Evaluating soil salts dynamics under biodegradable film mulching with different disintegration rates in an arid region with shallow and saline groundwater: Experimental and modeling study

Soil salinization caused by shallow, saline groundwater represents a serious threat to field productivity, especially in arid regions with intense soil evaporation. Plastic film mulching (PM) has been increasingly applied to reduce soil evaporation and alleviate soil salinity stress. However, PM introduces into the soil a significant amount of plastic residues. Although biodegradable film mulching (BM) is an ideal alternative to PM due to the degradability of these films, unreasonably high disintegration rates may reduce the benefits of the proposed solution. Understanding the effects of these factors on soil salinity is essential for designing management options for improving water productivity. A two-year cornfield experiment was therefore carried out during 2019-2020 to evaluate differences in soil salt dynamics among treatments with BMs with low, medium, and high disintegration rates (BML, BMM, BMH), one polyethylene film mulching (PM), and no mulching (NM). Additionally, the HYDRUS-2D model was used to evaluate the electrical conductivity of the saturation paste extract (ECe), soil salt fluxes, salt distributions, and salt mass balances in two-dimensional soil profiles under BML, BMM, BMH, PM, and NM. The results showed that calibrated HYDRUS-2D could precisely simulate soil salinity under different mulching treatments. There were large differences between various treatments in the middle and late crop growth stages (Days After Sowing [DAS] 61-140). The highest ECe among different BM treatments occurred in BMH. Additionally, the two-dimensional distribution of soil salinity under BM was affected by irrigation events. The high soil salinity stress area (ECe > 3.80 dS m(-1)) occurred one day after irrigation (DAS 108) only under BMH among different BM treatments. Meanwhile, root water uptake (RWU) and crop yield (CY) under BMH were significantly reduced due to excessive accumulation of soil salinity in the root zone under intensive soil evaporation conditions. Compared with BMH and BMM, BML increased CY and the leaching ratio of soil salts from the root zone due to its good performance in water conservation. Thus, BM with a low disintegration rate is more efficient in controlling soil salinization in soils with a shallow groundwater table than BMs with higher disintegration rates due to lower soil evaporation. The findings of this study improve the understanding of the mechanisms of salt dynamics under biodegradable film mulching with different disintegration rates. The study also recommends to the farmers and government a suitable disintegration rate of the biodegradable film that can be adopted to promote field productivity.