Soil-biodegradable plastic mulch films are a promising alternative to polyethylene mulches, but adoption has been slow, in part because of uncertainties about in-field degradation. The international biodegradability standard EN-17033 requires 90% degradation within 2 years in an aerobic incubation at constant temperature (20–28 °C). However, in-laboratory biodegradability does not guarantee in-field degradation will follow the same timeframe. Field test protocols are needed to assess biodegradable mulches under a range of environmental conditions and collate site-specific information to predict degradation. Our objectives were to (1) monitor in-field degradation of soil-biodegradable plastic mulches following successive applications and incorporations, (2) quantify mulch recovery 2 years after the final incorporation, and (3) compare in-field degradation with the laboratory standard in terms of calendar and thermal times based on a zeroth-order kinetics model. A field experiment was established in spring 2015 in Mount Vernon, WA testing five biodegradable mulches laid each spring and incorporated each fall until 2018. Mulch recovery was quantified every 6 months until fall 2020, 2 years after the final incorporation. While mulches were incorporated annually, recovery of visible fragments (>2.36 mm) was constant or decreasing over time, indicating mulch deterioration kept pace with new additions. In fall 2020, mulch recovery was 4–16% of total mulch mass incorporated. A zeroth-order kinetics model was used to analyze mulch degradation after the final application. Model extrapolations indicate it would take 21 to 58 months to reach 10% recovery (90% degradation), exceeding the laboratory standard's 24-month benchmark by up to a factor of 2.4. However, when the analysis is done with thermal time, better agreement between in-field and laboratory degradation rates is observed. While other factors, including soil type, soil moisture, and mulch fragment size are also at play, thermal time, rather than calendar time, will be more applicable for assessing site-specific, in-field mulch degradation.

土壤可生物降解塑料地膜是聚乙烯地膜的一种很有前途的替代品，但采用速度缓慢，部分原因是田间降解的不确定性。国际生物降解性标准 EN-17033 要求在恒温 (20–28 °C) 有氧培养中 2 年内降解 90%。然而，实验室内的生物降解性并不能保证现场降解将遵循相同的时间框架。需要现场测试协议来评估一系列环境条件下的可生物降解覆盖物，并整理特定地点的信息以预测降解。我们的目标是 (1) 在连续施用和掺入后监测土壤可生物降解塑料覆盖物的田间降解，(2) 量化最终掺入后 2 年的覆盖物恢复情况，(3) 基于零级动力学模型，在日历和热时间方面将现场降解与实验室标准进行比较。2015 年春季，在华盛顿州弗农山 (Mount Vernon) 开展了一项田间试验，测试了每年春季铺设并在 2018 年之前合并的五个可生物降解覆盖物。每 6 个月对覆盖物恢复进行一次量化，直到 2020 年秋季，即最终合并后 2 年。虽然每年都会加入覆盖物，但可见碎片（> 2.36 毫米）的回收率是恒定的或随着时间的推移而减少，这表明覆盖物的恶化与新添加物保持同步。2020 年秋季，覆盖物回收率为所包含的覆盖物总质量的 4-16%。使用零级动力学模型来分析最终应用后的地膜降解情况。模型推断表明，达到 10% 的回收率（90% 的降解）需要 21 到 58 个月，比实验室标准的 24 个月基准高出 2.4 倍。然而，当用热时间进行分析时，可以观察到现场和实验室降解率之间更好的一致性。虽然其他因素，包括土壤类型、土壤湿度和覆盖物碎片大小也在起作用，但热时间而不是日历时间将更适用于评估特定地点的田间覆盖物降解。