Agricultural Soil Erosion Research Articles

Runoff Estimation in Kajurli Watershed Using SCS-CN and GIS Techniques

The study focuses on estimating surface runoff using the Soil Conservation Service Curve Number (SCS-CN) method, combined with Remote Sensing (RS) and Geographic Information System (GIS) techniques, for the Kajurli Watershed in Ratnagiri District, Maharashtra. Surface runoff is a key factor influencing agricultural productivity, soil erosion, and water management at the watershed level. The SCS-CN method, a widely used tool for runoff estimation, utilizes rainfall, land use, and soil type data. By integrating RS and GIS, the study achieves a more accurate assessment of land use and soil characteristics, which are critical inputs for runoff calculations. The Kajurli Watershed falls under hydrological soil group B, known for moderate runoff potential. The study uses 33 years of historical rainfall data (1990-2022) to compute annual runoff using the SCS-CN method. Key parameters such as Curve Numbers (CN) are derived based on land use, hydrological soil groups, and antecedent moisture conditions (AMC). The average annual rainfall in the watershed is found to be 3392.8 mm, with 39.69% of this rainfall contributing to surface runoff. The integration of RS and GIS simplifies spatial analysis, enabling accurate and efficient runoff estimation. The study highlights the sensitivity of the SCS-CN method to CN values, emphasizing the importance of precise land use and soil data for reliable hydrological modelling. These findings offer crucial insights for water resource management, flood control, and agricultural planning in the region.

Assessing monthly dynamics of agricultural soil erosion risk in Poland

Soil erosion in agricultural landscapes poses a significant threat to soil health and productivity. This study investigates the dynamics of soil erosion across agricultural lands in Poland at monthly scale using the Revised Universal Soil Loss Equation (RUSLE) model. The study utilizes the Global Rainfall Erosivity Dataset (GLOREDA), which provides the most up-to-date and highest resolution rainfall erosivity (R) values, derived from 10-min resolution rainfall records. Additionally, satellite imagery spanning 2003 to 2023 was leveraged to estimate the cover-management (C) factor, capturing the spatial and temporal dynamics of vegetation cover and agricultural practices. Results reveal significant spatio-temporal variations in soil erosion rates, with peak erosion occurring during the summer months following crop harvesting, despite not aligning precisely with peak rainfall erosivity. The lowest erosion rates are observed during the winter seasons, attributed to minimal rainfall erosivity. The findings highlight the critical role of agricultural practices, particularly the timing of crop harvesting and temporary exposure of bare soil, in driving soil erosion dynamics in Poland's agricultural landscapes. Specifically, the average annual soil loss for agricultural areas in Poland was determined to be 0.27 t ha−1 yr−1, with peak monthly soil erosion rates reaching up to 0.08 t ha−1 yr−1 in August. Total monthly soil loss from agricultural lands in Poland was estimated to be approximately 4.87 Mt. annually, with 68 % of the total annual soil loss occurring during the summer months. This study contributes valuable insights into understanding and managing soil erosion risks in agricultural systems, aiding in the development of targeted soil conservation strategies and sustainable land management practices.

Late Holocene rapid paleoenvironmental changes and anthropogenic impacts in central Yunnan, southwest China

Understanding long-term anthropogenic impact on the Earth's surface system is crucial for establishing reference conditions and potentially allowing future trajectories to be more rigorous and tightly constrained. In this study, the evolution of catchment erosion, chemical weathering and bottom-water hypoxia during the late Holocene are investigated using multi-proxy records from an accurately-dated sediment core from Lake Qilu in central Yunnan, southwest China. Through the comparison of our results with other paleoenvironmental records from the study region, we are able to see that the increase in anthropogenic impact on the catchment of Lake Qilu began in 780 CE, which is associated with the large scale expansion of agriculture in China. In the early stages of vegetation disturbance and agricultural land use, soil erosion and chemical weathering within in the catchment was significantly intensified, while the lake gradually changed to a state of anoxia until the period of accelerating eutrophication in 1945 CE. However, the extremely high rate of soil erosion and weak chemical weathering suggest the beginning of a new phase in terms of anthropogenic impact on the landscape. Furthermore, the late Holocene intensification of chemical weathering in monsoonal China can also be linked to increased anthropogenic activities rather than spatial differences in hydroclimate changes. This study highlights the fact that humans have been shaping the Earth's surface for millennia, which means that it is essential to place present environmental concerns into a long-term context.

Soil erosion is a major drive for nano & micro-plastics to enter riverine systems from cultivated land

Nano and micro-plastics (NMPs, particles diameter <5 mm), as emerging contaminants, have become a major concern in the aquatic environment because of their adverse consequences to aquatic life and potentially human health. Implementing mitigation strategies requires quantifying NMPs mass emissions and understanding their sources and transport pathways from land to riverine systems. Herein, to access NMPs mass input from agricultural soil to riverine system via water-driven soil erosion, we have collected soil samples from 120 cultivated land in nine drainage basins across China in 2021 and quantified the residues of six common types of plastic, including polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polypropylene (PP), polyethylene (PE), polycarbonate (PC), and polystyrene (PS). NMPs (Σ6plastics) were detected in all samples at concentrations between 3.6 and 816.6 μg/g dry weight (median, 63.3 μg/g) by thermal desorption/pyrolysis-gas chromatography-mass spectrometry. Then, based on the Revised Universal Soil Loss Equation model, we estimated that about 22,700 tonnes of NMPs may enter the Chinese riverine system in 2020 due to agricultural water-driven soil erosion, which occurs primarily from May to September. Our result suggested that over 90% of the riverine NMPs related to agricultural soil erosion in China are attributed to 36.5% of the country's total cultivated land, mainly distributed in the Yangtze River Basin, Southwest Basin, and Pearl River Basin. The migration of NMPs due to water-driven soil erosion cannot be ignored, and erosion management strategies may contribute to alleviating plastic pollution issues in aquatic systems.

Deep optimization of water quality index and positive matrix factorization models for water quality evaluation and pollution source apportionment using a random forest model

Effective evaluation of water quality and accurate quantification of pollution sources are essential for the sustainable use of water resources. Although water quality index (WQI) and positive matrix factorization (PMF) models have been proven to be applicable for surface water quality assessments and pollution source apportionments, these models still have potential for further development in today's data-driven, rapidly evolving technological era. This study coupled a machine learning technique, the random forest model, with WQI and PMF models to enhance their ability to analyze water pollution issues. Monitoring data of 12 water quality indicators from six sites along the Minjiang River from 2015 to 2020 were used to build a WQI model for determining the spatiotemporal water quality characteristics. Then, coupled with the random forest model, the importance of 12 indicators relative to the WQI was assessed. The total phosphorus (TP), total nitrogen (TN), chemical oxygen demand (CODCr), dissolved oxygen (DO), and five-day biochemical oxygen demand (BOD5) were identified as the top five significant parameters influencing water quality in the region. The improved WQI model constructed based on key parameters enabled high-precision (R2 = 0.9696) water quality prediction. Furthermore, the feature importance of the indicators was used as weights to adjust the results of the PMF model, allowing for a more reasonable pollutant source apportionment and revealing potential driving factors of variations in water quality. The final contributions of pollution sources in descending order were agricultural activities (30.26%), domestic sewage (29.07%), industrial wastewater (26.25%), seasonal factors (6.45%), soil erosion (6.19%), and unidentified sources (1.78%). This study provides a new perspective for a comprehensive understanding of the water pollution characteristics of rivers, and offers valuable references for the development of targeted strategies for water quality improvement.

Determination of soil organic carbon content of agricultural soils for proper soil management in Matazu and Musawa, Katsina State, Nigeria

Soil organic carbon is a significant parameter for estimating the global carbon cycle, which makes great sense in soil management and future climate scenario prediction. This work uses 30 heterogeneous soil samples from agricultural and non-agricultural farmlands and soil erosion areas in Matazu and Musawa LGAs to determine soil organic carbon content at the field level in Matazu and Musawa Local Government Areas, Katsina State, Nigeria. Soil samples were meticulously collected from the 0-10cm depth using a hand auger. These samples were obtained from three distinct clusters: agricultural and non-agricultural farmlands and soil erosion areas. The selection of sample locations considered the varied soil types, historical land use, and management practices. Ten soil samples were randomly gathered within each cluster, ensuring a representative and diverse set of samples for analysis. The Warlkey and Black and Hydrometer methods were used to determine the soils' organic carbon contents and particle size distribution, respectively. The data obtained were analyzed using SPSS 23 software. Two-sample t-tests and analysis of variance (ANOVA) were carried out. The soil organic carbon contents of the studied area were 0.29 ± 0.16 g/kg (0.16 – 0.34 g/kg) and 0.28 ± 0.14 g/kg (0.14 - 0.36 g/kg) for Matazu and Musawa, respectively. The study concludes that the organic carbon content helps improve sustainable agricultural productivity due to proper and efficient land use management practices.

Soil Erosion Research Studies in the Age of Changing Climate

HIGHLIGHTSSoil erosion research has evolved over a century to address critical societal needs.This collection features 12 articles from the 2023 ASABE Soil Erosion Research Symposium.Links to Symposium proceedings and presentations are provided.Soil erosion modeling, methods, and measurement advances are highlighted from the collection.Abstract. This article introduces a collection of 12 articles featured from a decennial international American Society of Agricultural and Biological Engineers (ASABE) soil erosion research symposium in Aguadilla, Puerto Rico, in January 2023. Over 130 engineers and scientists met to discuss current soil erosion issues, research techniques, and erosion prediction technologies. In addition to the meeting presentations and proceedings (116 abstracts or papers available online), twelve articles were published in a special collection in the ASABE journals. Information on the ASABE Soil Erosion Research Under a Changing Climate international symposium and details on the special collection of articles are provided in this paper. Articles are aggregated into soil erosion-related topical areas of modeling, methods, and measurement, and article highlights are presented. A common theme was the need for standardized measurements and methods to compare processes and impacts across geographic and climate regions and to assess model performance and prediction for extension of methods to other watersheds. Keywords: Erosion control, Hydrology, Sediment, Sedimentation, Soil conservation, Soil erosion modeling, Soil pollution, Water quality.

Expert elicitations of smallholder agroforestry practices in Seychelles: A SWOT-AHP analysis

Agroforestry can leverage the co-benefits of climate change adaptation and mitigation while conserving biodiversity and restoring degraded and deforested lands. The preference of relevant stakeholders regarding agroforestry practices enhances sustainable land management through strategic decision-making in Seychelles and other island states. A suitable approach for assessing stakeholders’ preferences of agroforestry is the implementation of the strengths, weaknesses, opportunities, and threats (SWOT) approach in combination with the analytic hierarchy process (AHP) method. The entry point of this study is an extensive literature review process, during which 28 SWOT factors were identified. These SWOT factors were deliberated on during a half-day workshop with agricultural experts who agreed on 20 SWOT factors that reflect the local realities of the Seychelles through a consensus approach. Using the SWOT-AHP approach, focus group discussions were conducted to examine the perceptions of researchers and extension workers about the adoption of agroforestry in Seychelles. The results indicated that the positive aspects of smallholder agroforestry outweigh the negative aspects. For example, increased agricultural production, control runoff and soil erosion receive the highest scores among the strength factors perceived by researchers and extension workers, respectively. The willingness of international organizations to fund agroforestry-related projects and the existence of native tree species on farmlands have the highest scores among the opportunity factors. The lack of education, information, and communication between the government and farmers, and the small land size and crop competition have the highest scores among the weakness factors. Lastly, change in government policies on land use has the highest score among the threat factors by researchers, whereas the most significant threat is climate change and variability for the extension workers. The provision for a thirty-year land lease agreement in the National Agroforestry Policy of Seychelles is viewed by both groups as an incentive that could potentially drive the adoption and acceptability of agroforestry. Furthermore, better coordination of various efforts to promote agroforestry and more substantial extension services for farmers, especially the role of technologies for optimal production on small plots of land, can enhance climate resilience in Seychelles and other small island developing states.

Multi-Dimensional Surface Water Quality Analyses in the Manawatu River Catchment, New Zealand

Land Use and Land Cover (LULC) properties give vital information about pollution signatures in rivers, and they help develop best management practices (BMPs) for effective water resource management. This work employs multivariate statistical methods, receptor modeling, connectivity analysis, and univariate trend analysis to investigate pollution sources across spatiotemporal scales in the Manawatu River, New Zealand. A positive matrix factorization (PMF) method was applied to interpret possible contamination sources. A 25-year dataset (1989–2014) comprising 12 water quality variables from three sites was used. Runoff connectivity analyses identified high-producing grassland (HG) as the most dominant pollution class in all sub-catchments. Univariate analyses revealed that nutrients and sediments were higher than in the initial monitoring years. The PMF analysis found possible pollutants causing impairment, which required attention from waste managers. PMF also showed that point, natural, and agricultural sources significantly contributed to pollution downstream of the river. In the midstream, the erosion, point, and agricultural sources were significant contributing factors. Agricultural pollution and soil erosion were the main contributors to the upstream sub-catchment area. This study suggests that BMPs with a high retention capacity are needed in specific locations in the catchment area to filter high concentrations of pollutants generated.

Characteristics of the Sediment Transport Process in Vegetation Hillslopes under Different Flow Rates

Vegetation filter strips (VFSs) have always been an important measure to control agricultural soil erosion, especially in mountainous and hilly areas with more sloping farmland. To investigate the mechanism of the sediment-trapping process by VFSs, a series of tests were conducted with four gradients of flow rate, 7.5–45 L min−1 m−1, and two different sediment concentrations of 40 and 120 g L−1. The whole process of overland flow was monitored, and sediment and particle size samples from the inflow and outflow were collected and measured. The results showed that the changes in sediment concentration did not significantly affect the corresponding coefficients in the power function relationship between overland flow rate and velocity. Using the Reynolds number alone cannot effectively indicate the flow pattern of overland flow on vegetation hillslopes. The peak particle size and linear function were effective in describing the relationship between sediment particle composition and delivery rate during the sediment-trapping process by VFSs. During the sediment-trapping process, the sediment-trapping capacity of VFSs continued to decrease. The increase in sediment discharge was accompanied by a higher proportion of coarse particles. Under the same flow rate conditions, when the sediment concentration was higher, the coarse particles and their proportion also increased faster. Therefore, using only a certain particle size threshold to distinguish suspended and transported sediment may lead to inaccurate estimation of the sediment-trapping performance of VFSs. This study deepened the understanding of the mechanism of water–sediment processes on vegetation hillslopes and promoted the widespread and efficient application of VFSs management technology.

Escaping social–ecological traps through ecological restoration and socioeconomic development in China's Loess Plateau

Abstract The social–ecological trap is an emerging concept that describes situations in which self‐reinforcing social and ecological feedbacks maintain or push a social–ecological system towards an undesirable state and threaten the sustainability of human societies. Understanding a system's feedback loops and identifying the leading factors of such traps is essential to develop effective management strategies to warn, avoid and escape traps. To better understand the dynamics of social–ecological traps, we developed a quantitative diagnostic framework that combines the social–ecological network approach and composite system state index. We demonstrated the effectiveness of the framework by examining the rural social–ecological evolution in China's Loess Plateau (LP) from 1949 to 2020, an area once faced with severe social–ecological challenges such as soil erosion, land degradation and poverty. Our analysis identified three stages of trap dynamics in LP: locked in the trap (1949–1981), reacting to the trap (1981–2003) and escaping the trap (2003–2020). In the first stage, LP was locked into an undesirable trajectory where reinforcing feedback occurs between rapid population growth, limited livelihood opportunities, excessive reliance on agriculture and severe soil erosion. Our results also found that the LP has made significant progress in escaping this social–ecological trap during the 21st century through ecological restoration practices and socioeconomic development. Similar social–ecological traps are also observed in many other regions of the world, particularly in developing countries. Our analysis recommends three pathways for addressing social–ecological traps in the LP: (1) promoting urbanization and livelihood diversity, (2) implementing site‐specific engineering measures (e.g. terraces and check dams in the LP) and (3) investing in ecological restoration programs. Escaping the trap is not the end of the story, but could be an early stage of another trap. Policymakers and managers should keep assessing and monitoring the policy practices and outcomes to avoid entering new trap situations. Read the free Plain Language Summary for this article on the Journal blog.

The Future of Soils in the Midwestern United States

AbstractSoil is the source of the vast majority of food consumed on Earth, and soils constitute the largest terrestrial carbon pool. Soil erosion associated with agriculture reduces crop productivity, and the redistribution of soil organic carbon (SOC) by erosion has potential to influence the global carbon cycle. Tillage strongly influences the erosion and redistribution of soil and SOC. However, tillage is rarely considered in predictions of soil erosion in the U.S.; hence regionwide estimates of both the current magnitude and future trends of soil redistribution by tillage are unknown. Here we use a landscape evolution model to forecast soil and SOC redistribution in the Midwestern United States over centennial timescales. We predict that present‐day rates of soil and SOC erosion are 1.1 ± 0.4 kg ⋅ m−‐2 ⋅ yr−‐1 and 12 ± 4 g ⋅ m−2 ⋅ yr−1, respectively, but these rates will rapidly decelerate due to diffusive evolution of topography and the progressive depletion of SOC in eroding soil profiles. After 100 years, we forecast that 8.8 (+1.9/−2.1) Pg of soil and 0.17 (+0.03/−0.04) Pg of SOC will have eroded, causing the surface concentration of SOC to decrease by 4.4% (+0.9/−1.1%). Model simulations that include more widespread adoption of low‐intensity tillage (i.e., no‐till farming) determine that soil redistribution, SOC redistribution, and surficial SOC loss after 100 years would decrease by ∼95% if low‐intensity tillage is fully adopted. Our findings indicate that low‐intensity tillage could greatly decrease soil degradation and that the potential for agricultural soil erosion to influence the global carbon cycle will diminish with time due to a reduction in SOC burial.

A New Idea to Improve the Test Method of Soil Aggregate Stability for Soils with a Texture Gradient

It is of great significance to determine soil aggregate stability in predicting agricultural production conditions and soil erosion risk. However, the problem exposed in the process of evaluating soil aggregate stability cannot be ignored: Can the effects of different mechanisms on the degree of soil aggregate breakdown be distinguished by selecting ethanol and water as dispersion media? Based on this question, natural soils with a gradient in soil textures of silty loam to loamy clay were used as the test materials. Deionized water, ethanol and hexane were employed as soaking solutions to quantitatively analyze the extent to which the aggregates were dispersed in static disintegration experiments. The results suggested that the soil hydrophilicity (SH) of six soils with a texture gradient were &gt;1 by comparing the aggregate breakdown index (ABI) of soils undergoing ethanol and hexane dispersion. This indicated that the hydrophilic group (-OH) contained in ethanol interacted with the hydrophilic surfaces of the soil particles. Therefore, the soil hydrophilicity (hydration) should be determined by comparing the ABI values undergoing hexane and water dispersion. From silty loam to loamy clay, the average contribution of hydration to aggregate fragmentation decreases, and the process of aggregate breakdown with different textures is characterized by size selectivity. When the soil aggregates were fragmented into 2–0.25 mm aggregate fractions, for silty loam and sandy clay loam, 0.002–0.02 mm and &lt;0.002 mm particles were preferentially moved; for clay loam and loamy clay, &gt;0.002 mm particles were preferentially moved. When the soil aggregates were fragmented into &lt;0.25 mm aggregate fractions for soils with different textures, the 0.002–0.02 mm and &lt;0.002 mm particles all exhibited preferential migration characteristics. This work provides an idea for improving the methods of aggregate stability measurements in the future.

The role of conventional tillage in agricultural soil erosion

Conventional tillage refers to the tillage process, especially the spring and autumn plowing process in which all the soil surface layer is disturbed, generally tilling approximately 20 cm deep. Conventional tillage is still widely used in sloping land, which leads to serious soil erosion and land degradation. The effect of tillage on soil erosion is defined by Tillage factor (T) in the model. The purpose of this study is to analyze the effect of conventional tillage on soil erosion and to calculate the value of the conventional tillage Factor T. The values of the conventional tillage factor (T value) were calculated for different soil and water conservation zones in China by collecting published literature and plot measurements from unpublished monitoring sites. The results showed that (1) the tillage factors of conventional tillage in China ranged from 0.27 to 0.55, with the largest being the North earth-stony region, the smallest being the Qinghai-Tibet plateau region, and the other six regions, namely, the Northeastern mollisol, the Northern wind erosion, the Northwest Loess Plateau, the South red soil, the Southwestern purple soil and the Southwestern karst region, were 0.34, 0.28, 0.53, 0.37, 0.35 and 0.29, respectively. In the regional soil erosion evaluation, the values can be taken by each of the eight main erosion type regions. (2) In the water erosion area except for the northeast, there is an obvious northsouth difference in the distribution of the T value, showing a decreasing trend from north to south. In practical use, the T value of the corresponding latitude area can be determined according to the Equation T = 0.2351φ- 0.02225, where φ is the latitude (°). (3) The T values of contour tillage, no-till, and monopoly tillage measures are significantly lower than the T values of conventional tillage, which have significant soil and water conservation benefits. The study initially determined the conventional tillage T values for each water conservation subzone, which can provide basic parameters for soil loss prediction on sloping land.

Evaluation of RUSLE and spatial assessment of agricultural soil erosion in Finland

Agricultural soil erosion has negative effects on surface water quality and aquatic ecosystems. A major impediment to agricultural erosion management in Finland has been the lack of high-resolution country-scale data on the spatial distribution of erosion. As a result, erosion mitigation measures have been targeted with limited information. Therefore, we evaluated the performance of the widely used RUSLE model against measurements from experimental fields, used the model to produce a two-metre resolution crop and management independent erosion estimate for all agricultural lands of Finland, and analysed erosion over different spatial scales. RUSLE showed skill (R2 = 0.76, NSE = 0.72) in estimating the observed erosion at experimental fields (55–2100 kg ha−1 yr−1) but with large errors (mean: −134 kg ha−1 yr−1, 90% range: −711 and 218 kg ha−1 yr−1). The evaluation, however, suggests that RUSLE performs similarly in Finland as elsewhere. The analysis of the developed country-scale data, in turn, revealed high erosion regions, and it showed how erosion varies between sub-catchment and between and within field parcels. For example, high-erosion areas concentrated in the proximity of water bodies were identified at the sub-catchment and within-field parcel scales. Altogether, the results demonstrate the predictive skill of RUSLE in high-latitude conditions, fill the earlier data gap in country-scale erosion, provide information for targeting erosion mitigation measures, and considerably improve the understanding of the spatial distribution of erosion in Finland.

A multi-millennial reconstruction of gully erosion in two contrasting Mediterranean catchments

Cereal and olive cultivation are thought to have played a major role in triggering soil erosion since humans have settled in the south of Spain and in increasing gully activity since the relatively recent intensification of olive cultivation. To test these hypotheses, we dated the sediments and reconstructed the soil erosion history of two gullied catchments, in Baena and Montefrío, both located in the South of Spain but with well differentiated land management histories. To date the sediments, we established a multi-proxy chronostratigraphy based on radiocarbon dating, optical stimulated luminescence and archaeology. In addition, we used the reconstructed land management history of the two catchments and aerial photographs. The reconstructed soil histories of the two catchments suggest a close link between agricultural land management practices and soil erosion in the last seven millennia. Notably, results indicate that soil erosion activity started earlier in Montefrío, corresponding to the first human settlements seven millennia ago. However, in the last two millennia erosion and gully activity in Baena have rapidly overtaken that of the Montefrío due to a more intense economic and agricultural activity of the former. In the last decades, erosion and gully activity in both catchments have been very high due to the intensification of the olive cultivation.

Long-Term (1990–2013) Changes and Spatial Variations of Cropland Runoff across China

Quantitative information on regional cropland runoff is important for sustainable agricultural water quantity and quality management. This study combined the Soil Conservation Service Curve Number (SCS-CN) method and geostatistical approaches to quantify long-term (1990–2013) changes and regional spatial variations of cropland runoff in China. Estimated CN values from 17 cropland study sites across China showed reasonable agreement with default values from the National Engineering Handbook (R2 = 0.76, n = 17). Among four commonly used geostatistical interpolation methods, the inverse distance weighting (IDW) method achieved the highest accuracy (R2 = 0.67, n = 209) for prediction of cropland runoff. Using default CN values and the IDW method, estimated national annual cropland runoff volume and runoff depth in 1990–2013 were 253 ± 25 km3 yr−1 and 182 ± 15 mm yr−1, respectively. Estimated cropland runoff depth gradually increased from the drier northwest inland region to the wetter southeast coastal region (range: 2–1375 mm yr−1). Regionally, eastern, central and southern China accounted for 39% of the cultivated area and 53% of the irrigated land area and contributed to 68% of the national cropland runoff volume. In contrast, northwestern, northern, southwestern and northeastern China accounted for 61% of the cultivated area and 47% of the irrigated land area and contributed to 32% of the runoff volume. Rainfall was the main source (72%) of cropland runoff for the entire nation, while irrigation became the main source of cropland runoff in drier regions (northwestern and southwestern China). Over the 24-year study period, estimated cropland runoff depth showed no significant trends, whereas cropland runoff volume and irrigation-contributed percentages decreased by 7% and 35%, respectively, owing to implementation of water-saving irrigation technologies. To reduce excessive runoff and increase water utilization efficiencies, regionally specific water management strategies should be further promoted. As the first long-term national estimate of cropland runoff in China, this study provides a simple framework for estimating regional cropland runoff depth and volume, providing critical information for guiding developments of management practices to mitigate agricultural nonpoint source pollution, soil erosion and water scarcity.

ПРОТИВОЭРОЗИОННАЯ МЕЛИОРАЦИЯ В РЕСПУБЛИКЕ ТАТАРСТАН

One of the most acute problems of agriculture in the Republic of Tatarstan in modern conditions is the progressive degradation of soil cover. Every year the scale of water erosion increases, causing huge damage not only to agriculture, but also to large and small rivers of the region. The territory of the republic is characterized by a large dissection, which serves as the basis of soil erosion. The research was carried out to analyze the impact of soil erosion on the efficiency of agricultural production and the development of science-based measures to combat soil erosion in agriculture of the Republic of Tatarstan. In general, in the subject of the Federation it is necessary to carry out erosion control works on the area of more than 2 million hectares of agricultural land. Every year spring melt water and storm water runoff on average washes away up to 22 tons of fertile soil from one hectare of arable land, which leads to an annual loss of up to 700 thousand tons of humus in the scale of the Republic of Tatarstan. This is comparable to the introduction of 10 million tons of organic fertilizers. Complex of anti-erosion measures depending on the relief and objective conditions of terrain includes organizational-economic, agromeliorative, forest-meliorative and hydromeliorative works, which ensure effective regulation of storm and melt water runoff, increase moisture reserve in soil cover and reduce washout of fertile soil layer, prevent new and expansion and spread of existing erosion centers and thereby contribute to improvement of fertility of agricultural lands. Thus, in the course of scientific research it is established that on average in the Republic of Tatarstan one set of anti-erosion measures protects up to 120 hectares of land from further development of erosion processes. The cost of the complex of anti-erosion measures, including anti-erosion pond - 2.5 million rubles, the payback period is 2 years.

A large geographic-scale characterization of organochlorine pesticides (OCPs) in surface sediments and multiple aquatic foods of inland freshwater aquaculture ponds in China: Co-occurrence, source and risk assessment

Inland freshwater aquaculture ponds (IFAPs) represent the key component of the global lentic freshwater environment and are increasingly important for global aquaculture production, yet the occurrence of organochlorine pesticides (OCPs) in these pond systems remains largely unknown. Here, we characterized the residual concentrations of 19 individual OCPs in sediments and in cultured fish and crustacean species (crabs, shrimp, crayfish and lobster), which were on-spot sampled from the IFAPs at a large region-scale in China. The total OCP levels in sediments varied dramatically between regions. Crabs presented the greatest OCP contamination among the studied species. Dichlorodiphenyltrichloroethanes (DDTs) was the dominating contaminant in sediments and crabs and its stable degradation products 4,4′-DDE and 4,4′-DDD were co-occurrent between these two compartments. The diagnostic ratio analysis indicated fresh inputs of DDTs, lindane and aldrin in multiple regions, which may be resulted from agricultural soil erosion, surface runoff and local anthropogenic activities. Ecological impacts of these pesticides could be expected at some sites due to their levels in sediments above the risk level. Risk assessment based on the OCP levels corrected by the cooking loss revealed that daily consumption of the IFAPs-derived aquatic foods may pose carcinogenic risks in humans.

Comparison of a laser precipitation monitor, piezoelectric transducer and particle imaging transient visual measurement technology under simulated rainfall in laboratory conditions

• Three instruments were compared in the lab under simulated rainfall conditions. • The raindrop size was most accurately described using the geometric mean diameter. • The raindrop visual measurement method could provide accurate raindrop shapes. • The laser precipitation monitor was more sensitive to measuring raindrops of < 1 mm. • Based on rainfall tests, the applicability of the three instruments was discussed. Precipitation microphysics, which describes the basic characteristics of rainfall, is important for agricultural praxis, weather prediction, aviation safety, and soil erosion prediction. In this study, three types of instruments (a laser precipitation monitor, LPM; piezoelectric transducer, PT; and particle imaging transient visual measurement technology, PIV) were employed to measure and compare the raindrop size distribution (DSD) and rainfall kinetic energy rate ( KE t ) under simulated rainfall conditions. Comparisons of the results indicated that under the same simulated rainfall conditions, the number of raindrops per unit area measured by LPM was larger than that measured by PIV. The DSD measured by PIV was more uniform than that of the PT and LPM under the same rainfall conditions. The raindrop size range measured by the LPM was smaller than that measured by the PT and PIV. In addition, the geometric mean diameter was a more accurate representation of raindrop size because PIV can capture the true irregular shape of raindrops. Compared to the PIV sensor, the LPM underestimates the raindrop diameter. The median raindrop diameter measured and calculated by PIV using the geometric mean diameter was approximately 1.61 times that of LPM. The KE t values measured by PIV and PT were approximately similar, while the KE t calculated by LPM was 0.51 and 0.57 times that of PIV and PT for the same rainfall conditions, respectively. A correction factor of 1.75 provided an approximate reference for the calibration of the kinetic energy calculation of the LPM instrument. The above results can provide basic insights for calibration and application of the three instruments.