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1.
Data on surface runoff and soil loss on gentle slopes with vineyards are analysed. Using a rainfall simulator, 22 rainstorms with varied intensities from 30 to 117.5 mm h−1 and return periods from 2 to 127 years were reproduced. The experimental plots were installed on vineyards planted in straight rows and oriented with the slope direction having a mean gradient of 3.8°. The texture of soils was loamy, with a very heterogeneous surface gravel cover. Values of measured surface runoff varied from 7.2 mm h−1 for low rainfall intensities (30 mm h−1) and short return periods (2 years) to 41.9 mm h−1 with simulation experiments of higher rainfall intensity (104 mm h−1) and long return periods (68 years). Runoff increased linearly with rainfall intensity resulting in soil losses that also increased with rainfall intensity (18.2 g m−2 h−1 with storms of 30 mm h−1, and 93.2 g m−2 h−1 with storms of 104 mm h−1); however, r2 explains only 36% of the variance. It was necessary to add other factors to improve the coefficient of determination (0.74; p = 0.001) and the predictive function of the equation. These variables were rainfall intensity, kinetic energy of the storm, runoff, soil resistance to drop detachment, surface gravel cover, and gradient. The equation obtained was validated with the USLE-M. In comparison with similar experiments in other regions, the results obtained for soil loss were very moderate, especially those caused by rainstorms of intermediate and low intensity.  相似文献   

2.
An  Juan  Zhang  Yunqi  Wang  Yueyue 《Journal of Soils and Sediments》2020,20(4):2192-2206
Purpose

Intra-storm temporal distributions of rainfall intensity (storm patterns) greatly affect soil erosion process within flat tillage systems, but limited information is available about its influence on the distribution characteristics of soil aggregate, especially within contour ridge system.

Materials and methods

In this study, a laboratory study of 12 rainfall simulation experiments was conducted to analyze the loss characteristic of 16 sizes aggregate in eroded sediment within contour ridge system under the rising, falling, rising–falling, and falling–rising patterns. All patterns included three rainfall intensities, 30, 60, and 90 mm h?1, and comprised the same rainfall amount and kinetic energy.

Results and discussion

The results showed that storm patterns showed significant influence on soil aggregate loss. The rising–falling, falling–rising, and falling pattern had 1.43, 1.11, and 1.04 times soil aggregate loss greater than the rising pattern, respectively. Differences in size distribution of soil aggregate among storm patterns mainly concentrated on the most eroded size of microaggregate, especially 50–100 μm fraction. An intensity of 30 mm h?1 made the greatest contribution of 100.87%–511.93% to the diversity of soil aggregate loss following the storm pattern simulations relative to 60 and 90 mm h?1 intensities, likely resulting from erosion process, soil aggregate detachment, and runoff transport abilities from 30 mm h?1 intensity varying within storm pattern duration. The occurring periods of rainfall intensity significantly affected the loss of each size aggregate and showed the most obvious influence on 50–100 μm aggregate. Effects of storm pattern and rainfall intensity occurring periods were more pronounced with the increase of aggregate size at the macro-aggregate scale. Contour failure was easily to occur under the most prevalent storm pattern—falling and rising–falling patterns—which comprised 59.44% of soil aggregate loss.

Conclusions

Results recommended that more attention should be given to contour ridge stability, especially under falling and rising–falling patterns. Incorporating contour failure and the occurring context of rainfall intensity into the erosion model could successfully simulate soil aggregate loss characteristics, especially small-sized aggregates.

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3.
Purpose

Characterizations of soil aggregates and soil organic carbon (SOC) losses affected by different water erosion patterns at the hillslope scale are poorly understood. Therefore, the objective of this study was to quantify how sheet and rill erosion affect soil aggregates and soil organic carbon losses for a Mollisol hillslope in Northeast China under indoor simulated rainfall.

Materials and methods

The soil used in this study was a Mollisol (USDA Taxonomy), collected from a maize field (0–20 cm depth) in Northeast China. A soil pan with dimensions 8 m long, 1.5 m wide and 0.6 m deep was subjected to rainfall intensities of 50 and 100 mm h?1. The experimental treatments included sheet erosion dominated (SED) and rill erosion dominated (RED) treatments. Runoff with sediment samples was collected during each experimental run, and then the samples were separated into six aggregate fractions (0–0.25, 0.25–0.5, 0.5–1, 1–2, 2–5, >?5 mm) to determine the soil aggregate and SOC losses.

Results and discussion

At rainfall intensities of 50 and 100 mm h?1, soil losses from the RED treatment were 1.4 and 3.5 times higher than those from the SED treatment, and SOC losses were 1.7 and 3.8 times greater than those from the SED treatment, respectively. However, the SOC enrichment ratio in sediment from the SED treatment was 1.15 on average and higher than that from the RED treatment. Furthermore, the loss of <?0.25 mm aggregates occupied 41.1 to 73.1% of the total sediment aggregates for the SED treatment, whereas the loss of >?0.25 mm aggregates occupied 53.2 to 67.3% of the total sediment aggregates for the RED treatment. For the organic carbon loss among the six aggregate fractions, the loss of 0–0.25 mm aggregate organic carbon dominated for both treatments. When rainfall intensity increased from 50 to 100 mm h?1, aggregate organic carbon loss increased from 1.04 to 5.87 times for six aggregate fractions under the SED treatment, whereas the loss increased from 3.82 to 27.84 times for six aggregate fractions under the RED treatment.

Conclusions

This study highlights the effects of sheet and rill erosion on soil and carbon losses at the hillslope scale, and further study should quantify the effects of erosion patterns on SOC loss at a larger scale to accurately estimate agricultural ecosystem carbon flux.

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4.
Herbicides released through agricultural activities to surface waters and drinking water systems represent a risk to human and environmental health, as well as a cost to municipalities for removal. This study focuses on the viability of glyphosate tolerant cropping systems as an alternative to atrazine-based systems, and the impact of tilling historically no-till ground on the runoff pollution potential of these systems. Variable intensity field rainfall simulations were performed on 2 m long × 1 m wide plots within a field in first-year disk and harrow following no-till (CT), and within a long-term no-tilled (NT) field, both treated with atrazine and glyphosate according to label. Rainfall sequence was: 50 mm h−1 for 50 min followed by 75 mm h−1 for 15 min, 25 mm h−1 for 15 min, and 100 mm h−1 for 15 min. Runoff was collected at regular time intervals during two simulated rainfall events and analyzed for herbicide concentration, sediment content, and volume. Maximum glyphosate concentration in runoff was 233 μg L−1 for NT and 180 μg L−1 for CT (approximately 33% and 26% of the maximum contaminant limit (MCL) for glyphosate (700 μg L−1), respectively, while maximum atrazine concentrations in runoff was 303 μg L−1 for NT and 79 μg L−1 for CT (approximately 100 times and 26 times the atrazine MCL (3 μg L−1)). Atrazine concentration and loading were significantly higher in runoff from NT plots than from CT plots, whereas glyphosate concentration and loading were impacted by tillage treatment to a much lesser degree. Results suggest that glyphosate-based weed management may represent a lower drinking water risk than atrazine-based weed management, especially in NT systems.  相似文献   

5.
Rill is a major type of erosion on upland slopes. Continuous rainfall is commonly used in laboratory studies on rill erosion despite the fact the rainfall was often discontinuous in the field; this is particularly true in the Chinese Loess Plateau. This study compares rill erosion under continuous and intermittent rainfalls by using laboratory experiments. The experiments include two rainfall‐intensity treatments (90 and 120 mm h−1) and two rainfall‐pattern treatments (continuous and intermittent). The results indicate that rill formation had a significant effect on runoff and sediment concentration. For continuous and intermittent rainfall at the rainfall intensity of 90 mm h−1, the mean sediment concentrations were 1·91 and 1·73 times after rill initiation than those before rill initiation, respectively, and the rill erosion accounted for 75·5% and 77·7% of runoff duration, respectively. For continuous and intermittent rainfall at the rainfall intensity of 120 mm h−1, the mean sediment concentrations after rill initiation were 1·38 and 1·32 times that those before rill initiation, respectively, and the rill erosion represented 88·7% and 78·8% of the total runoff duration, respectively. We observed sediment sorting under all treatments; however, the low rainfall intensity boosted but the high rainfall intensity lowered the clay fraction; in contrast, the sorting remained roughly the same between the rainfall‐pattern treatments. The runoff velocity also affected the sediment sorting. Our empirical results indicated the important significance of the rainfall intermittence in predicting rill erosion. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

6.
S. Assouline  M. Ben-Hur 《CATENA》2006,66(3):211-220
Soil erosion during rainfall is strongly affected by runoff and slope steepness. Runoff production is drastically increased when a seal is formed at the soil surface during rainfall. Therefore, a complex interaction exists between soil erosion and surface sealing. In this study, the dynamics of interrill erosion during seal formation is studied under different simulated rainfall and slope conditions. A sandy soil was exposed to 70 mm of rainfall at two intensities, 24 mm h− 1 and 60 mm h− 1, and five slope gradients, from 5% to 25%. Infiltration, runoff and soil loss rates were monitored during rainfall. Final infiltration rates increased with slope gradient at both rainfall intensities, this effect being stronger for the higher intensity. Cumulative runoff at the end of the rainfall event was lower as slopes were steeper, while an opposite trend was obtained for soil loss. For the 5% and the 9% slopes, the sediment concentration in runoff reached quickly a stable value during the whole rainfall event, while it reached a peak value before declining for the higher slopes. The peak value and its timing were rainfall intensity dependent. Soil erodibility during seal formation was evaluated using two empirical multiplication-of-factors type models. It seems that slope and rainfall erosivity are accounted for only partly in these models. For mild slope gradients below 9%, the value of Ki estimated by means of the two expressions becomes practically constant shortly after runoff apparition. Consequently, the estimates resulting from this type of expressions remain valuable from the practical point of view.  相似文献   

7.
土质道路经长期碾压产生了大量浮土,加剧了道路侵蚀.本文通过人工模拟降雨试验,研究不同雨强及坡度条件下薄层1.0 cm和厚层4.0 cm浮土土质道路的产流产沙特征.根据侵蚀物质的差异,将浮土道路侵蚀过程分为单独浮土侵蚀阶段和浮土、道路混合侵蚀阶段.结果表明:(1)浮土侵蚀阶段、混合侵蚀阶段薄层浮土平均径流率为厚层浮土的1...  相似文献   

8.
Soil cover and rainfall intensity (RI) are recognized to have severe impacts on soil erosion and an interaction exists between them. This study investigates the effect of rainfall intensity (RI) and soil surface cover on losses of sediment and the selective enrichment of soil organic carbon (SOC) in the sediment by surface runoff. A field rainfall simulator was used in the laboratory to produce 90 min rainfall events of three rainfall intensities (65, 85 and 105 mm h− 1) and four cover percentages (0%, 25%, 50% and 75%) on soil material at 9% slope. A strong negative exponential relation was observed between cover percentage and RI on sediment loss under 85 and 105 mm h− 1 of rain, while under RI of 65 mm h− 1, the highest sediment loss was observed under 25% cover. Overall, higher RI and lower cover produced higher sediment and consequently higher nutrient loss, but resulted in a lower SOC enrichment ratio (ERSOC) in the sediment. The amount of runoff sediment rather than the ERSOC in the sediment was the determinant factor for the amount of nutrients lost. The values of ERSOC were high and positively correlated with the ER values of particles smaller than 20 µm (p < 0.01). Although the sediment contained substantially more fine fractions (fine silt and clay, < 20 µm), the original soil and runoff sediment were still of the same texture class, i.e. silt clay loam.  相似文献   

9.
The effectiveness of a surface cover material (e.g. geotextiles, rock fragments, mulches, vegetation) in reducing runoff and soil erosion rates is often only assessed by the fraction of the soil surface covered. However, there are indications that soil structure has important effects on the runoff and erosion-reducing effectiveness of the cover materials. This study investigates the impact of soil pre-treatment (i.e. fine tilth versus sealed soil surface) on the effectiveness of biological geotextiles in increasing infiltration rates and in reducing runoff and interrill erosion rates on a medium and steep slope gradient. Rainfall was simulated during 60 min with an intensity of 67 mm h−1 on an interrill erosion plot having two slope gradients (i.e. 15 and 45%) and filled with an erodible sandy loam. Five biological and three simulated geotextiles with different cover percentage were tested on two simulated initial soil conditions (i.e. fine tilth and sealed soil surface). Final infiltration rates on a sealed soil surface (7.5–18.5 mm h−1) are observed after ca. 10 min of rainfall compared to ca. 50 min of rainfall on an initial seedbed (16.4–56.7 mm h−1). On the two tested slope gradients, significantly (α = 0.05) smaller runoff coefficients (RC) are observed on an initial seedbed (8.2% < RC < 59.8%) compared to a sealed soil surface (75.7% < RC < 87.0%). On an initial seedbed, decreasing RC are observed with an increasing simulated geotextile cover. However, on an initial sealed soil surface no significant effect of simulated geotextile cover on RC is observed. On a 15% slope gradient, calculated b-values from the mulch factor equation equalled 0.054 for an initial fine tilth and 0.022 for a sealed soil surface, indicating a higher effectiveness of geotextiles in reducing interrill erosion on a fine tilth compared to a sealed soil surface. Therefore, this study demonstrates the importance of applying geotextiles on the soil surface before the surface tilth is sealed due to rainfall. The effect of soil structure on the effectiveness of a surface cover in reducing runoff and interrill erosion rates, as indicated by the results of this study, needs to be incorporated in soil erosion prediction models.  相似文献   

10.
The effect of raindrop temperatures on runoff generation and erosion on clayey soil was investigated in sprinkling experiments with a laboratory rotating disk rain simulator. The experiments were applied to Rhodoxeralt (Terra Rossa) soil with two pre‐prepared moisture contents: hygroscopic and field capacity. For each moisture content, three rainfall temperatures were applied: 2, 20, and 35 °C. Erosion was generally lower in the pre‐wetted soil than in the dry soil (12.5 and 24.4 g m−2 per 40 mm of rain, respectively). Whereas there was no significant effect of raindrop temperature on the dry soil, the soil that was pre‐moistened to field capacity was affected by rainwater temperature: runoff and erosion were high when the temperature difference between rainfall and soil surface was high, and sediment yields were 13·9, 5·2, and 18·3 g m−2 per 40 mm of rain, for rain temperature of 2, 20, and 35 °C, respectively. It is reasonable to conclude that thermophoresis caused by thermal gradients within the soil solution reduces the stability of aggregates and then increases the soil losses. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

11.
Conservation tillage practices are commonly used to reduce erosion; however, in fields that have been in no-tillage (NT) for long periods, compaction from traffic can restrict infiltration. Rotational tillage (RT) is a common practice that producers use in the central corn-belt of the United States, and could potentially reduce soluble nutrient loads to surface waters. The objectives of this study were to determine the first year impacts of converting from long-term NT to (RT) on N and P losses through runoff. Plots (2 m × 1 m) were constructed in two fields that had been in NT corn–soybean rotation for the previous 15 years. One field remained in NT management, while RT was initiated prior to planting corn in the other field using a soil finisher. Variable-intensity rainfall simulations occurred before and after fertilization with urea (224 kg N ha−1) and triple superphosphate (112 kg P ha−1). Rainfall was simulated at (1) 50 mm h−1 for 50 min; (2) 75 mm h−1 for 15 min; (3) 25 mm h−1 for 15 min; (4) 100 mm h−1 for 15 min. Runoff volumes and nutrient (NH4-N, NO3-N and dissolved P [DP]) concentrations were greater from the NT field than the RT field before and after fertilization.Dissolved P concentrations in runoff prior to fertilization were greater during the 50 mm h−1 rainfall period (0.09 mg L−1) compared to the other periods (0.03 mg L−1). Nutrient concentrations increased by 10–100-fold when comparing samples taken after fertilization to those taken prior to fertilization. Nutrient loads were greater prior to and after fertilization from the NT treatment. Prior to fertilization, NT resulted in 83 g ha−1 greater NH4-N and 32.4 g ha−1 greater dissolved P losses than RT treatment. After fertilization, NT was observed to lose 5.3 kg ha−1 more NH4-N, 1.3 kg ha−1 more NO3-N, and 2.4 kg ha−1 more dissolved P than RT. It is typically difficult to manage land to minimize P and N losses simultaneously; however, in the short term, tillage following long-term NT resulted in lowering the risk of transport of soluble N and P to surface water.  相似文献   

12.
The Tibetan Plateau (TP) in China has been experiencing severe water erosion because of climate warming. The rapid development of weather station network provides an opportunity to improve our understanding of rainfall erosivity in the TP. In this study, 1-min precipitation data obtained from 1226 weather stations during 2018–2019 were used to estimate rainfall erosivity, and subsequently the spatial-temporal patterns of rainfall erosivity in the TP were identified. The mean annual erosive rainfall was 295 mm, which accounted for 53% of the annual rainfall. An average of 14 erosive events occurred yearly per weather station, with the erosive events in the wet season being more likely to extend beyond midnight. In these cases, the precipitation amounts of the erosive events were found to be higher than those of the daily precipitations, which may result in implicit bias as the daily precipitation data were used for estimating the rainfall erosivity. The mean annual rainfall erosivity in the TP was 528 MJ mm·ha?1·h?1, with a broader range of 0–3402 MJ mm·ha?1·h?1, indicating a significant spatial variability. Regions with the highest mean annual rainfall erosivity were located in the forest zones, followed by steppe and desert zones. Finally, the precipitation phase records obtained from 140 weather stations showed that snowfall events slightly impacted the accuracy of rainfall erosivity calculation, but attention should be paid to the erosion process of snowmelt in the inner part of the TP. These results can be used as the reference data for soil erosion prediction in normal precipitation years.  相似文献   

13.
In Galicia (northwestern Spain), cultivated soils developed on schists from the Ordenes series are susceptible to surface degradation, mostly when soil organic content decreases. Therefore, management systems that protect the soil and increase its organic-matter content should also improve its quality. However, tillage practices may cause crusting. Degraded soil surface conditions favor surface runoff, thus enhancing nutrient losses. This study examined the effect of applying crop residues to the soil surface on the basic cation nutrient [calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na)] losses by runoff from a tilled soil with relatively low organic-matter content. Runoff and sediment yield were measured on 1-m2 plots using a rainfall simulator with constant 65 mm h?1 intensity. Four successive rainfall applications were performed, the first three at 25 mm each and the last at 65 mm. Added corn straw varied between 0 and 4 t ha?1 in the five treatments studied. Total and dissolved concentrations of the elements studied showed a tendency to decrease due to the effect of corn straw on soil losses. After 140 mm cumulative rainfall, total nutrient losses were as follows: Ca from 12.32 to 28.94 mg L?1, Mg from 20.81 to 148.90 mg L?1, K from 14.20 to 35.17 mg L?1, and Na from 14.99 to 23.41 mg L?1. The relative contribution of the dissolved fraction to the total nutrient content loss was highly variable, being up to 90% for Na. The results confirm that corn residues applied to a degraded soil, with low structural stability, prevent cation nutrient losses.  相似文献   

14.
Improved legume tree fallows have great potential to increase soil organic carbon (SOC), aggregate stability and soil infiltration rates during the fallowing phase. However, persistence of the residual effects of improved fallowing on SOC, aggregate stability and infiltration rates, under different tillage systems in Zimbabwe is not well documented. The relationships between SOC, aggregate stability and infiltration in fallow-maize rotation systems are also not well documented. We therefore evaluated effects of tillage on SOC, aggregate stability and infiltration rates of a kaolinitic sandy soil during the cropping phase of an improved fallow-maize rotation system. Plots that were under legume tree fallows (Sesbania sesban; Acacia angustissima), natural fallow (NF) and under continuous maize during the previous 2 years were divided into conventional tillage (CT) and no-till (NT) subplots soon after fallow termination, and maize was cropped in all plots during the following two seasons. Aggregate stability was investigated using water stable macroaggregation index (Ima), water dispersible clay (WDC) and using the mean weight diameter (MWD) after different wetting procedures. Infiltration rates were determined using simulated rainfall at intensity of 35 mm h−1 on 1 m2 plots. Soil organic carbon was significantly higher (P < 0.05) under fallows than continuous maize. For the 0–5 cm depth SOC was 11.0, 10.0, 9.4 and 6.6 g kg−1 for A. angustissima, S. sesban, NF and continuous maize, respectively, at fallow termination. After 2 years of cropping SOC was 8.0, 7.0, 6.1 and 5.9 g kg−1 under CT and 9.1, 9.0, 8.0 and 6.0 g kg−1 under NT for A. angustissima, S. sesban, NF and continuous maize, respectively. Aggregate stability was significantly greater (P < 0.05) under fallows than under continuous maize and also higher under NT than under CT. The macroaggregation index (Ima) for the 0–5 cm depth was 466, 416, 515 and 301 for A. angustissima, S. sesban, NF and continuous maize, respectively at fallow termination, decreasing to 385, 274, 286 and 255 under CT and 438, 300, 325 and 270 under NT, for A. angustissima, S. sesban, NF and continuous maize, respectively, after 2 years of cropping. Percent WDC was also significantly lower (P < 0.05) in fallows than in continuous maize, and for the 0–5 cm it was 11, 10, 8 and 17 for A. angustissima, S. sesban, NF and continuous maize, respectively at fallow termination. After 2 years of cropping WDC (%) was 12, 14, 15 and 17 under CT and 10, 12, 12 and 16 under NT for A. angustissima, S. sesban, NF and continuous maize, respectively. MWD also showed significantly higher (P < 0.05) aggregate stability in fallows than in continuous maize. Water infiltration rates were significantly greater under fallows than continuous maize but these declined significantly during the cropping phase in plots that had been fallowed. In October 2000, infiltration rates in the A. angustissima and NF plots were above 35 mm h−1 as no runoff was observed. Steady-state infiltration rates were 24 mm h−1 in S. sesban and 5 mm h−1 for continuous maize after 30 min of rainfall simulations. After 2 years of cropping infiltration rates remained above 35 mm h−1 in A. angustissima plots, but declined to 18 and 8 mm h−1 for NF, CT and NT respectively and 12 mm h−1 for S. sesban, CT and NT. It is concluded that legume tree fallows improved SOC, aggregate stability and infiltration rates, but these benefits accrued during fallowing decreased significantly after 2 years of cropping following the termination of fallows. The decrease in SOC and aggregate stability was higher under CT than NT. Coppicing fallows of A. angustissima were the best long-term fallow species when integrated with NT as improved soil physical properties were maintained beyond 2 years of post-fallow cropping.  相似文献   

15.
Minimizing slurry phosphorus (P) losses in runoff requires careful management in the context of both soil P surpluses and changing patterns in rainfall. Increasing the time interval between slurry application and the first rainstorm event is known to reduce P loss in runoff although the risk period for elevated P concentrations in runoff can extend for weeks. This study investigated the impact of increasing the time interval between slurry application and first rainstorm event on P concentrations in runoff. Simulated rainfall (40 mm h−1) was applied at 2, 4, 10, 18, 30 and 49 days after dairy slurry was surface-applied to a grassland sward in Ireland. Increasing time to runoff resulted in a decrease in dissolved reactive P concentrations from 5.0 to 1.0 mg P L−1 and a P signal in runoff for 18 days. Beyond 18 days, elevated P concentrations were observed in runoff collected from natural rainfall that preceded the day 49 rainstorm event. A published surface phosphorus and runoff model (SurPhos) was used to understand the slurry P dynamics controlling P interactions with runoff. Dissolved reactive P in runoff was predicted with accuracy by SurPhos, R2 = .89. The SurPhos model implied that slurry P mineralization occurred during the experimental period that resulted in a small spike in P concentrations beyond the defined risk period. This study shows that the experimental data have the potential to be extrapolated to different weather scenarios using SurPhos and could test when and where slurry P could be most safely spread.  相似文献   

16.
Li  Jianming  Wang  Wenlong  Guo  Mingming  Kang  Hongliang  Wang  Zhigang  Huang  Jinquan  Sun  Baoyang  Wang  Ke  Zhang  Guanhua  Bai  Yun 《Journal of Soils and Sediments》2020,20(11):3896-3908
Purpose

Large spoil heaps formed during construction projects have caused serious soil erosion and threatened ecological security. The recent researches on soil erosion of spoil heaps are based on one or several soil types, which can only represent the soil texture category within the limited area, but cannot be used in other larger scale areas. Soil texture and gravel are the main factors affecting infiltration and erosion processes of spoil heaps.

Materials and methods

The runoff plot dimensions were 5.0 m?×?1.0 m?×?0.5 m (length × width × depth). A series of rainfall experiments with a constant rainfall intensity of 1.0 mm min?1 and a slope gradient of 25° were conducted to investigate the effects of soil texture (sandy, loam, and clay) and gravel mass content (GC, 0%, 10%, 20%, and 30%) on the infiltration and erosion processes. The gravels are divided into 3 classes according to particle size 2–14 mm (small), 14–25 mm (medium), 25–50 mm (large), and the mass ratios were 30%, 50%, and 20%. The duration of each rainfall event was 45 min after runoff out of the plot.

Results and discussion

Results showed that there was a critical GC (10%) improving or controlling infiltration and soil loss. Infiltration rate of sandy spoil heap (SSH) decreased within 45 min, but it decreased first and then stabilized for loam spoil heap (LSH) and clay spoil heap (CSH). Soil loss rate (SLR) of SSH stabilized first and then increased, while it decreased and then stabilized for LSH and CSH. SLR at early stage (0–18 min) was 0.08–0.23 times than it was at later stage (18–45 min) for SSH, but it was 2.06–5.06 times and 1.46–1.95 times for LSH and CSH, respectively. The soil texture had a more significant effect on SLR (P?< 0.05) than GC did. The effects of gravel on SLRs were dependent on soil texture.

Conclusions

The greater the GC was, the lower the SLR was for the spoil heaps. Special attention should be paid to the later stage during rainfall events for SSHs and the early stage for LSHs and CSHs when considering erosion protection measures.

  相似文献   

17.
Semiarid karst landscapes represent an important ecosystem surrounding the Mediterranean Basin for which little is known on runoff generation. Knowledge of the sources and patterns of variation in infiltration–runoff processes and their controls is important for understanding and modelling the hydrological functions of such ecosystems. The objectives of this paper are to determine the infiltration rates and their controls in a representative mountain karst area (Sierra de Gádor, SE Spain) at micro-plots and to investigate the integrated response of rainfall on a typical hillslope. Rainfall simulations in micro-plots and natural rainfall-runoff monitoring on a hillslope were carried out complementarily. We investigated the role of soil surface components (vegetation, rock outcrop, fracture, and soil crust), topographic position, antecedent soil moisture, and rainfall characteristics in regulating infiltration–runoff processes. Results of rainfall simulation revealed the importance of vegetation cover and the presence of rock fractures in promoting the infiltration in the limestone karst landscape, while bare patches and rock outcrops acted as sources for runoff. All plots with > 50% vegetation cover had no runoff with up to 55 mm h− 1 of simulated rain. In contrast, nearly all bare plots had runoff under the same simulated rain, with runoff coefficients ranging from 3.1 to 20.6% on dry soil surface conditions, and from 2.0 to 65.4% on wet soil surfaces. Runoff coefficients amounted to 59.0–79.5% for rock outcrops without cracks, but were drastically reduced by the presence of cracks. The surfaces with rock fragments resting on the soil (generally located in the middle of the slopes) prevented more effectively the runoff generation than those surfaces where rock fragments were embedded in the top soil. Antecedent soil moisture had significant impact on runoff generation, with wet soil having doubled runoff coefficient, shortened time to runoff, and increased runoff rate compared to the same but dry soil. Linear regressions indicated that the main controls for constant infiltration rate were the cover percentages of vegetation and litter, plus rainfall intensity; while the major controls for runoff coefficient were the bare soil and vegetation coverage, plus rainfall intensity. High infiltration rates measured at the micro-plots agreed with low intra-event runoff coefficients (mostly below 1%) observed under natural rainfalls at the hillslope. Runoff depth and coefficient at the hillslope was significantly correlated with rainfall depth, maximum hourly rainfall intensity and antecedent precipitation over 20 days (AP20). During the 1.5-year monitoring period from Sep-2003 to Mar-2005, the overall infiltration was 41% of the total rainfall amount and the maximum infiltration rate was almost 94% of the largest single rainfall event. The results from this study contribute to improved understanding of the magnitude and controls of the surface runoff in semiarid karst mountain areas.  相似文献   

18.
This study was carried out to observe the dynamics of crust formation on the soil surface under field conditions and analyse the effects of seedbed structure and water content on soil surface crusting. Seedbed sensitivity to crusting was also estimated in the laboratory by stability tests on aggregates. We observed 57 plots during the sowings of spring and autumn crops in fields in Northern France (Estrees-Mons, 50°N latitude, 3°E longitude). The soil is an Orthic Luvisol according to the FAO classification (0.17–0.25 g g−1 clay and 0.02 g g−1 organic matter on average). Visual assessments in situ were performed and photographs taken of crust stages on delimited areas, each 5 mm of cumulated rainfall since sowing. In 2004–2005, the seedbeds were characterised by their distribution of aggregate sizes and tests of aggregate stabilities of surface samples kept with their water content at sowing. A penetrometer was used to measure crust resistance and estimate its thickness. These data were analysed to detect the cumulative rainfall values needed for the initiation and development of the successive stages of crusts. A fully developed structural crust (stage F1) required 13, 22, 27 mm cumulated rainfall respectively for seedbeds with proportions of clods over 2 cm ranging from 0 to 0.15 (fine seedbed), 0.15 to 0.30 (medium seedbed), >0.30 g g−1 (coarse seedbed). Aggregate stability measured on samples kept at sowing water content was low for soil with low water content (<0.17 g g−1) but increased sharply for water contents over 0.17 g g−1. Stage F1 was reached more rapidly (only 11 mm versus 19 mm cumulated rainfall) only for fine seedbeds with less than 0.15 g g−1 of clods over 2 cm and with a low water content at sowing, The stage of 50% of soil surface covered with sedimentary crusts was reached for 85 mm for fine seedbed versus 120 mm for medium seedbed. The mean penetrometer resistance of dry crusts was 0.55 ± 0.43 MPa for stage F1 and 3.54 ± 0.83 MPa for a sedimentary stage; mean penetrometer resistance increased continuously with cumulated rainfall and was much lower for wet crusts. These quantitative data gathered under field conditions constitute the first step towards the prediction of soil surface crusting. The cumulative rainfalls were used in order to estimate the risk of occurrence of structural and sedimentary crusts forming during crop emergence with several types of seedbeds.  相似文献   

19.
Runoff may cause losses of micronutrients from soils. This can result in environmental problems such as contaminant transfers to water or a decrease in soil fertility. Appropriate soil management may reduce these micronutrient losses. This study examined the effect of applying crop residues to the soil surface on iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) losses by runoff. Runoff and sediment yield were measured on 1-m2 plots using a rainfall simulator with constant 65 mm h?1 intensity. Eight successive rainfall applications were performed at 65 mm each. Corn (Zea mays L.) straw was applied to plots at rates ranging from 0 to 8 t ha?1. Both total and dissolved concentrations of the micronutrients studied were decreased by corn straw applications. After 520 mm cumulative rainfall, total soil losses ranged from 150 to 15354 kg ha?1 depending on the amount of corn straw applied. Total micronutrient concentrations in runoff were as follows: Fe from 14.98 to 611.12 mg L?1, Mn from 0.03 to 0.61 mg L?1, Cu from 0.10 to 1.43 mg L?1, and Zn from 0.21 to 5.45 mg L?1. The relative contribution of the dissolved fraction to the total micronutrient content loss was low, but varied depending on the nutrient, being less than 1 percent for Fe and Mn and almost 10 percent for Zn. Total and dissolved concentrations in runoff of the studied elements decreased exponentially as the rate of applied corn straw increased. In conclusion, the addition of corn straw to soil reduced micronutrient losses.  相似文献   

20.
The Brazilian Cerrado has been converted to farmland, and there is little evidence that this expansion will decrease, mainly because agriculture is the country’s main economic sector. However, the impacts of intense modification of land use and land cover on surface runoff and soil erosion are still poorly understood in this region. Here, we assessed surface runoff and soil loss in a woodland Cerrado area under a former pasture area, which was abandoned and has undergone a natural regeneration process for 7 years (RC). Its results were compared with that found in an undisturbed area of woodland Cerrado (CE), 40-month-old eucalyptus (3.0 × 1.8 m) (EU), and pasture under rotational grazing (PA). The study was conducted on Red Acrisol located in the Brazilian Cerrado. We performed rainfall simulations on a plot of 0.7 m2 and using three constant rainfall intensities of 60, 90, and 120 mm h−1 for 1 h. For each rainfall intensity, we carried out four repetitions using different plots in each treatment, i.e. 12 plots per treatment studied and 48 plots in total. We noted that the soil physical properties were improved in RC and, consequently, water infiltration and soil erosion control; RC presented surface runoff and soil loss different from EU and PA (α = 0.05). The macroporosity and soil bulk density affected surface runoff in RC and PA because the RC was used as pasture and is currently regenerating back to the cerrado vegetation. As the rainfall intensity increased, EU became more similar to PA, which showed the highest surface runoff and soil loss. Our findings indicate that natural regeneration processes (pasture to the cerrado vegetation) tend to improve the soil ecosystem services, improving infiltration and reducing surface runoff and soil erosion.  相似文献   

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