Effect of biodegradable mulching plastics on soil chemical properties, greenhouse gas emission, and plant growth under aerobic and flooding conditions

This study aims to examine the effect of biodegradable mulching plastics on soil chemical properties, greenhouse gas emission, and paddy rice growth under flooding conditions to compare with aerobic upland soil conditions. Four treatments were set-up with sandy paddy soil. Incubation experiment was conducted using three materials under aerobic pre-flooding condition for 0-3 months and then anaerobic flooding conditions for 3 months, measuring soil pH, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) productions; rice growth, and yield. Amendments were biodegradable mulching sheets made of polybutylene adipate terephthalate (PBAT), or polybutylene-succinate (PBS), to compare with non-biodegradable mulching sheet made of low-density polyethylene (LDPE), mixed with paddy soil or without amendment (soil only; as control). Pot experiment was also conducted with the same materials, amended to the same soils, and rice seedings were transplanted 1 month after amendment and pre-flooding period under aerobic condition. During aerobic incubation, soil pH and CO2 was higher with plastics. N2O was produced during pre-flooding period, but no significant difference among the treatments. During anaerobic period, both CO2 and CH4 production were larger with biodegradable plastics with aerobically preincubated for 1 month than control and aerobically preincubated for 2-3 months. Rice growth, grain yield, and yield components had no significant difference among treatment, except gain number reduction with PBS. More CH4 was emitted with LDPE per yield scale. Biodegradable mulching plastics increased soil pH, CO2, and CH4 production under anaerobic conditions, although paddy rice growth was not affected. We need further examination with different materials, soils, and crop rotation.