Effects of Enhanced APG Surfactant on Leaching and Wettability of Six Bark Substrates

Abstract

Alkyl phenol ethoxylate (APE) surfactants are used in horticultural substrates but are considered nonbiodegradable, whereas others such as alkyl polyglucoside (APG) are derived from biodegradable sugar compounds. APE reduced total porosity (TP), container capacity (CC), and aeration porosity (AP) whereas APG with polyalkylene oxide block copolymer surfactant (APG/BLK) increased TP, CC, and AP for some substrates but other substrates remained unaffected by either surfactant. We determined substrate leaching fraction (LF) and wettability rating (WR) after drenches of 0.003 to 0.2 mL·L−1 APG/BLK for six bark substrates for three wetting cycles. After the third wetting cycle, five substrates had reduced LF and increased WR. Drenches of 0.2 mL·L−1 APE or APG/BLK for three wetting cycles indicated that APE was more efficacious than APG/BLK for reducing LF or increasing WR. APE was determined to be an effective surfactant for difficult-to-wet substrates, but drenching sometimes reduced TP. No reductions in TP were noted when using APG/BLK. Drenching rates of 0.003–0.2 mL·L−1 APG/BLK for three successive wetting cycles reduced LF and increased WR for most substrates, indicating potential usage for some horticultural applications.