Evaluating the effects of biodegradable and plastic film mulching on soil temperature in a drip-irrigated field

The use of plastic film mulching (PM) has steadily increased in the past few decades due to many advantages compared to no film mulching (NM). However, PM also has many drawbacks, such as producing plastic film residues and causing high temperatures at later crop growth stages. Thus, biodegradable film mulching (BM) has recently been used as an excellent alternative solution. In this study, the effects of three mulching types, including PM, BM, and NM, on soil temperatures (Ts) are evaluated using field experiments. Three mulching types with an irrigation depth of 22.5 mm (i.e., PM22.5, BM22.5, and NM22.5) and three irrigation depths of 15, 22.5, and 30 mm with BM (i.e., BM15, BM22.5, and BM30, respectively) were compared. Additionally, the Ts fluctuations and distributions during different crop growth stages were simulated using HYDRUS (2D/3D). The results showed that HYDRUS (2D/3D) successfully simulated Ts with RMSE of 2.11–4.00 °C, EF of 0.63−0.85, and MRE of 8.1 %–11.6 % during the validation period. There were large differences in Ts among PM22.5, BM22.5, and NM22.5 in different crop growth stages. In the elongation and tasseling stages, Ts under PM22.5 and BM22.5 was not significantly different but markedly improved compared with NM22.5. In the filling and maturation stages, higher variability of Ts was observed under BM22.5 compared with PM22.5. The standard deviation (SD), the deviation variance (DV), and the kurtosis coefficient (K) under BM22.5 were by 6.7 %, 32.6 %, and 19.3 % higher than under PM22.5, while accumulated soil temperature (AT) and the ratio of effective accumulated soil temperature (AET, ≥10 °C) to AT (RT) decreased by 3.8 % and 4.0 %, respectively. Additionally, apparent differences in Ts between BM22.5 and PM22.5 appeared mainly in the soil surface layer (0−10 cm). The area with “optimal Ts” (i.e., corn growth is optimal in the Ts range of 20−24 °C) in the 0−30 cm soil layer increased by 33.5 % under BM22.5 compared with PM22.5. Moreover, Ts decreased with an increase in the irrigation depth from BM15 to BM22.5, and BM30, with the maximum size of the “optimal Ts” area under BM22.5. Generally, BM has more advantages in terms of heat preservation and preventing high temperatures compared with NM and PM, respectively. Therefore, the biodegradable film can be recommended as an alternative material to replace the traditional polyethylene film.