Soil Salt Accumulation Characteristics of Long-term Drip Irrigation in Cotton Fields During Non-irrigation Seasons

TAN Mingdong¹², WANG Zhenhua¹², WANG Yue¹², LI Wenhao¹², ZONG Rui¹², ZOU Jie¹²

¹College of Water Conservancy and Architectural Engineering, Shihezi University, Shihezi, Xinjiang 832000, China
²Key Laboratory of Modern Water-saving Irrigation of Xinjiang Production and Construction Corps, Shihezi, Xinjiang 832000, China

Abstract

The movement and transformation characteristics of soil water and salt during the freezing-thawing process in non-irrigation seasons directly affect spring crop irrigation decisions. This study conducted field sampling and monitoring on cotton fields with different drip irrigation years in the Xinjiang oasis irrigation area to explore the laws of soil water-salt transport during freezing-thawing and the salt accumulation characteristics in cotton fields under different drip irrigation durations. The results showed that: (1) During the freezing-thawing process, significant plot differences existed in soil salt movement characteristics in cotton fields. The wasteland (CK) plot exhibited a salt return trend, with an average salt flux of 172.57 g·m⁻²·d⁻¹. (2) With increasing drip irrigation years, the salt distribution pattern in cotton fields shifted from surface accumulation to deep-layer accumulation. (3) The ablation period was the most active period for water and salt transport in both wasteland and cotton field plots. After freezing-thawing, the sensitive zone (0–60 cm) of all plots showed increased soil water storage, with increments of 23.43 mm, 81.26 mm, 31.68 mm, 62.39 mm, 96.98 mm, and 69.64 mm for the wasteland and cotton fields with 13, 15, 17, 19, and 23 drip irrigation years, respectively. This study reveals the laws of soil water-salt transport during the freezing-thawing process and the salt accumulation characteristics in cotton fields under long-term drip irrigation, providing scientific guidance for soil management in Xinjiang under non-irrigation season freeze-thaw conditions and long-term drip irrigation.

Keywords: drip irrigation cotton field; freeze-thaw; salt flux; salt accumulation; water loss

Introduction

Compared with traditional irrigation methods, mulched drip irrigation technology has been widely adopted in arid and semi-arid regions due to its excellent water-saving and moisture-preserving performance. As the most typical demonstration area for mulched drip irrigation technology in China, Xinjiang's mulched drip irrigation area has exceeded 1.28×10⁶ hm². However, during the large-scale promotion and application of mulched drip irrigation technology in Xinjiang, most drainage ditches have been filled, causing soil salts to lose their pathway for removal and merely redistribute within the soil profile, with salts continuing to accumulate in the soil body. A salt淡化层 (desalination layer) forms in the tillage layer, creating a "desalination illusion" that ensures normal crop growth and development in the short term, but soil surface salt content remains high after spring. The contradiction between desalination and salt accumulation in long-term mulched drip irrigation cotton fields persists.

Soil salt content directly affects cotton growth, but the application of mulched drip irrigation technology significantly reduces shallow soil salt content, thereby potentially improving cotton emergence rate and yield. Therefore, investigating the impact of seasonal freezing-thawing on soil salt spatiotemporal changes in cotton fields with different drip irrigation years is crucial for scientifically guiding spring irrigation decisions and ensuring the sustainable development of mulched drip irrigation technology.

In countries and regions with extensive seasonal frozen soils, the movement and distribution patterns of soil water-salt during freezing-thawing have long been research hotspots. Understanding water and salt movement during freezing-thawing is essential for rational land resource development, crop yield improvement, and saline-alkali disaster prevention. Non-irrigation season soil salt movement occurs throughout the entire freezing-thawing process. Due to temporal and spatial variations in ground temperature during freezing, soil undergoes periodic freezing and thawing. During top-down freezing, soil water phase-changes into ice, creating significant soil-water potential gradients above and below the frozen layer that drive salt transport from bottom to top, making surface salt accumulation possible during freezing. However, some scholars argue that during the ablation period, large amounts of snowfall and melting of "frozen layer detained water" can effectively leach surface soil salts, resulting in surface desalination. Conversely, other studies suggest that strong evaporation and snowmelt during spring ablation can raise the groundwater level, intensifying surface salt accumulation, and that freeze-thaw action is a primary driver of soil salinization. Therefore, the spatiotemporal distribution changes of soil water-salt in cotton fields during non-irrigation seasons have non-negligible effects on cotton growth.

This study conducted natural soil sampling observations on five cotton fields with different drip irrigation years to reveal salt migration laws during freezing-thawing and salt accumulation characteristics under different drip irrigation durations, providing a scientific basis for the sustainable application of mulched drip irrigation technology in oasis cotton fields.

1. Materials and Methods

1.1 Study Area Overview

The experimental site is located at the 121st Regiment of the 8th Division, Xinjiang Production and Construction Corps (85°32′47″–85°34′15″E, 44°45′85″–44°48′48″N). The region has a typical temperate continental climate and is a typical seasonal frozen soil area. In 2020, the total annual rainfall was 84.3 mm, with a daily average temperature of 8.37°C, maximum temperature of 38.7°C, and minimum temperature of -27.1°C. During the experimental period (December 2019 to March 2020), total precipitation was 38.5 mm and average temperature was -8.56°C.

This study selected five cotton fields that began using mulched drip irrigation technology in 1997, 1999, 2003, 2005, and 2007 (with 23, 19, 17, 15, and 13 drip irrigation years, respectively), plus a wasteland plot as control (CK). The cotton fields had uniform field management and consistent irrigation systems. Before freezing, all cotton fields received the same winter irrigation quota of 2250 m³·hm⁻².

1.2 Sample Collection and Measurements

1.2.1 Soil Moisture and Salt Content

Soil samples were collected during three freezing-thawing stages: pre-freezing (December 15, 2019), freezing period (January 23, 2020), and ablation period (March 5, 2020). Soil samples were obtained using an auger. To eliminate horizontal salt differences caused by drip irrigation, three sampling zones were established in each cotton field, with three sampling points at 50 cm horizontal spacing in each zone. Sampling depths were 0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm, 40–50 cm, 50–60 cm, 60–70 cm, 70–80 cm, 80–90 cm, 90–100 cm, 100–120 cm, 120–140 cm, 140–160 cm, 160–180 cm, and 180–200 cm. Soil samples from the same depth in each plot were mixed, and the average of the three sampling zones was used as the representative data for each plot.

Soil mass water content was determined using the oven-drying method. After drying, soil samples were ground and passed through a 1 mm sieve. A 1:5 soil-water ratio extract was prepared, shaken for 5 minutes, settled, filtered, and the supernatant was used to measure electrical conductivity (EC) with a DDS-11A conductivity meter. Soil total salt content was calibrated using the residue method, with calibration results shown in Figure 2.

1.2.2 Soil Salt Storage and Salt Flux

The salt storage (referred to as salt storage) per unit area (1 m²) in the h-depth soil layer was calculated using Equation (1):

$$
S = \gamma \times C \times h \times \frac{1}{10}
$$

where:
- $S$ is the salt storage in the h-depth soil layer (g·m⁻²)
- $\gamma$ is the dry bulk density of the soil layer (g·cm⁻³)
- $C$ is the soil salt content (g·kg⁻¹)
- $h$ is the soil layer depth (cm)

Assuming one-dimensional vertical salt movement in soil, salt flux was calculated using Equation (2):

$$
Q_i = \frac{\Delta S_i}{t}
$$

where:
- $Q_i$ is the salt flux at the upper and lower interfaces of the target soil layer (g·m⁻²·d⁻¹)
- $\Delta S_i$ is the change in salt storage in the i-th soil layer (g·m⁻²)
- $t$ is the duration of the period (d)

By definition, if $Q > 0$, the soil layer accumulated salt during the calculation period; if $Q < 0$, salt content decreased.

1.2.3 Soil Water Storage and Water Loss

The water storage in the h-depth soil layer was calculated using Equation (3):

$$
W = \gamma \times \theta \times h \times \frac{1}{10}
$$

where:
- $W$ is the water storage in the h-depth soil layer (mm)
- $\theta$ is the soil mass water content (%)

Water loss was calculated using Equation (4):

$$
\Delta W = W_i - W_j
$$

where:
- $\Delta W$ is the soil water storage loss (mm)
- $W_i$ is the water storage in the previous stage (mm)
- $W_j$ is the current water storage (mm)

When $\Delta W > 0$, it indicates water loss; when $\Delta W < 0$, it indicates water gain.

1.3 Data Analysis

Data were organized and preprocessed using Excel 2010. One-way ANOVA was performed using SPSS 20.0 software, and figures were created using Origin 2020 software.

2. Results

2.1 Soil Salt Distribution Characteristics

2.1.1 Spatiotemporal Distribution of Soil Salt in Cotton Fields with Different Drip Irrigation Years

The vertical salt distribution in the wasteland plot during the pre-freezing period showed that wasteland salt storage decreased layer by layer down the profile, with maximum surface soil salt storage (1809.84 g·m⁻²), representing a typical surface-accumulation profile (Figure 3). In drip irrigation cotton fields, salt storage showed an increasing trend with depth, representing a bottom-accumulation profile (Figure 3).

Analysis of total salt storage in each soil layer of cotton fields with different drip irrigation years during the pre-freezing period revealed that total salt storage in the 0–60 cm and 60–120 cm layers decreased significantly with drip irrigation years (P < 0.05), with determination coefficients (R²) of 0.83 and 0.89, respectively. Although total salt storage in the 120–200 cm layer and the entire profile also showed decreasing trends (R² = 0.43 and 0.44, respectively), the changes were not significant with drip irrigation years (Figure 4).

2.1.2 Evolution Characteristics of Soil Salt in Cotton Fields with Different Drip Irrigation Years

With increasing drip irrigation years, the salt distribution pattern in cotton fields shifted from surface-accumulation to uniform distribution. The cotton field with 23 drip irrigation years showed minimal overall fluctuation in soil salt distribution, with significantly lower deep soil salt storage than other plots, indicating that salt distribution had become uniform in the vertical direction (Figure 3). This finding is consistent with Li et al.'s research results on soil salt dynamics under different cultivation periods. However, the leaching effect on soil salt in the 0–120 cm layer was not significant, demonstrating the limitations of drip irrigation in salt leaching. Salts persist in the soil profile, and combined with strong surface evaporation and groundwater dynamics, the probability of soil salinization increases.

2.2 Water-Salt Transport During Freezing-Thawing

2.2.1 Salt Accumulation Characteristics During Freezing-Thawing

During the pre-freezing period, salt in all plots moved downward, with the wasteland showing significantly greater movement than drip irrigation plots. The average salt flux was -155.59 g·m⁻²·d⁻¹, decreasing with depth, indicating overall salt leaching and reduced soil salt content during this period. Drip irrigation plots showed less intense salt movement than the wasteland. During this period, except for salt accumulation in the 30–70 cm layer of the 13-year plot and the 120–140 cm layer of the 15-year plot, all other layers in drip irrigation plots showed decreased salt content. Notably, the wasteland 0–20 cm layer had an average salt flux of -59.20 g·m⁻²·d⁻¹, while the 13-year, 15-year, 17-year, and 19-year plots had fluxes of -5.83, -5.08, -0.88, and -0.55 g·m⁻²·d⁻¹, respectively.

During the freezing period, soil salt changes were smaller, with salt flux amplitudes significantly lower than in the pre-freezing period. The wasteland 0–120 cm layer, the 13-year plot 40–180 cm layer, and the 15-year plot 20–200 cm layer continued to show decreased salt content, with average salt fluxes of -53.87 g·m⁻²·d⁻¹. Another pattern showed overall salt increase, with flux amplitude increasing with depth. For example, the wasteland and 23-year plot had average salt fluxes of 43.61 and 172.57 g·m⁻²·d⁻¹, respectively. The remaining layers showed salt accumulation, with the 23-year plot showing overall salt increase and flux increasing with depth, averaging 5.67 g·m⁻²·d⁻¹.

The ablation period was the most active period for soil salt movement in all plots. During this period, salt changes could be divided into two patterns. One pattern showed overall decrease, with flux decreasing with depth, as seen in the 13-year, 15-year, and 17-year plots, with average salt fluxes of -61.46, -53.87, and -2.08 g·m⁻²·d⁻¹, respectively. The other pattern showed overall increase, with flux increasing with depth, as seen in the wasteland, 19-year, and 23-year plots, with average salt fluxes of 38.18, 10.53, and 172.57 g·m⁻²·d⁻¹, respectively, indicating salt return trends.

2.2.2 Water Loss Characteristics During Freezing-Thawing

Based on water storage distribution in each plot during the freezing-thawing period, the soil profile could be divided into three zones: the 0–60 cm sensitive zone, the 60–120 cm stable zone, and the 120–200 cm deep active zone. The sensitive zone was most affected by solar radiation, sunshine intensity, temperature, and other environmental factors, where water was easily lost and recovered. This zone was also the main root growth area for cotton, and its dynamic water storage changes directly affected root growth, making it the focus of this analysis. The stable zone showed minimal water storage fluctuations and relatively stable distribution characteristics, being less affected by external factors. The deep active zone's water storage fluctuations were mainly influenced by groundwater dynamics, showing strong variability.

Analysis of water loss in the sensitive zone of each plot revealed that during the pre-freezing period, the wasteland sensitive zone water storage decreased by 3.89 mm, while other drip irrigation plots increased by an average of 14.82 mm. During the freezing period, the 13-year plot water storage decreased by 45.89 mm, while other plots increased. During the ablation period, all plots showed increased water storage, with an average increase of 20.98 mm. After the complete freeze-thaw cycle, the wasteland and drip irrigation cotton field sensitive zone water storage increased by 23.43 mm and 81.26 mm, 31.68 mm, 62.39 mm, 96.98 mm, and 69.64 mm, respectively, with the ablation period being the main contributor to soil water storage increase.

3. Discussion

This study found that salt distribution patterns shifted from surface-accumulation to uniform distribution with increasing drip irrigation years. The 23-year plot showed minimal vertical fluctuation in soil salt distribution, with significantly lower deep soil salt storage, indicating uniform vertical salt distribution. This aligns with Li et al.'s research on soil salt dynamics under different cultivation periods. However, the leaching effect on 0–120 cm soil salt was not significant, demonstrating the limitations of drip irrigation in salt leaching. Salts persist in the soil profile, and combined with strong surface evaporation and groundwater dynamics, the risk of soil salinization increases.

Zhang et al. found that 0–60 cm soil salt accumulated with drip irrigation years, which differs from our conclusions. This discrepancy is due to their use of brackish water irrigation (average salt content 2.52 g·L⁻¹), where external salt input was the main cause of soil accumulation. Notably, this study collected salt data after cotton harvest, representing a relatively stable salt state after irrigation cessation, allowing more objective comparison of salt changes among plots with different drip irrigation years. Previous studies often collected data during the growing season when salt dynamics were more affected by current irrigation regimes.

Salt flux is a powerful parameter for characterizing salt movement between soil layers and depicting salt accumulation features. Li et al. found that 0–140 cm soil salt storage decreased before and after freezing-thawing, suggesting natural freeze-thaw cycles could leach cotton field salts, but their study lacked analysis of salt movement during the freeze-thaw process. In this study, during the pre-freezing period, 0–120 cm salt moved downward in all plots, with flux decreasing as drip irrigation years increased. This was mainly due to significantly reduced salt content in this layer with drip irrigation years, weakening salt movement intensity. During the freezing period, plot differences emerged: the 13-year plot showed upward salt movement in all layers, while other plots showed alternating positive and negative fluxes in different layers, similar to Peng et al.'s findings. During the ablation period, except for the 13-year plot, all other plots showed overall upward salt movement, indicating salt return trends, consistent with Kang et al. and Zhang et al. The 13-year plot continued to show downward salt movement,呼应ing Li et al.'s conclusion about frozen layer detained water leaching salts. This study found that wasteland salt changes were more dramatic than cotton fields during the pre-freezing period, possibly due to long-term mulched drip irrigation altering soil structure, particle arrangement, and pore distribution, changing salt movement pathways and reducing salt movement amplitude during freeze-thaw.

Xinjiang's arid oasis cotton fields are crucial for economic crops. To inhibit post-thaw salt return affecting cotton growth after spring sowing, this study suggests that under current irrigation regimes, cotton straw mulching could be implemented during non-irrigation seasons to reduce soil water evaporation while suppressing salt return. Additional leaching quotas could be applied, but water resource conservation must be considered.

The ablation period contributed most to water increase in the sensitive zone (Table 1). Although there remains a time interval between monitoring and cotton sowing, during which temperatures will continue rising and precipitation is scarce, soil water will likely be in a state of loss. Since cotton in this region follows a "dry sowing and wet emergence" pattern, water loss during this period will determine the emergence irrigation quota. Previous studies indicate that surface mulching during the annual or freeze-thaw period effectively preserves soil water. Shan et al. noted that mulching during the freeze-thaw period is more practical for water conservation. Therefore, to maintain soil water and conserve water resources, straw mulching of cotton fields during the freeze-thaw period is recommended, which also positively prevents soil frost damage and conserves water.

4. Conclusions

Based on analysis of soil water and salt changes during freezing-thawing in five cotton fields with different drip irrigation years, the following conclusions were drawn:

1) With increasing drip irrigation years, soil salt storage in the 0–120 cm layer of cotton fields decreased significantly (P < 0.05), and salt distribution patterns shifted from surface-accumulation to bottom-accumulation types.

2) During the pre-freezing period, 0–20 cm soil salt in the wasteland moved downward with an average salt flux of -59.20 g·m⁻²·d⁻¹, while the 13-year, 15-year, 17-year, and 19-year plots had average fluxes of -5.83, -5.08, -0.46, and -0.55 g·m⁻²·d⁻¹, respectively. During the freezing and ablation periods, plot differences in salt movement emerged. During freezing, the 13-year plot showed overall salt increase with an average flux of 5.67 g·m⁻²·d⁻¹, while other plots showed alternating positive and negative fluxes in different layers. During ablation, the wasteland and 19-year and 23-year plots showed overall salt increase, indicating salt return trends.

3) The 0–60 cm layer was the sensitive zone for soil water storage in drip irrigation cotton fields. After freezing-thawing, water storage in this zone of the wasteland and the 13, 15, 17, 19, and 23-year plots increased by 23.43 mm, 81.26 mm, 31.68 mm, 62.39 mm, 96.98 mm, and 69.64 mm, respectively, with the ablation period being the main contributor to soil water storage increase.

References

[1] Westarp S V, Chieng S, Schreier H. A comparison between low cost drip irrigation, conventional drip irrigation, and hand watering in Nepal[J]. Agricultural Water Management, 2004, 64(2): 143-160.

[2] Ning Songrui, Zuo Qiang, Shi Jianchu, et al. Water use efficiency and benefit for typical planting modes of drip irrigated cotton under film in Xinjiang[J]. Transactions of the Chinese Society of Agricultural Engineering, 2013, 29(22): 90-99.

[3] Statistics Bureau of Xinjiang Production and Construction Crops. Xinjiang Production & Construction Corps Statistical Yearbook[M]. Beijing: China Statistics Press, 2020.

[4] Li Yi, Wang Wenyan, Wang Quanjiu. A breakthrough thought for water saving and salinity control in arid and semi arid area under trickle irrigation[J]. Irrigation and Drainage, 2001, 20(2): 42-46.

[5] Wang Zhenhua, Yang Peiling, Zheng Xurong, et al. Soil salinity changes of root zone and arable in cotton field with drip irrigation under mulch for different years[J]. Transactions of the Chinese Society of Agricultural Engineering, 2014, 30(4): 90-99.

[6] Zhang Dianfa, Zheng Qihong, Dong Zhiying. Mechanism of soil salt moisture transfer under freeze thawing condition[J]. Bulletin of Soil and Water Conservation, 2005, 25(6): 14-18.

[7] Li Weiqing, Lei Yuping, Zhang Xiumei, et al. Study of water and salt migration in soil under concrete mulch during freezing/thawing period[J]. Journal of Glaciology and Geocryology, 2001, 23(3): 251-257.

[8] Fang Rulin. Preliminary study on the dynamical regime of water and salt during the freezing and thawing period of soil[J]. Acta Pedologica Sinica, 1982, 19(2): 164-172.

[9] Wang Weizhen, Wu Yueru, Jin Rui, et al. Analysis of the variation characteristics of soil moisture and soil salinity: Take Arou Pasture in the upper reaches of Heihe River for an example[J]. Journal of Glaciology and Geocryology, 2009, 31(2): 268-274.

[10] Li Ruiping, Shi Haibin, Takeo Akae, et al. Characteristics of air temperature and water salt transfer during freezing and thawing period[J]. Transactions of the Chinese Society of Agricultural Engineering, 2007, 23(4): 70-74.

[11] Zhou Youwu. Frozen Soil in China[M]. Beijing: Science Press, 2000.

[12] Brouchkov A. Salt and water transfer in frozen soils induced by gradients of temperature and salt content[J]. Permafrost & Periglacial Processes, 2015, 11(2): 153-160.

[13] Cary J W, Mayland H F. Salt and water movement in unsaturated frozen soil[J]. Soil Science Society of America Journal, 1972, 36(4): 549-555.

[14] Gray D M, Granger R J. In situ measurements of moisture and salt movement in freezing soils[J]. Canadian Journal of Earth Sciences, 1986, 23(5): 696-704.

[15] Liu J, Yang P, Yang Z J. Water and salt migration mechanisms of saturated chloride clay during freeze thaw in an open system[J]. Cold Regions Science and Technology, 2021, 186(8): 103277.

[16] Shafique U, Anwar J, Munawar M A, et al. Chemistry of ice: Migration of ions and gases by directional freezing of water[J]. Arabian Journal of Chemistry, 2016, 9(1): 47-53.

[17] Ye X, Huang Z G, Fan Y, et al. Dynamics of soil moisture and salt content after infiltration of saline ice meltwater in saline sodic soil columns[J]. Pedosphere, 2017, 27(6): 1116-1124.

[18] Li Wenhao, Wang Zhenhua, Zheng Xurong, et al. Effects of freezing and thawing on soil salinity in cotton fields by long term drip irrigation of saline alkaline soil in North Xinjiang[J]. Agricultural Research in the Arid Areas, 2015, 33(3): 40-46.

[19] Peng Zhenyang, Huang Jiesheng, Wu Jingwei, et al. Salt movement of seasonal freezing thawing soil under autumn irrigation condition[J]. Transactions of the Chinese Society of Agricultural Engineering, 2012, 28(6): 77-81.

[20] Kang Shuangyang, Gao Weiyue, Wang Fenge. Regularity of water and salt movement in soil in Hetao Irrigated Region, Inner Mongolia, during freezing melting period[J]. Yellow River, 1987, 39(5): 45-49.

[21] Zhan Dianfa, Wang Shijie. Mechanism of freeze thaw action in land salinization process: As an sample in west Jilin Province[J]. Bulletin of Soil and Water Conservation, 2000, 20(6): 14-17.

[22] Jin Shanshan, Wang Xing, Wang Youke, et al. Effects of typical mulching patterns on soil water loss in jujube land during dormancy period[J]. Transactions of the Chinese Society of Agricultural Engineering, 2016, 32(14): 153-160.

[23] Li Baofu, Xiong Heigang, Zhang Jianbing, et al. Dynamic of soil salt in soil profiles different in cultivation age and its affecting factors[J]. Acta Pedologica Sinica, 2010, 47(3): 429-438.

[24] Liu Xinyong, Tian Changyan. Study on dynamic and balance of salt for cotton under plastic mulch in south Xinjiang[J]. Journal of Soil and Water Conservation, 2005, 19(6): 84-87.

[25] Tan Junli, Kang Yuehu, Jiao Yanping, et al. Effects of cropping years on soil salinity and pH value in fields under drip irrigation condition[J]. Transactions of the Chinese Society of Agricultural Engineering, 2009, 25(9): 43-50.

[26] Zhang Wei, Lyu Xin, Li Luhua, et al. Salt transfer law for cotton field with drip irrigation under the plastic mulch in Xinjiang Region[J]. Transactions of the Chinese Society of Agricultural Engineering, 2008, 24(8): 15-19.

[27] Yao Baolin, Li Guangyong, Wang Feng. Effects of winter irrigation and soil surface mulching during freezing thawing period on soil water, heat, and salt for cotton fields in south Xinjiang[J]. Transactions of the Chinese Society of Agricultural Engineering, 2016, 32(7): 114-120.

[28] Shan Xiaoqin, Zheng Xiuqing. Impacts of surface covering on soil water characteristics during seasonal freeze thaw period[J]. Water Resource and Power, 2018, 36(7): 99-103.

[29] Fu Qiang, Wu Chundong, Li Tianxiao. Influence of straw mulch on soil moisture migration in northern clod region[J]. Journal of Irrigation and Drainage, 2015, 34(10): 7-10.

[30] Feng Huijun, Zhao Haoran, Zheng Xiuqing, et al. Effect of sand mulching on spatiotemporal variation of soil water content during the seasonal freezing thawing period[J]. Agricultural Research in the Arid Areas, 2019, 37(5): 40-45.

[31] Chen Junfeng, Zheng Xiuqing, Qin Zuodong, et al. Effects of maize straw mulch on spatiotemporal variation of soil profile moisture and temperature during freeze thaw period[J]. Transactions of the Chinese Society of Agricultural Engineering, 2013, 29(20): 102-110.

[32] Wang Hongli, Zhang Xucheng, Yu Xianfeng, et al. Effects of annual whole film mulching on freezing thawing characteristics, moisture, and temperature distribution of maize soil in arid area[J]. Chinese Journal of Applied Ecology, 2020, 31(4): 1146-1154.

[33] Li Hui, Jin Zhifeng, Yue Shengru. Effects of different soil surface mulching method during freezing thawing period on soil water[J]. Water Saving Irrigation, 2018, 43(10): 24-26, 32.