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Article

Effects of Straw Mulching on Near-Surface Hydrological Process and Soil Loss in Slope Farmland of Red Soil

by 1,2,3,4, 3,4, 3,4, 3,4, 1,2,* and 3,4,*
1
Key Laboratory of National Forestry and Grassland Administration on Forest Ecosystem Protection and Restoration of Poyang Lake Watershed, Nanchang 330045, China
2
College of Forestry, Jiangxi Agricultural University, Nanchang 330045, China
3
Jiangxi Academy of Water Science and Engineering, Nanchang 330029, China
4
Jiangxi Provincial Key Laboratory of Soil Erosion and Prevention, Nanchang 330029, China
*
Authors to whom correspondence should be addressed.
Water 2022, 14(21), 3388; https://doi.org/10.3390/w14213388
Received: 26 September 2022 / Revised: 19 October 2022 / Accepted: 23 October 2022 / Published: 26 October 2022
(This article belongs to the Topic Hydrology and Water Resources in Agriculture and Ecology)

Abstract

:
Slope farmland is prone to soil erosion, especially in sub/tropical regions. However, our understanding of near-surface hydrology characteristics and their controlled factors in red soil sloping farmland remains limited. Here, we conducted simulated rainfall experiments to assess the impact of rainfall pattern, straw mulching, and soil structure on near-surface hydrological processes of red soil sloping farmland of southern China. Results showed that: (1) short duration-high intensity rain caused greater surface runoff and sediment production than did long duration-low intensity rain, whereas the variation pattern of subsurface flow exhibited the opposite trend; (2) tillage behavior could weaken the surface runoff intensity and promote the development of subsurface flow; (3) straw mulching increased the water infiltration rate and associated subsurface flow production (increased by 1.33~12.71 times), and thus reduced the surface runoff production (reduced by 99.68~100%). These findings highlight the crucial roles of rainfall pattern and straw mulching in regulating the spatial distribution pattern of rainwater and suggest that straw mulching can effectively reduce soil erosion via accelerating water infiltration and subsurface flow form in slope farmland of soil erosion in southern China.

1. Introduction

Cultivated land is a scarce resource for the survival of people in various developing countries, including China [1,2]. As an important part of cultivated land, slope farmland has attracted more and more attention. However, due to unreasonable land use, the soil and water loss of slope farmland has been aggravated, making slope farmland become an important source of soil and water loss in many regions [3,4,5], which has become an ecological environment and agricultural resource problem that has attracted much attention worldwide. To ensure the normal life needs of people in hilly areas of developing countries, it is urgent to control soil erosion in sloping farmland.
Soil structure is an important factor affecting the near-surface hydrology of sloping farmland. Some scholars had preliminarily discussed the influence of soil configuration in black soil [6], purple soil [7,8] and karst topography [9] on near-surface hydrology. For example, in the report of Zhang [9], the surface runoff in the karst area after rainfall was less, and it was usually characterized by full runoff. Subsurface flow and deep leakage are important hydrological processes in the region. Zhang [6] found that in the black soil region, the soil layer was thick, the vertical stratification was obvious, the upper layer was loose, the lower layer was dense, and the infiltration performance was poor. The special soil configuration was easy to form the upper stagnant water. Long [7] found that the purple soil area had steep slope, thin soil layer, high gravel content, large porosity and strong infiltration capacity. Subsurface flow occurs in the middle and late stages of rainfall after soil saturation, and the runoff yield was large. However, the response of near-surface hydrology to rainfall caused by special tillage soil structure was still unclear. Long-term tillage of red soil slope farmland makes the surface soil loose and permeable. The bottom soil of the tillage layer was compacted by tillage equipment, which increased soil density and thus reduced soil permeability. Porosity, especially the content of macropores, is low, and the permeability is significantly lower than that of the loose plow layer, forming a typical soil structure of “upper loose-lower tight” [10]. Under sufficient precipitation and special soil configuration, red soil slope farmland makes the development of subsurface flow more active. In some extreme rainfall events, the outflow of subsurface flow even exceeds the surface runoff, which dominates the rainfall-flow process on the slope [11]. Surface runoff and subsurface flow of sloping farmland are important components of watershed runoff, and directly affect the hydrological process of the whole watershed [12,13]. Both of them play an equally important role in soil erosion.
As one of the measures to control soil erosion, straw mulching cannot only improve soil properties but also play an active role in reducing the surface erosion of sloping farmland [14,15,16]. Some scholars had preliminarily discussed the hydrodynamic process of straw mulch. Compared with bare land, straw mulching can increase surface roughness [17], significantly reduce flow velocity [18,19], reduce runoff [20,21], and reduce sediment. For example, Prosdocimi [21] reported a significant decrease in soil erosion rates due to reduced surface runoff due to straw mulching. Straw can affect the process of surface runoff and sediment production by increasing the roughness of the surface. Mulumba [22] and Guo [23] showed that straw mulching could effectively reduce surface temperature and water evaporation. Straw mulching can reduce soil bulk density and significantly promote soil water use efficiency [24]. In addition, straw mulching can also protect the soil surface from the splashing effect caused by raindrops, prevent the crusting effect of the soil surface during rainfall, and reduce the surface runoff and the amount of sediment covered by runoff [25,26]. However, few studies have considered the interaction between straw mulching on surface runoff and subsurface flow.
The southern red soil region is an important food production area in China, and it is also one of the most densely populated areas. As an important cultivated land resource in the region, slope farmland accounts for 26.3% of the cultivated land area there [27]. However, due to the unique natural conditions (such as subtropical monsoon rainfall patterns and landforms, soil parent materials, etc.) and social factors, this region has become one of the regions with serious soil and water loss in China, and agricultural development is greatly restricted. In recent years the region has used a series of means to solve the problem of soil and water loss, and has achieved remarkable phased results. However, there is still insufficient research on the response of near-surface hydrology to rainfall under straw mulching on sloping farmland in this region. Because of this, the purpose of this study is (1) to explore the influence of different rainfall patterns on near-surface hydrology and soil erosion; (2) to explore the influence of slope farmland soil structure on near-surface hydrology and soil erosion; and (3) to explore the impacts of straw mulching on near-surface hydrology and soil erosion for different rainfall patterns.

2. Materials and Methods

2.1. Study Site

The experiment was performed in the simulated rainfall hall of Jiangxi Soil and Water Conservation Ecological Science and Technology Park (115°43′42″, 29°16′55″) from July to October 2020. The science and technology park is located in the south of Dean County, Jiujiang City, Jiangxi Province. The study site is located in the small watershed of Yangou and the west bank of Boyang River in the Poyang Lake system (Figure 1). This site belongs to the subtropical monsoon climate zone with abundant rainfall. The average annual rainfall is 865.6~1807.7 mm, accounting for nearly 50% of the annual rainfall from June to October. The annual average temperature is 16.7 °C, annual sunshine hours range from 650~2100 h, the frost-free period 245~260 d, the soil parent material is Quaternary red clay, and the zonal vegetation is subtropical evergreen broad-leaved forest. The landform in the region is shallow hilly land with an elevation of 30~100 m and a slope of less than 25°. The science and technology park is located in the red soil center of China, and the terrain and soil conditions are typically representative.

2.2. Test Materials

In this experiment, we used the steel soil tank with 1.5 m × 0.5 m × 0.5 m (length × width × height) to collect surface runoff, subsurface flow, and deep leakage in soils (Figure 2). According to the field investigation, the test slope was treated as 10° [28,29], representing the slope of most red soil slope farmland. The filling soil was a typically quaternary red soil collected from the study area (Table 1). The soil was naturally dried and screened to remove plant roots and gravel for standby. A layer of 5 cm thick graded gravel was filled at the bottom of the soil tank, and a layer of geotextile was covered on the gravel to prevent the loss of the upper soil and facilitate water permeability.
In this study, the soils with the same bulk density were regarded as homogeneous soils (HoS) and filled uniformly to 5~45 cm of the soil tank. However, heterogeneous soils (HeS) were composed of two soil layers with different bulk densities. The details are exhibited in Table 2. For each treatment, soil was filled into the soil tank every 5 cm. And breaking the soil surface before filling the next layer. The soil moisture content of the soil tank test was controlled at 10 ± 1%, and the test was carried out after the completion of the soil tank filling.
Oilseed Rape (Brassica napus L.), as a common oil crop in the south of China, is widely planted in red soil sloping fields. Rapeseed leaves a large amount of straw after harvesting, which is an excellent material for straw mulching. The rape straw was taken from the rape planted in the slope farmland of the study area, and naturally dried after mature harvest. Before the experiment, the rape straw was crushed to 5~10 cm for covering. The covering amount was 10 t hm−2, and the soil tank area in this experiment was 0.75 m2. Straw laying thickness was about 3–5 cm.

2.3. Test Method

To simulate natural precipitation, this work was conducted in a rainfall hall, in which effective rainfall area, rainfall height, and rainfall evenness were 786 m2, 18 m, and 0.85, respectively. The whole rainfall hall was divided into four independent rainfall test areas, of which areas 1, 2 and 3 were the lower spraying area, and area 4 was the side spraying area. The whole process of this test was completed in zone 2, which adopts FULLJET rotary down jet nozzle. The variable range of rainfall intensity in the spraying area is 10~200 mm h−1.
Under the condition of consistent total rainfall control, two typical rainfall patterns in the southern red soil region were selected for the simulation test [30]. Rainfall pattern A was designed to simulate the rainfall with short duration-high intensity rain in summer, which lasts 1.5 h, and the rainfall intensity was 90 mm h−1. Rainfall pattern B was designed to simulate the rainfall with long duration-low intensity rain in spring, which lasted for 4.5 h and the rainfall intensity was 30 mm h−1. The designed rainfall field of this test was 3 (treatment) × 3 (repeat) × 2 (rain pattern) = 18. In the actual process of the test, there were 18 rainfalls, including 0 invalid rainfalls and 18 effective rainfalls. The test results were taken as the average of three repetitions.
In this experiment, water samples were collected every three minutes from the beginning of the rainfall and measured until the end of surface runoff. Among them, due to the mixed sediment in the surface runoff sample, the samples were weighed and filtered with a fast filter paper. The paper-wrapped sediment was put into the oven, the temperature of the oven was set to 105 °C, and the sediment was baked for more than 8 h and read after drying.

2.4. Analysis Method

All statistical analyses were performed with R version 4.1.1 [31], and the accepted significance level was set at α = 0.05. A one-way ANOVA of Tukey’s HSD comparison was used to determine the differences in the runoff, sediment yield, and subsurface flow among different treatments with the ‘agricolae’ package. Excel 2019 and Origin pro 2022 were used to process data and draw charts.

3. Results

3.1. Surface Runoff Generation Characteristics

Analysis of surface runoff start time and flow under straw mulching on red soil slope farmland is shown in Table 3. It can be seen that the surface runoff generation time of HoS (homogeneous soil) and HeS (heterogeneous soil) was similar under long duration-low intensity rain. The runoff generation time was ranked as HoS < HeS < HeS + SM from early to late. HoS and HeS began to produce runoff after 157.00 min and 160.42 min, respectively, and the HeS + SM with straw mulch did not produce surface runoff. The total surface runoff yields of HoS and HeS were 15.72 L and 9.83 L, respectively. The surface runoff of HoS was 1.6 times higher than HeS. The peak flow and average flow showed the same regularity. When the short duration-high intensity rain, the surface runoff of red soil slope land was faster, and the order was HoS < HeS < HeS + SM from early to late. HoS and HeS started runoff at 6.18 and 7.83 min after the beginning of rainfall, respectively. HeS + SM began runoff at 19.03 min. By comparing the two rainfall patterns, we can see that the short duration-high intensity rain causes early surface runoff generation, large total runoff, and high peak flow. Straw mulching significantly reduced surface runoff in red soil slopes.
It can be seen that the surface runoff intensity of HoS was greater than that of HeS under the long duration-low intensity rain (Figure 3a). Generally, the runoff intensity of Hos and HeS increased during rainfall. The runoff intensity reached its peak at the end of rainfall, and the runoff immediately ended after the end of rainfall. Differently, under short duration-high intensity rain (Figure 3b), the runoff intensity of soil tanks without straw mulching increased rapidly after runoff generation and formed superosmotic runoff. Between 20~25 min after the beginning of rainfall, the runoff intensity stabilized until the end of rainfall. Straw mulching leads to low surface runoff intensity and stable runoff yield on red soil slope.

3.2. Sediment Yield Characteristics

The soil loss analysis of red soil slope farmland under straw mulching conditions was shown in Table 4. We can know that the total erosion of HoS was 1.4 times of HeS at long duration-low intensity rain. However, due to the large surface runoff of HoS, the sediment concentration was diluted, and the sediment concentration of HoS was 0.8 times that of HeS. Under short duration-high intensity rain, the total erosion amount was 1.2 times that of HeS. The sediment concentrations of the two were close, and HoS was 0.98 times that of HeS. It is worth noting that the total amount of soil erosion caused by short duration-high intensity rain was 12.12~12.39 times that of long duration-low intensity rain, and the peak erosion reached 35.29~44.29 times. In the case of constant rainfall, short duration-high intensity rain can form greater soil erosion.
The analysis of soil loss processes caused by different rainfall patterns on sloping arable land was shown in Figure 4. We know that the erosion amount of red soil slope fluctuates with the continuous rainfall under the long duration-low intensity rain (Figure 4a). At the same rainfall time, the erosion amount generated by HoS was lower than that generated by HeS. Under short duration-high intensity rain, the trend of the HoS and HeS erosion process line was close (Figure 4b). Erosion of HoS and HeS increased rapidly from the beginning of runoff to peak in about 20 min and then decreased rapidly. The runoff intensity tends to level off until the end of the rainfall, about 50 min after the start of the rainfall.

3.3. Subsurface Flow and Deep Infiltration Characteristics

Analysis of the beginning time and flow rate of subsurface flow in red soil sloping farmland under straw mulching was shown in Table 5. It can be seen that under long duration-low intensity rain, the runoff generation time of subsurface flow of HoS and HeS was earlier than that of surface runoff. The subsurface flow of HoS was 14.5 min earlier than that of surface runoff, and the subsurface flow of HeS was 19.19 min earlier than that of surface runoff. The total flow in soil from high to low was HeS + SM > HeS > HoS, but the peak flow production was HeS + SM > HoS > HeS. Under long duration-low intensity rain, the beginning time of HoS leakage (40 cm) runoff was close to that subsurface flow. However, the leakage of HeS and HeS + SM was significantly different from the runoff generation time of subsurface flow. The time of subsurface flow and leakage of HeS + SM was earlier than that of HeS. We found that the total runoff showed HeS + SM > HeS > HoS in the long duration-low intensity rain. This indicates that the flow rate was positively correlated with the flow time. Under short duration-high intensity rain, the runoff generation time of subsurface flow was later than that of surface flow, and the runoff generation time from early to late was HoS < HeS < HeS + SM, which was opposite to that under long duration-low intensity rain. The total flow of subsurface flow was inversely proportional to the runoff generation time, which was HoS < HeS < HeS + SM. Straw mulch had a great influence on leakage. The leakage runoff of the soil tank covered by straw mulch started early and the runoff was large.
The response process of subsurface flow to different rainfall patterns in red soil sloping farmland under straw mulching was shown in Figure 5. We can see that the HeS + SM flow generation time was the earliest (Figure 5a). With continuous rainfall, the runoff intensity was increased. Runoff intensity was proportional to time. The runoff intensity was proportional to time until the peak intensity is reached at the end of rainfall, and then rapidly decreased to the end of runoff. The runoff generation time of HoS was close to that of HeS. After HoS began to produce runoff, the runoff intensity increased rapidly, reached the peak at 169.50 min, and then decreased rapidly. The runoff stopped at 208.5 min. The runoff intensity increased rapidly after the beginning of HeS runoff, remained stable at about 180 min, and gradually decreased to the end of rainfall after 210 min. Under the condition of short duration-high intensity rain, the runoff intensity of HoS and HeS was higher than that of HeS + SM at the beginning of runoff generation (Figure 5b). The runoff generation time of HeS + SM was relatively late. With continuous rainfall, the runoff intensity of subsurface flow increased and reached the peak intensity at the end of rainfall.

4. Discussion

4.1. Effects of Rainfall Pattern on Near-Surface Hydrological Process and Soil Loss

In this study, the surface runoff generated by short duration-high intensity rain in uncovered sloping farmland was 5.18~6.79 times that of long duration-low intensity rain, and soil erosion was 12.12~14.39 times as much. For short duration-high intensity rain, the surface runoff accounted for 66~80% of the total rainfall water, and the surface runoff caused by long duration-low intensity rain accounted for only 10~16% of the rainfall water (Figure 6). Previous [32,33] studies showed that short duration-high intensity rain is an important rainfall pattern that causes erosion in various regions compared to long duration-low intensity rain. Ma [34] found that the mean runoff depth of short duration-high intensity rain was 3.4 times that of long duration-low intensity rain. Short duration-high intensity rain is the main pattern of rainfall that causes runoff development on purple soil slopes. Fang [32] analyzed natural rainfall and found that the total runoff caused by short duration-high intensity rain was the highest among all rainfall patterns in karst areas. Ma [33] reported that the rill erosion of red soil slope farmland occurred in the 33rd minute under the condition of heavy rain and heavy rain, and in the 160th minute under the condition of light rain and heavy rain. Generally, short duration-high intensity rain in a certain period rainfall, more than surface soil moisture infiltration rate to form surface runoff. The water not absorbed by the soil forms surface runoff, which takes away the surface soil and leads to soil erosion. Therefore, short duration-high intensity rain is more likely to cause soil erosion than long duration-low intensity rain under the same value of rainfall.
Different rainfall patterns have a great influence on subsurface flow beginning time and runoff yield. Specifically, the subsurface flow of long duration-low intensity rain started earlier than that of short duration-high intensity rain. Moreover, the subsurface flow produced by long duration-low intensity rain was 1.80~4.43 times that of short duration-high intensity rain in uncovered sloping farmland. Long duration-low intensity rain produced a subsurface flow of 2~4% of total rainfall, while short duration-high intensity rain produced 0~2% (Figure 6). We believe that in long duration-low intensity rain, the rainfall intensity per unit time is small, and the water has sufficient time to infiltrate, thus forming subsurface flow. In short duration-high intensity rain, the infiltration rate of surface soil was lower than that of rainfall intensity, forming infiltration excess runoff [35]. Moreover, short duration-high intensity rain forms surface crusts after raindrops hit the surface soil [36,37], further reducing the soil infiltration rate and subsurface flow. This is consistent with most previous studies [38]. These findings indicate that long duration-low intensity rain is more likely to promote the development of subsurface flow than short duration-high intensity rain.

4.2. Effect of Soil Structure on Near-Surface Hydrological Process and Soil Loss

In red soil slope farmlands, soil structure is an important factor affecting surface runoff and erosion [39]. Our results showed that the surface runoff generated by HeS (heterogeneous) was lower than that done by HoS (homogeneous), regardless of rainfall pattern. Because the surface infiltration rate of soil with heterogeneous is higher than that of homogeneous soil. Part of the water was absorbed by the surface soil infiltration, thereby reducing the generation of surface runoff. This is consistent with previous research results [40]. Nanda [40] report that the spatial heterogeneity of soil properties affects the spatial distribution of runoff. Relatedly, less surface runoff can cause less erosion. This is consistent with our results that HeS has lower surface soil erosion than HoS. These phenomena indicate that the soil structure of red soil slope farmland can effectively reduce the yield of surface runoff and weaken the surface erosion caused by rainfall.
The subsurface flow is also affected by the soil structure. Different from surface runoff, the subsurface flow of HeS was 2.53~6.23 times of HoS under two rainfall patterns. Under HeS conditions, the proportion of subsurface flow in rainfall water increased by about 2%. Soil structure increases the flow of subsurface flow, which was consistent with previous studies [41]. Soil heterogeneity caused by long-term tillage of sloping farmland can effectively reduce the intensity of surface runoff [42]. When the water infiltrates into the heterogeneous soil, it encounters the plow pan with poor permeability, forming a lateral subsurface flow. This will reduce the water pressure in the surface soil, increase the water infiltration rate and reduce the surface runoff. Aldo [41] report that heterogeneity is more sensitive to rainfall inputs. The increase of subsurface flow and saturation is faster than that of a homogeneous case. In summary, the soil structure of red soil slope farmland can increase the water infiltration rate and increase the proportion of subsurface flow in the overall water. Therefore, soil structure can affect near-surface hydrology, reduce soil erosion, and achieve the effect of water and fertilizer conservation.

4.3. Effect of Straw Mulching on Near-Surface Hydrological Process and Soil Loss

Straw mulching is an effective means of dealing with soil erosion caused by rainfall. Straw mulching reduced 99.7% (Long duration-low intensity rain)~100% (Short duration-high intensity rain) surface runoff and 100% surface erosion under different rainfall patterns, respectively. Compared with bare land, surface runoff and erosion in straw mulching experiments decreased significantly, which was similar to the results of several authors [43,44,45,46]. Misagh [43] found that a higher straw application rate would produce less runoff and reduce soil erosion. Wang [44] also found that straw mulching had a significant effect on the average infiltration rate, cumulative runoff and cumulative sediment yield on the slope. We believe that the physical and biochemical properties of surface soil change when the straw is covered on sloping farmland. Straw mulching can reduce the impact of rainfall on surface soil and reduce surface crust. Straw mulching can also reduce surface soil temperature [47], decrease soil bulk density [48,49], increase soil porosity [50] and increase soil water storage. For example, Liu [47] proposed that soil porosity gradually increased with the continuous coverage of straw. Increasing soil porosity can improve soil infiltration, thus affecting surface runoff and subsurface flow. These results suggest that straw mulching can regulate the formation of surface runoff and reduce surface soil erosion.
In this study, the subsurface flow was significantly affected by straw mulching (Table 4). Specifically, in long duration-low intensity rain, the initial runoff time of subsurface flow caused by straw mulching was 39.73 min earlier than that without mulching, and the total subsurface flow runoff increased by 33.42%. After straw mulching, the proportion of total precipitation in subsurface flow runoff increased by 1~25%, and the amount of deep leakage also increased by 6~41% (Figure 6). These findings indicate that straw mulching can effectively promote the development of subsurface flow [38]. The report of Gao [46] suggested that straw mulching could significantly increase subsurface flow under various rainfall intensities. Duan [38] reported that straw mulching significantly reduced surface runoff and significantly increased subsurface flow at a depth of 30 cm. Different from the previous research results, in short duration-high intensity rain, straw mulching increased the total amount of subsurface flow runoff to 12.71 times, but the initial runoff time-lagged 10.02 min. We believe that heavy rainfall has compacted and splashed the surface of sloping farmland without straw mulching in this experiment. This leads to the change of surface micro-topography, and some surface soil forms a crust effect. Therefore, a large amount of water carried by rainfall cannot be infiltrated, forming runoff on the surface. Due to the large surface runoff water potential, the water rapidly infiltrates the large gap to form a preferential flow, and the subsurface flow is formed at the change of soil structure. Straw mulching reduced the splash erosion of raindrops on surface soil, resulting in loose surface soil and a high infiltration rate. Moreover, straw mulching reduced the flow velocity of surface runoff and made it infiltrate nearby. The straw mulching treatment made the surface soil moisture reach saturation before the formation of subsurface flow, resulting in the formation of subsurface flow later. Straw mulching enables the water carried by short duration-high intensity rain to be fully fixed by the surface soil. After the surface soil is saturated, subsurface flow is formed to recharge groundwater resources. This plays a positive role in water and fertilizer conservation and reduces soil erosion in slope farmland.
This study provides theoretical support for the application of straw mulching on red soil slope farmland. The protective effect of rape straw mulching on the surface soil of red soil slope farmland under short duration-high intensity rain was proposed, which was conducive to the popularization and application of this measure. However, the conclusion of this study was only obtained under the condition of single rape straw coverage and slope, which may vary with different coverage and slope. It will be the focus of our future research to select different coverage and find the optimal straw coverage of red soil slope farmland to expand the application scope and practicability of the research results.

5. Conclusions

In this study, the effects of rainfall pattern, soil structure, and straw mulching on near-surface hydrology and erosion were investigated in the sloping cropland of red soil. The main conclusions are as follows: (1) The intensity of surface runoff formed by short duration-high intensity rain is greater than that of long duration-low intensity rain, and the surface soil is more eroded. At the same time, short duration-high intensity rain is not conducive to the development of subsurface flow and cannot make full use of the water brought by rainfall; (2) Under the two rainfall patterns, the surface runoff intensity of HeS (heterogeneous) is smaller than that of HoS (homogeneous), while the subsurface flow runoff intensity is the opposite. This shows that the soil structure of red soil slope farmland can affect the development process of near surface hydrology, increase the infiltration of rainfall water, and reduce the surface runoff and erosion of the slope; (3) After mulching with rape straw, the intensity of surface runoff decreased significantly, and the intensity of subsurface flow increased significantly. The improvement of coverage on short duration-high intensity rain is particularly evident. Straw mulching can make the precipitation water fully fixed by the surface soil, which is conducive to the absorption and utilization of water by crops, and reduce the loss of soil. These findings will help to understand the impact of rainfall on the near-surface hydrology of sloping farmland in red soil and provide a theoretical basis for production practice.

Author Contributions

Study design: X.G. and J.Y.; Investigation: L.Y., L.P. and X.Z.; Data analysis and mapping: L.Y. and L.P.; Funding acquisition: J.Y.; Writing—original: L.Y. and J.D.; Writing—editing: X.G. and J.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the project of National Natural Science Foundation of China (41761065), Supported by the Cultivation Plan for Reserved Project of National Science and Technology Award (Grants No. 20212AEI91011) and Key Science and Technology Project of Jiangxi Province (20213AAG01012; 2022KSG01001).

Data Availability Statement

The data reported in this study are available on request from the corresponding authors. The data are not publicly available yet due to the authors are writing some other papers by mining these data.

Conflicts of Interest

The authors declare no conflict of interests.

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Figure 1. Location map of test area (a) Location of Jiangxi Province in China; (b) Location of De’an County in Jiangxi Province; (c) The location relationship between the test site and Yangou watershed, De’an County and Poyang Lake.
Figure 1. Location map of test area (a) Location of Jiangxi Province in China; (b) Location of De’an County in Jiangxi Province; (c) The location relationship between the test site and Yangou watershed, De’an County and Poyang Lake.
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Figure 2. Experimental demonstration and soil tank schematic. (a) Uncovered soil tank. (b) Soil tanks during rainfall experiment. (c) Straw–covered soil tank. (d) Schematic diagram of steel soil tank.
Figure 2. Experimental demonstration and soil tank schematic. (a) Uncovered soil tank. (b) Soil tanks during rainfall experiment. (c) Straw–covered soil tank. (d) Schematic diagram of steel soil tank.
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Figure 3. Surface runoff process under different rainfall patterns (a) Long duration-low intensity rain; (b) Short duration-high intensity rain. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch.
Figure 3. Surface runoff process under different rainfall patterns (a) Long duration-low intensity rain; (b) Short duration-high intensity rain. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch.
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Figure 4. Surface sediment production process under different rain patterns (a) Long duration-low intensity rain; (b) Short duration-high intensity rain. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch.
Figure 4. Surface sediment production process under different rain patterns (a) Long duration-low intensity rain; (b) Short duration-high intensity rain. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch.
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Figure 5. Subsurface flow process under different rainfall patterns (a) Long duration-low intensity rain; (b) Short duration-high intensity rain. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch.
Figure 5. Subsurface flow process under different rainfall patterns (a) Long duration-low intensity rain; (b) Short duration-high intensity rain. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch.
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Figure 6. Surface runoff and subsurface flow under different rainfall patterns. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch. (The proportion is less than 1%, and the figure is not marked).
Figure 6. Surface runoff and subsurface flow under different rainfall patterns. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch. (The proportion is less than 1%, and the figure is not marked).
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Table 1. Basic physical and chemical properties of soils.
Table 1. Basic physical and chemical properties of soils.
Sand/(%)Silt/(%)Clay/(%)pHOrganic Matter/(g kg−1)
13.70053.05533.2455.53313.24
Note: Sand (2.0 mm ≥ D > 0.02 mm). Silt (0.02 mm ≥ D > 0.002 mm). Clay (D < 0.002 mm).
Table 2. Backfilling bulk density of soil tank.
Table 2. Backfilling bulk density of soil tank.
Soil Depth/(cm)HoS/(g cm−3)HeS/(g cm−3)HeS + SM/(g cm−3)
0~151.101.101.10
15~401.101.451.45
Note: HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch.
Table 3. Effect of straw mulching on surface runoff of Red Soil Sloping Farmland.
Table 3. Effect of straw mulching on surface runoff of Red Soil Sloping Farmland.
Rain PatternTest TreatmentRunoff Generation Time/(min)Total Flow/(L)Peak Flow/(mL)Average Flow/(mL)
Long duration
-low intensity
HoS157.00 ± 4.25 a15.72 ± 1.60 a740.00 ± 3.00 a413.71 ± 21.05 a
HeS160.42 ± 3.35 a9.83 ± 1.63 b500.00 ± 45.00 b265.54 ± 7.65 b
HeS + SM/000
Short duration
-high intensity
HoS6.18 ± 0.03 c81.41 ± 3.82 a3300.00 ± 155.00 a3015.19 ± 127.41 a
HeS7.83 ± 0.31 b66.70 ± 7.52 b2800.00 ± 55.00 b2382.14 ± 90.60 b
HeS + SM19.03 ± 1.20 a0.21 ± 0.02 c18.00 ± 5.00 c9.22 ± 0.84 c
Note: For the same column, different lowercase letters indicate significant differences among different treatments under the same rain pattern (p < 0.05). ± denotes standard deviation. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch.
Table 4. Effect of straw mulching on soil loss in red soil sloping farmland.
Table 4. Effect of straw mulching on soil loss in red soil sloping farmland.
Rain PatternTest TreatmentSediment Concentration (g L−1)Total Sediment Yield (g)Peak Sediment Yield (g)Average Sediment Yield (g)
Long duration
-low intensity
HoS2.58 ± 0.06 a40.43 ± 5.94 a1.54 ± 0.05 a1.19 ± 0.041 a
HeS3.23 ± 0.19 a28.25 ± 3.17 b1.19 ± 0.03 a0.94 ± 0.039 a
HeS + SM0000
Short duration
-high intensity
HoS5.96 ± 0.23 b490.06 ± 20.08 a54.35 ± 1.40 a17.50 ± 1.07 a
HeS6.09 ± 0.02 a406.52 ± 10.70 a52.70 ± 0.95 b14.52 ± 0.50 b
HeS + SM0000
Note: For the same column, different lowercase letters indicate significant differences among different treatments under the same rain pattern (p < 0.05). ± denotes standard deviation. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch.
Table 5. Effects of straw mulching on subsurface flow and deep leakage in red soil sloping farmland.
Table 5. Effects of straw mulching on subsurface flow and deep leakage in red soil sloping farmland.
Rain PatternTest TreatmentSubsurface FlowDeep Leakage
Runoff Generation Time (min)Lag Time Compared with the Surface (min)Total Flow (L)Peak Flow (mL)Runoff Generation Time (min)Lag Time Compared with the Surface (min)Total Flow (mL)Peak Flow (mL)
Long duration-low intensity HoS142.50 ± 1.75 a−14.50 ± 2.50 a1.55 ± 0.09 c175.00 ± 7.00 a141.50 ± 4.95 b−15.5 ± 0.7 b34.43 ± 2.30 a1467.00 ± 75.00 a
HeS141.23 ± 1.52 a−19.19 ± 1.83 a3.92 ± 0.19 b152.00 ± 11.00 b168.75 ± 3.67 a8.33 ± 0.32 a23.24 ± 3.20 b480.00 ± 56.00 b
HeS + SM101.50 ± 2.74 b/5.23 ± 0.30 a180.00 ± 10.00 a161.30 ± 2.12 a/29.03 ± 3.55 ab600.00 ± 60.00 b
Short duration-high intensity HoS10.85 ± 0.37 c4.67 ± 0.34 b0.35 ± 0.04 c130.00 ± 5.00 b92.12 ± 11.28 a85.94 ± 11.25 a1.35 ± 0.11 b30.00 ± 5.00 b
HeS13.00 ± 0.80 b5.17 ± 0.49 a2.18 ± 0.14 b140.00 ± 4.00 b////
HeS + SM23.02 ± 1.28 a3.99 ± 0.08 c27.71 ± 0.93 a1790.00 ± 120.00 a39.65 ± 1.75 b20.62 ± 0.55 b41.42 ± 5.03 a1280.00 ± 80.00 a
Note: For the same column, different lowercase letters indicate significant differences among different treatments under the same rain pattern (p < 0.05). ± denotes standard deviation. HoS, Homogeneous soil. HeS, Heterogeneous soil. HeS + SM, Heterogeneous soil + Straw mulch.
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Yang, L.; Duan, J.; Peng, L.; Zhang, X.; Guo, X.; Yang, J. Effects of Straw Mulching on Near-Surface Hydrological Process and Soil Loss in Slope Farmland of Red Soil. Water 2022, 14, 3388. https://doi.org/10.3390/w14213388

AMA Style

Yang L, Duan J, Peng L, Zhang X, Guo X, Yang J. Effects of Straw Mulching on Near-Surface Hydrological Process and Soil Loss in Slope Farmland of Red Soil. Water. 2022; 14(21):3388. https://doi.org/10.3390/w14213388

Chicago/Turabian Style

Yang, Luyang, Jian Duan, Lang Peng, Xinyin Zhang, Xiaomin Guo, and Jie Yang. 2022. "Effects of Straw Mulching on Near-Surface Hydrological Process and Soil Loss in Slope Farmland of Red Soil" Water 14, no. 21: 3388. https://doi.org/10.3390/w14213388

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