Soil Surfactant Chemistries on Volumetric Water Content and Leachate of Greenhouse Substrates Under Two Irrigation Regimes.

Water retention is considered an important characteristic for selecting greenhouse substrates. Soil surfactants have the potential to improve water infiltration and water distribution uniformity throughout the substrates. To study how soil surfactants influence volumetric water content (VWC) and leachate volume in three horticulturally significant substrates, 96 leaching columns were filled with either Fafard 3B –surfactant, 80% sand: 20% peat, and washed sand. One of four surfactant treatments were applied to the substrate filled columns: (a) 10 % of an oleic acid modified block co-polymer, (b) 30 % of alkoxylated polyols and 21 % of glucoethers and (c) 50 % of nonionic polyols and 5 % 1,2-propanediol, or (d) water control. Columns were irrigated either once a week (ONCE) or as two applications a week (SPLIT). The experiment was conducted at the Clemson University Greenhouse Complex for ten weeks and then repeated. The VWC was measured at 5, 10, 15 and 25 cm column depths three times a week. Percolate volume were measured after soil surfactants and irrigation was applied.

Applying a surfactant alone did not reduce percolate, but when used in conjunction with SPLIT irrigation, there was a 42 -75% reduction in percolate compared to surfactant with ONCE irrigation. Regardless of the soil substrate, more water was retained when soil surfactants were applied. Incorporating SPLIT irrigation applications and surfactants provides a more optimal root zone environment for plant growth and reduces the potential of water loss (and water constituents) to the surrounding environment.