Rapid Test to Assess Plant-Available Water-Holding Capacity of Soil-Biochar
Mixtures
EMSL Project ID
50601
Abstract
One of the oft-cited specific benefits of the application of biochar to soil has been its ability to increase the plant-available water-holding capacity (PAWC) of the soil, and thereby, primary productivity. Measurement of PAWC by standard methods, however, is a fairly involved process that can take days, if not weeks, to complete. Moreover, the increase in PAWC involves both the internal porosity of the biochar as well as new porosity created by gaps between the biochar particles and pre-existing soil particles (inter-particle porosity) and is expected to change over time as the biochar and soil particles adjust to their new neighbors. Multiple measurements over several years are likely to be required, further increasing costs. Consequently, it is both difficult and expensive to estimate the changes in PAWC expected when soil is amended with biochar. We propose to refine and calibrate an inexpensive, rapid method for measuring plant-available water-holding capacity (PAWC) of soil-biochar mixtures. The method is based on applying different levels of water potential to a sample using a centrifuge. The sample is supported by a filter membrane fixed midway in a centrifuge tube, thus allowing drainage into the bottom of the tube to occur. By adjusting the rotational speed of the centrifuge, the water potential can be changed quickly and PAWC determined in a matter of an hour or two (after overnight equilibration to saturate the samples). The method has been used by the PI to obtain estimates of PAWC for pure biochar samples diluted in silt-sized glass beads, but has yet to be applied to soil/biochar mixtures, for which some changes in apparatus and length of centrifugation time may be needed. The method also needs calibration with standard methods for determining PAWC, which will be accomplished outside of EMSL. With respect to use of EMSL facilities, the goals of the project are to perform the centrifuge-based testing using EMSL equipment located in EMSL laboratory space.
Project Details
Start Date
2018-11-01
End Date
2019-09-30
Status
Closed
Released Data Link
Team
Principal Investigator