Evaluation of a Sprayable Biodegradable Polymer Membrane (SBPM) Technology for soil water conservation in tomato and watermelon production systems

Reducing soil evaporation, especially in temperate climate zones, increases crop production. Plastic mulch films (PMFs) are very efficient in conserving soil water conservation; however, plastic pollution is raising environmental and human health concerns. Therefore, a newly developed Sprayable Biodegradable Polymer Membrane (SBPM) Technology was tested for its ability to conserve soil water, suppress weeds, modify soil temperature, and improve crop yields. Two-year field experiments were performed in tomato and watermelon cropping systems, where SBPM was compared to no mulch and PMF controls. SBPM loadings were 3.0, 1.0, 0.5, and 0.25 kg m⁻², with fumigation (F) and without fumigation (NF) in tomato, and 1.5, 1.0, 0.5, and 0.25 kg m⁻² in watermelon. In tomato, the soil volumetric water content (VWC) in the topsoil was significantly higher for all treatments compared to the control, in the following order: 1 kg m⁻² F > 0.5 kg m⁻² NF > 1 kg m⁻² NF > 0.5 kg m⁻² F > Control in 2016/17; and 3 kg m⁻² NF > Control > 0.5 kg m⁻² F > 3 kg m⁻² F > 0.5 kg m⁻² NF in 2018. With watermelon in 2017, VWC was lower in the topsoil of the SBPM treatments than with PMF, but higher during the 2018 trial when no crop was grown. The amount of conserved soil water appeared to be determined by the physical integrity (unevenness/holes/tears) of the SBPM and PMFs. Soil salinity increase/decrease was associated with the volume of infiltrating water in the different treatments. Soil temperature increased significantly under the highest SBPM loading of 3 kg m⁻² NF, using a 55 cm width of polymer coverage. The yield responses across treatments were not significant. Field experiments proved the effectiveness of the SBPM technology, but also highlighted some limitations of it when compared with conventional PMFs. The SBPM technology needs ongoing refinement to improve its sprayability, durability, biodegradability, and cost-effectiveness.