Using a Soil Surfactant to Improve Kenaf Establishment under Deficit Irrigation

Abstract

Kenaf (Hibiscus cannabinus) is a fiber crop that grows well in tropical climates and has numerous potential industrial and environmental benefits. However, like many crops, it may be limited by sensitivity to water stress, particularly at the seedling stage. Soil surfactants are frequently used as soil amendments to increase the volumetric water content (VWC), particularly under deficit irrigation. Two greenhouse experiments were conducted to determine the emergence and growth response of kenaf to three irrigation regimes and a one-time soil surfactant application. Kenaf seeds were planted in native Margate fine sand soil (siliceous, hyperthermic Mollic Psamnaquent) and sprayed with a nonionic surfactant at 3 quarts/acre (7.5 L/ha) (1×) and subjected to three irrigation regimes of 3.5 ounces (100 mL) of water applied every day (ED), every other day (EOD), or every 4 days (E4D). In Expt. 2, an additional surfactant treatment applied at 6 quarts/acre (15 L/ha) (2×) was included. The percent emergence, plant height, postexperiment biomass, and volumetric water content data were collected. During Expt. 1, kenaf emergence was significantly inhibited by ED irrigation with 1× when compared with E4D with 1×. In Expt. 2, seed treated with the 2× rate emerged faster and had better overall emergence under all irrigation regimes when compared with no soil surfactant. There was a trend for better kenaf emergence when less water was applied. The ED irrigation increased biomass in both experiments; however, in Expt. 2, the 2× rate doubled the biomass in the ED irrigation regime, and both 1× and 2× rates increased biomass in the EOD and E4D irrigation regimes. Soil surfactant treatment significantly increased the VWC in ED in Expt. 1 on four dates; however, in Expt. 2, both surfactant treatments increased the VWC in E4D irrigation until 35 days after planting. The results of this experiment suggest that a one-time soil surfactant treatment did not inhibit kenaf emergence under any irrigation regime. Kenaf emergence and biomass was greater and VWC was lower when a 2× rate of soil surfactant was applied to soil. In hydrophilic disturbed native sand soils, a one-time soil surfactant application increased kenaf emergence under deficit irrigation and the 2× rate of soil surfactant increased biomass under every irrigation regime. To maximize water savings, this study indicated that kenaf seed could withstand four-times less water to improve emergence. To maximize biomass, ED irrigation with a 2× soil surfactant treatment was significantly better.

Keywords

• hibiscus cannabinus
• seed emergence
• soil repellency
• volumetric water content