Modeling the effect of biodegradable paper and plastic mulch on soil moisture dynamics

Abstract

Plastic mulch films are often used in agriculture to conserve soil moisture. Most of the plastic mulch currently used worldwide is made of non-biodegradable polyethylene, which has to be removed and disposed after harvest, incurring significant environmental costs. Biodegradable paper or plastic mulch could offer a valuable alternative to polyethylene. The objective of this study was to compare the effects of biodegradable mulches and standard polyethylene mulch on soil moisture dynamics during a growing season. A field experiment was carried out with pumpkin (Cucurbita pepo), which were irrigated and grown on raised beds covered with the following mulch treatments: no mulch, biodegradable paper, biodegradable plastic, and polyethylene. Soil moisture was measured at 10- and 20-cm depths. A numerical model (HYDRUS-2D) was used to simulate the moisture dynamics under the different mulch treatments, each represented by different boundary conditions at the soil surface. Polyethylene mulch, which created an impermeable surface layer, effectively reduced evaporation and maintained highest water content among the treatments. Biodegradable paper mulch, which was partially permeable to evaporation and rainfall throughout the growing season, resulted in soil moisture that was intermediate between that obtained for no mulch and polyethylene. Biodegradable plastic mulch, which was similar to that of polyethylene mulch initially in terms of effects on soil moisture, disintegrated during the growing season and allowed rainfall to penetrate and water to evaporate from the soil surface. Field data and model simulations both indicate that the biodegradable paper and plastic mulches provide comparable soil moisture dynamics as polyethylene mulch.