Effect of black polyethylene mulching on soil temperature and water dynamics during onion and garlic cultivation using a weighable lysimeter

Under winter cultivation, onion (Allium cepa L.) and garlic (Allium sativum L.) are exposed to low-temperature stress and soil water stress during transplant establishment, overwintering, and regrowth in early spring.These stresses are directly linked to temperature drops and water loss in the root zone, and can lead to delayed initial growth and reduced establishment rate.Mulching is a method that buffers nighttime cooling of the soil and suppresses surface evaporation, thereby extending the retention of moisture in the topsoil.In this study, we monitored onion and garlic using weighable lysimeters filled with a silty clay loam soil.For each season, two treatments were established: no mulching and black PE (polyethylene).Soil water content (%) and soil temperature (C) were continuously measured at 10 cm and 30 cm depths.In lysimeters, black PE mulching consistently increased soil water content and stabilized root-zone temperature.At 10 cm depth, mean volumetric water content was 20 -22% without mulching and 24 -29% with mulching.At 30 cm, it also increased slightly during the cropping season.Mulching tended to buffer nighttime cooling and reduced the daily soil temperature range at 10 cm (about 5.0 -5.5C no mulching, 4.2 -5.0C mulching), indicating lower thermal stress during winter onion and garlic cultivation.These results demonstrate that, in silty clay loam soil, black PE mulching increases the availability and retention of water in the root during winter cultivation of onion and garlic, while simultaneously buffering the root zone thermal regime by moderating nighttime cooling and reducing daily range of soil temperature variation.This suggests that plastic mulching in winter season should be considered not only as a weed-control material, but as an environmental stabilization method that provides both water retention and thermal buffering for overwintered crops.