Biodegradable composite hydromulches for sustainable organic horticulture.

Surface-applied mulches help retain soil moisture and optimize soil temperature while preventing weed growth and benefiting many horticultural crops. The most common mulch material is low-density polyethylene (LDPE), is typically landfilled, buried, or burned at the end of growing season causing negative environmental impacts. The goal of this research was to develop soil-biodegradable, liquid-applied (i.e., hydromulch) alternatives to LDPE mulch and optimize formulations that are acceptable for organic horticulture. Hydromulch (HM) treatments contained mixtures of paper pulp, wood fiber, or hemp hurds (Cannabis sativa L.) combined with various tackifiers and water. The tackifiers were guar gum (Cyamopsis tetragonoloba (L.) Taub.), psyllium husk (Plantago ovata L.) , and camelina meal (Camelina sativa (L.) Crantz), included at various proportions. Hydromulch samples were tested for physical properties (density, water holding capacity, C:N ratio, soil adhesion) and mechanical properties (tensile strength, puncture resistance). Hydromulches containing no tackifiers were included as controls to determine if the addition of tackifiers resulted in enhanced mechanical properties. The results showed addition of 6 % guar gum tackifier improved the tensile strength and puncture resistance by 182 % and 91 % respectively compared to control sample, and HM formulations containing paper were 200 % or more stronger than those containing wood or hemp hurds. Increased tackifier proportion was found to improve most mechanical properties, with guar gum performing best. Blending of tackifiers resulted in an interaction that decreased strength. Hydromulches containing wood fiber and hemp hurds did not show promising results. Paper in HM formulations helped to reduce mulch porosity and improved adhesion to soil. Results from the study provide a foundation on optimal formulations for expanded trials at field-scale. • Hydromulch (HM) manufactured using paper, wood fibers, hemp hurds and organic tackifiers. • Paper based HM demonstrated high mechanical properties compared to wood fiber and hemp hurds. • Guar gum and psyllium husk are most promising tackifiers. • The amount of tackifier has direct influence on the puncture resistance and tensile strength of HM. [ABSTRACT FROM AUTHOR]