Biodegradable and non-biodegradable plastic mulches enhance chili production in Sri Lankan wet zone agriculture

Plastic film mulching (PFM) enhances plant growth and productivity by modifying soil properties. In Sri Lanka, the adoption of PFM is gradually rising, especially for high-value crops. However, its influence on soil remains a topic of significant scrutiny, especially in environmentally delicate locations such as the wet zone (WZ) of Sri Lanka. This research examines how different PFMs affect soil physicochemical properties and plant performance in chili production within the WZ. Chili (Capsicum annuum cv. MICH HY-1) was cultivated under a non-biodegradable low-density polyethylene (LDPE) mulch (PEUK), a reflective LDPE mulch, a PLA-PBAT biodegradable mulch (BD) and no mulch film application for one growing season. Soil physicochemical properties (pH, EC, moisture, nutrients and temperature), plant height and leaf chlorophyll content (SPAD) were measured monthly. The fresh biomass of roots, leaves, stems and remaining fruits was measured at the end of the season. This study demonstrated that mulching effectively conserved soil NO3– and available P while having no significant impact on NH4+ levels. Mulching increased gravimetric moisture content (GMC) and soil temperature compared to the control, with PEUK achieving the highest soil temperature (36.3 ± 0.71 °C). Mulching did not influence soil pH, but the control consistently had the lowest EC (17.6 ± 1.54 µS·cm−1). Mulching significantly improved plant height (PEUK of 70.2 ± 1.7 cm), SPAD (PEUK of 65.6 ± 1.4), yield (BD of 1230 ± 84 g) and fresh biomass relative to the control (height of 58.8 ± 2.3 cm, SPAD of 49.7 ± 1.5 and yield of 736 ± 59 g). Overall, the findings demonstrate that biodegradable mulch performed similarly to non-biodegradable plastic mulches in improving both soil properties and crop yield, indicating it could be a sustainable alternative for chili production in wet tropical regions.