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United States Department of Agriculture

Agricultural Research Service

Title: Continuous columns for determining moisture characteristic curves of soilless substrates

Authors
item Altland, James
item Mielcarek, Marta - OREGON STATE UNIV.
item Owen, James - OREGON STATE UNIV.
item Zazirska, Maqdalena - OREGON STATE UNIV.

Submitted to: Southern Nursery Association Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 2007
Publication Date: November 1, 2007
Citation: Altland, J.E., Mielcarek, M., Owen, J., Zazirska, M. 2007. Continuous columns for determining moisture characteristic curves of soilless substrates. Southern Nursery Association Proceedings. 52:538-542.

Technical Abstract: Sound water management is essential for effectively producing nursery crops. Understanding substrate water availability is a critical component to managing irrigation properly. The objective of this paper is to report a method for generating moisture characteristic curves of soilless substrate that is quick, inexpensive, and offers greater precision at low tensions. Douglas fir (Pseudotsuga menziesii) bark (DFB) [screened to 0.9 cm (0.4 in)] was collected from stockpiles intended for nursery container production (Marr Bros. Monmouth, Ore.). Unscreened pumice (<0.95 cm (0.38 in), Pro-Gro, Sherwood, OR) and Canadian sphagnum peat (Sun Gro Horticulture Canada Ltd., LAVAL, Quebec) were used to make three substrates including: 1) 70:30-DFB:pumice (by vol.); 2) 70:30 DFB:peat (by vol.); and 3) DFB (not amended). Substrates were adjusted to 1.5 g·g-1 mass wetness. The DFB substrate was used to generate moisture characteristic curves over multiple dates to ensure the procedure was reliably repeatable. The 70:30-DFB:pumice and 70:30-DFB:peat substrates were used to determine if our method was able to differentiate between substrates of presumably different water holding capacities. Moisture characteristic curves for DFB (not amended) were estimated on three dates. The lack of fit test indicated that lines were similar, demonstrating this procedure provides consistent results over time when analyzing a similar substrate. The procedure took one week each time it was performed (including: saturating, draining, freezing, and drying). This is a much shorter period of time than is required for other procedures that use some sort of applied pressure apparatus (4 to 6 weeks). The addition of peat increased the amount of easily available water from just 2% up to 16% and decreased water buffering capacity from 6% to 2% when compared to DFB substrate. With pumice (70:30-DFB:pumice), easily available water increased from 2% to 5% while water buffering capacity dropped from 6% to 1% when compared to non-amended DFB substrate.

Last Modified: 10/31/2014
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