Assessment of soil erosion rates in a Mediterranean cultivated and uncultivated soils using fallout 137Cs

Effects of Wind-Water Erosion and Topographic Factor on Soil Properties in the Loess Hilly Region of China

Wind and water erosion processes can lead to soil degradation. Topographic factors also affect the variation of soil properties. The effect of topographic factors on soil properties in regions where wind and water erosion simultaneously occur remains complicated. To address this effect, we conducted this study to determine the relationships between the changes in wind-water erosion and soil properties in different topographic contexts. We collected soil samples from conical landforms with different slope characteristics and positions in the wind-water erosion crisscross region of China. We examined the soil ¹³⁷Cs inventory, soil organic carbon (SOC), total nitrogen (TN), soil particles, soil water content (SWC), and biomass. ¹³⁷Cs was applied to estimate soil erosion. The results show that the soil erosion rate followed the order of northwest slope > southwest slope > northeast slope > southeast slope. The soil erosion rate on the northwest slope was about 12.06-58.47% higher than on the other. Along the slopes, the soil erosion rate decreased from the upper to the lower regions, and was 65.65% higher at the upper slope than at the lower one. The change in soil erosion rate was closely related to soil properties. The contents of SOC, TN, clay, silt, SWC, and biomass on the northern slopes (northwest and northeast slopes) were lower than those on the southern slopes (southeast and southwest slopes), and they were lower at the upper slope than at the lower one. Redundancy analysis showed that the variation in soil properties was primarily affected by the slope aspect, and less affected by soil erosion, accounting for 56.1% and 30.9%, respectively. The results demonstrate that wind-water erosion accelerates the impact of topographic factors on soil properties under slope conditions. Our research improves our understanding of the mechanisms of soil degradation in gully regions where wind and water erosion simultaneously occur.

Behaviour of 137Cs and 210Pb inventory at three candidate reference sites for erosion study in the upstream Citarum watershed area, West Java, Indonesia

The fallout radionuclide (FRN) analysis needs a reference site (RS) inventory to determine erosion and sedimentation in the study area. The investigated area is in the upstream Citarum watershed, West Java, Indonesia. Twenty-seven corings and 22 scrap samples have been prepared well and measured using HPGe gamma spectroscopy. The data below the minimum detectable activity (MDA) was found for ¹³⁷Cs in RS6 cor 4 and 7 (<0.16 ± 0.08 Bq kg^-1). MDA quantification implies that the inventory below MDA eroded greater than its maximum value (76.02 tons ha^-1 a^-1). The comparison ¹³⁷Cs inventory in this study is lower than the three estimation models; however, the inventory of Mt. Papandayan is closer to the model. This study found the depth percentage of 20-30 cm using the proportion of 0-20 cm/0-30 cm ratio and predicted the portion of the existence of ¹³⁷Cs and ²¹⁰Pb_ex in the 20-30 cm in the bulk sample. The highest H₀ (142.04 kg m^-2), the relaxation length λ, and proportion of 20% of ¹³⁷Cs in 20-30 cm depth imply that ¹³⁷Cs inventory activity is possibly deeper than 30 cm. This study recommends that Mt. Papandayan could be the alternative RS for the upstream Citarum watershed.

Soil water erosion assessment in Morocco through modeling and fingerprinting applications: A review

During the last century, a great deal of effort has been directed toward determining soil erosion rates using various methods under a wide range of climatic conditions, soil types, land uses, topography, and among others. Therefore, to better understand soil erosion studies in Morocco, a country with diverse physiography and climatic variations we undertook an analysis of national data of several soil erosion modeling and fingerprinting. The approach used for this research is a review of scientific articles, conference papers and thesis on soil erosion, focusing more on categorization of the different soil erosion models and other methods applied. The results reveal very interesting information as follows: (i) the distribution and frequency level of modeling and fingerprinting applications; the focus was on the north of the country: (Rif 32.89%, High Atlas 32.89%, Occidental Meseta 18.43% and Middle Atlas 10.53%), (ii) The (R) USLE models remain the most widely used models (51,32%) in Morocco, (iii) The support practice factor was severely lacking across the country, (iv) the highest erosion rate is concentrated in the Atlas and Rif mountains; and (v) a positive relationship between erosion rate and geological features, slope, climate, land use and cover, plus other environmental characteristics, as well as measurement and modeling conditions, and a negative relationship with the study areas size and scale. Even though the overall results show a high degree of variability, which cannot be explained by this combination of factors, but is at a minimum partly related to the experimental conditions. This overview research and database are designed to assist in the future assessment of soil erosion and to help define priorities for soil erosion research by providing a state of art for future focused and comprehensive analyses to address this issue of soil erosion in Morocco.

Estimation of Soil Erosion and Evaluation of Soil and Water Conservation Benefit in Terraces under Extreme Precipitation

In recent years, soil erosion caused by water erosion has gradually increased due to the increase of extreme precipitation. In order to reduce soil erosion caused by extreme precipitation, it is necessary to monitor soil erosion and found out the factors that affect soil erosion under extreme precipitation. The objective of this study was to assess the amount of soil erosion, the damage degree of soil and water conservation measures and benefit evaluation under extreme precipitation in Henan Province. The results indicated that the ridges of terraces in two small watersheds had been damaged to varying degrees. Terraces, as one of soil and water conservation measures, can better preserve soil and water erosion under extreme precipitation. The amount of soil preserved in two small watersheds were 744.50t and 1121.01t. The amount of soil loss in two small watersheds were reduced by 67.67% and 78.63% when terraces existed. The soil conservation amount of vegetation restoration measures in two small watersheds were 2960.23t and 3320.36t. The amount of soil loss in two small watersheds were reduced by 89.27% and 90.98%, when vegetation restoration measures exist. Compared with soil and water conservation engineering measures, vegetation restoration measures can better reduce soil erosion caused by water erosion under extreme precipitation. In addition to the amount of rainfall, the soil and water conservation benefits of terraces were also affected by the width of the terrace, the slope of the terrace, and whether there were vegetation restoration measures in the terrace.

Meteoric 10Be, 137Cs and 239+240Pu as Tracers of Long- and Medium-Term Soil Erosion—A Review

Isotopes of meteoric 10Be, 137Cs, 239+240Pu have been proposed as a soil redistribution tracer and applied worldwide as an alternative method to classical field-related techniques (e.g., sediment traps). Meteoric 10Be provides information about long-term soil redistribution rates (millennia), while 137Cs and 239+240Pu give medium-term rates (decades). A significant progress in developing new models and approaches for the calculation of erosion rates has been made; thus, we provide a global review (n = 59) of research articles to present these three isotopes (meteoric 10Be, 239+240Pu and 137Cs) as soil erosion markers in different environments and under different land-use types. Understanding the dynamics and behaviours of isotopes in the soil environment is crucial to determine their usefulness as soil erosion tracers; thus, we discuss the chemical–physical behaviour of meteoric 10Be, 137Cs and 239+240Pu in soils. The application of these isotopes sometimes has strong limitations, and we give suggestions on how to overcome them or how to adapt them to a given situation. This review also shows where these isotopic methods can potentially be applied in the future. A lack in knowledge about soil redistribution rates exists particularly in loess-dominated areas where the tillage system has changed or in areas with strong wind erosion.

Soil nutrient variability mediates the effects of erosion on soil microbial communities: results from a modified topsoil removal method in an agricultural field in Yunnan plateau, China

Soil erosion can affect the nature and distribution of soil carbon and nutrients, directly and indirectly influencing microbially facilitated processes of mineralization, ammoniation, and nitrification, thus affecting soil nutrients cycling. However, little is known about how soil erosion affects soil microorganisms. Since 2012, we conducted a modified soil erosion simulation experiment of topsoil removal method in an agricultural field to simulate erosion depths of 5, 10, 20, 30, and 40 cm versus a control (0 cm). The results showed that Proteobacteria, Bacteroidetes, Acidobacteria, Chloroflexi, Actinobacteria, and Firmicutes were the dominant soil microbial (here: Bacteria and Archaea) phyla, and Acidothermus, Candidatus Solibacter, Acidibacter, Bryobacter, and Actinospica were the dominant genera in all samples. The relative abundance of Proteobacteria, Acidobacteria, Actinobacteria, Planctomycetes, Thaumarchaeota, Acidothermus, Candidatus Solibacter, Acidibacter, Bryobacter, Actinospica, and Rhodanobacter decreased with the increase of erosion depths, while Chloroflexi and Firmicutes increased with the increase of erosion depths. Soil microbial community structure was altered significantly at 30- and 40-cm soil erosion depth in comparison to control. Soil nutrient variability caused by soil erosion had a greater impact on soil microbial community composition than that of soil mechanical composition. Soil erosion indirectly affected microbial community composition through negative effects on soil available potassium, total phosphorus, total nitrogen, and sand content. We thus highlight the importance of soil nutrients monitoring in different soil erosion levels to make the proper ecological restoration strategies to improve soil environment which soil microorganisms depend on.

Investigation of the effect of anthropogenic land use on the Pănăzii Lake (Romania) catchment area using Cs-137 and Pb-210 radionuclides

The problem of soil degradation has accentuated over recent decades. Aspects related to soil erosion and its relation to changes in land use as well as anthropogenic influence constitute a topic of great interest. The current study is focused on a soil erosion assessment in relation to land use activities in the Pănăzii Lake catchment area. Fallout radionuclides were used to provide information on soil erosion as well as redistribution rates and patterns. Variations in the sedimentation rate of the lake were also investigated as these reflect periods in which massive erosion events occurred in the lake catchment area. The novelty of this study is the construction of a timescale with regard to the soil erosion events to better understand the relationship between soil erosion and land use activities. In this study, 10 soil profiles and one sediment core from the lake were taken. Soil parameters were determined for each sample. The activities of 210Pb, 137Cs and 226Ra were measured by gamma spectroscopy. For low 210Pb activities, measurements via 210Po using an alpha spectrometer were performed. Soil erosion rates were determined by the 137Cs method and the sedimentation rate calculated by the Constant Rate of Supply (CRS) model. A soil erosion rate of 13.5 t·ha-1·yr-1 was obtained. Three distinct periods could be observed in the evolution of the sedimentation rate. For the first period, between 1880 and 1958, the average deposition rate was 9.2 tons/year, followed by a high deposition period (1960-1991) of 29.6 tons/year and a third period, consisting of the last 30 years, during which the sedimentation rate was 15.7 tons/year. These sedimentation rates fluctuated depending on the main land use activity, which can also be seen in the soil erosion rates that had almost doubled by the time agricultural activities were performed in the area.

Combination of 137Cs and 210Pb Radioactive Atmospheric Fallouts to Estimate Soil Erosion for the Same Time Scale

Naturally occurring ²¹⁰Pb and artificial ¹³⁷Cs fallouts are widely used as radioactive tracers for the determination of water-induced soil erosion for different time scales equal to 50 and 100 years, respectively. There exist several calibration models useful to convert the variation of the inventory of these radiotracers in cultivated soil compared to its value on non-disturbed soil to a soil erosion rate. The most comprehensive calibration models are based on a mass balance approach. In the present work, a new calibration model is proposed. It consists on the generalization of the mass balance approach to a cultivated soil subject to two successive and continuous periods of cultivation. The proposed model combines ²¹⁰Pb and ¹³⁷Cs fallouts for the same time scale by relaxing the constraint on ²¹⁰Pb fallout from being used for 100 years’ time scale. The model was applied successfully to hypothetical cases and can be used to measure soil erosion rates for practical cases. It is important to note that the proposed model has two main advantages. First, the complementarity between ²¹⁰Pb and ¹³⁷Cs fallouts is for the same time scale and not for different time scales, as usually considered and believed in this field. Second, ²¹⁰Pb fallout is used for time scales less than 100 years. This makes the model useful to estimate soil erosion rates for two successive periods of cultivation. To the best knowledge of the authors, the combination of ²¹⁰Pb and ¹³⁷Cs fallouts for the determination of soil erosion rate variation due to change in cultivation practices for the same time scale has never been developed or applied in the past.

Tillage Versus No-Tillage. Soil Properties and Hydrology in an Organic Persimmon Farm in Eastern Iberian Peninsula

There is an urgent need to implement environmentally friendly agriculture management practices to achieve the Sustainable Goals for Development (SDGs) of the United Nations by 2030. Mediterranean agriculture is characterized by intense and millennia-old tillage management and as a consequence degraded soil. No-Tillage has been widely examined as a solution for soil degradation but No-Tillage relies more on the application of herbicides that reduce plant cover, which in turn enhances soil erosion. However, No-Tillage with weed cover should be researched to promote organic farming and sustainable agriculture. Therefore, we compare Tillage against No-Tillage using weed cover as an alternative strategy to reduce soil losses in persimmon plantations, both of them under organic farming management. To achieve these goals, two plots were established at “La Canyadeta” experimental station on 25-years old Persimmon plantations, which are managed with Tillage and No-Tillage for 3 years. A survey of the soil cover, soil properties, runoff generation and initial soil losses using rainfall simulation experiments at 55 mm h−1 in 0.25 m2 plot was carried out. Soils under Tillage are bare (96.7%) in comparison to the No-Tillage (16.17% bare soil), with similar organic matter (1.71 vs. 1.88%) and with lower bulk densities (1.23 vs. 1.37 g cm3). Tillage induces faster ponding (60 vs. 92 s), runoff (90 vs. 320 s) and runoff outlet (200 vs. 70 s). The runoff discharge was 5.57 times higher in the Tillage plots, 8.64 for sediment concentration and 48.4 for soil losses. We conclude that No-tillage shifted the fate of the tilled field after 3 years with the use of weeds as a soil cover conservation strategy. This immediate effect of No-Tillage under organic farming conditions is very promising to achieve the SDGs.