Effect of Biodegradable Mulch Film Decomposition Rate on Root-Zone Microclimate and Yield Formation in Cucurbit Crops Under Arid Conditions

Plastic film residues accumulating in agricultural soils represent a significant environmental challenge worldwide, driving demand for biodegradable alternatives. This three-year field study evaluated five commercially available biodegradable mulch films (polylactic acid [PLA], polyhydroxyalkanoate [PHA], thermoplastic starch [TPS], starch-polybutylene adipate terephthalate blend [PBAT], and paper-based mulch) against a conventional low-density polyethylene (LDPE) control on watermelon (Citrullus lanatus cv. 'Crimson Sweet') and cantaloupe (Cucumis melo cv. 'Topmark') plantations in Uzbekistan (40°51′N, 68°43′E). Key microclimate variables root-zone temperature at 5, 15, and 25 cm depths, volumetric soil water content (SWC), and CO₂ flux from soil surface were monitored continuously. Tensile strength degradation kinetics were modelled using a modified Avrami equation. Results showed that PBAT blend films maintained structural integrity for 85–92 days post-installation, matching the critical crop establishment period (65–70 days), while TPS films degraded prematurely within 38–42 days under field UV exposure. Root-zone temperature in PBAT plots was 2.9°C higher than in LDPE plots at 5 cm depth due to increased CO₂ flux from microbial film decomposition. Watermelon marketable yield in PBAT plots reached 41.3 t ha⁻¹, surpassing LDPE (38.6 t ha⁻¹) by 7.0%, with no statistically significant residue detected at harvest (p = 0.08). These findings provide quantitative design criteria degradation half-life, thickness-to-tensile-strength ratio, and UV stabilizer concentration for biodegradable mulch films optimized for arid Central Asian growing conditions.