted with 2-Dimensional tanks. The tanks were constructed out of 0.9525 cm (3/8 in) thick acrylic. The inner dimensions of the tanks are 80 cm (31.5 in) by 80 cm (31.5 in) by 6 cm (2.36 in), as shown in the Figure 2. Due to the narrow thickness of 6 cm, we can assume homogeneity in that dimension, thus allowing the experimentation to be considered 2-Dimensional. The tanks are wired with 15 Decagon 5TE soil moisture sensors arranged in 5 rows at depths of 10, 20, 30, 45, and 60 cm (see Figure 2). Directly beneath each of the three columns on sensors is a drainage hole, which simulates tiled agriculture. The bottom 10 cm of the tanks are fitted with a diagonal piece of acrylic which has two functions. First, it forces any drainage of water to come out the front face, which provides easier access. Second, it decreases the capillary height allowing the tanks to dry faster. In addition, the front face of the tank is removable. This allows for sensors to be replaced if need be and for easier excavation of roots at the end of the experiment. The tanks are located inside a climate controlled greenhouse that has available lighting.

In addition to the tanks, a variable-intensity rainfall simulator was constructed above the tanks to allow for uniform watering across the tanks. The rainfall simulator uses Toro Matched Precipitation Rate sprinkler nozzles.  Each sprinkler was positioned so that it waters one tank on each side spaced 23 cm (9 inches) from the sprinkler.  Each sprinkler head gives approximately 0.5 mm per hour intensity.  Three sprinklers are wired adjacently so that each tank can receive 0.5, 1.0, or 1.5 mm per hour intensity.

This setup allows for many different experiments to be run, including but not limited to, behavior of varietals, effects of microtopography, causes of hydraulic redistribution, resilience to climate change, effects of competition, effects of water table heights, effects of soil types on root growth and infiltration patterns.  Currently, a drought resistant corn is being compared with non-drought resistant corn under two different climate scenarios, a dry season and a wet season.