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Soil erosion and associated sediment redistribution are key environmental problems in Central Argentina. Specific land uses and management practices, such as intensive grazing and crop cultivation, are considered to be significantly driving and accelerating these processes. This research focuses on the identification of suitable soil tracers from hot spots of land degradation and sediment fate in an agricultural catchment of central Argentina with erodible loess soils. Using Energy Dispersive X-Ray Fluorescence (EDXRF), elemental concentrations were determined and later used as soil tracers for geochemical characterization. The best set of tracers were identified using two artificial mixtures composed of known proportions of soil sources collected from different lands having contrasting soil uses. Barium, calcium, iron, phosphorus, and titanium were identified for obtaining the best suitable reconstruction of source proportions in the laboratory-prepared artificial mixtures. Then, these elements, as well as the total organic carbon, were applied for pinpointing critical hot spots of erosion within the studied catchment. Feedlots were identified to be the main source of sediments, river banks and dirt roads together are the second most important source. This investigation provides key information for optimizing soil conservation strategies and selecting land management practices and land uses which do not generate great contribution of sediment, preventing pollution of the waterways of the region.

High rates of potassium (K) fertilisation are used in arable soils affected by the Fukushima Daichii Nuclear Power Plant accident of 2011, in order to further reduce the uptake of radiocaesium (RCs) by plants. Additionally, zeolite has been applied to decrease soil solution RCs following topsoil removal. However, there is uncertainty on the role of zeolite in the uptake of RCs in Japanese soils. In this study, we compared RCs sorption in three soils with major differences in clay mineralogy: a Cambisol rich in vermiculite with strong retention of monovalent cations; an Andosol with very low 2:1 phyllosilicate content and with low K and Cs affinity; and a clay-rich, lowland smectitic Gleysol with high water holding capacity. We elucidated their solid-liquid distribution of K and 133Cs (as a proxy for RCs) in response to K addition as simulating K fertilisation, and also to zeolite (clinoptilolite) addition. The Radiocaesium Interception Potential (RIP), which is a key parameter that determines the RCs selectivity in soil and its phytoavailability, was analysed by spiking 1 g of soil with 1-2 KBq of 134Cs followed by a determination of solution 134Cs. The data were used to predict the soil-to-plant transfer factor (TF) based on a simplified version of the current RCs TF model. Our results showed that the vermiculitic soils had the lowest increase in exchangeable K (ex-K) at a given K dose, given its strong fixation in the 2:1 phyllosilicate layers, as opposed to the Andosol. Zeolite addition was shown to increase most of the soils RIP and thus proved its ability to adsorb RCs. Besides, zeolite addition also diminished both soil solution Cs (Csss) and K (Kss) concentrations for the allophanic Andosol. The K and Cs selectivity of the soil increased by zeolite addition, thus KSS, crucial for RCs uptake, consequently declined. This decrease observed for KSS would be a reason for the reported ineffectiveness of zeolite application in previous studies. Solid-liquid distribution coefficients for exchangeable Cs (ex-Cs) suggest that the extraction determined by with 1M ammonium acetate does not constitute a reliable proxy for RCs as compared to CsSS. At low KSS range (—1), our findings for the vermiculitic and smectitic soils showed a rapid increase of CsSS. This sharp increase was not foreseen in the currently defined RCs model of Absalom et al. (1999 and ulterior). It entails, according to our predictions, a clear underestimation of the TF in the model and therefore a higher risk of RCs transfer to crops than expected in the Fukushima Prefecture vicinities -if the ongoing K fertilisation scheme is discontinued. Additionally, our comparisons of the predicted TF based on KSS and ex-K showed that KSS may be used as a more precise parameter to assess zeolite amendments in Japanese soils.

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) aftermath in 2011, potassium addition has been increasingly valued as the most effective countermeasure for soil remediation of polluted sites. Potassium is a competing cation with caesium during plant root uptake. Recent studies have elucidated that potassium application can increase the Radiocaesium Interception Potential (RIP), a key parameter that determines the radiocaesium selectivity in soil and therefore its phytoavailability. The RIP is determined as the product of the distribution coefficient of caesium and the concentration of potassium in soil solution, considering the occupation in exchange regular sites but especially in the so-called frayed-edged of the 2:1 phyllosilicate layers of clay minerals, that account for most of the high-selectivity sites for caesium. In order to increase soil RIP, mineral amendments -especially zeolite- were applied in Japanese target fields as a major measure for safe agricultural production. In this study, we aimed at the determination of the RIP of Japanese and European soils with different clay mineralogy, as a key parameter for the solid-liquid distribution of radiocaesium in soils. To do so, we analysed the clay mineralogy of soils by X-Ray diffraction (XRD), as well as the solid and soil solution phases of five types of soils with different potassium fixing capacity by atomic absorption spectrometry (AAS) and ionic chromatography (IC), respectively. As potassium fixation varies among soils, we expected very different relationships between their potassium content and RIP. Their RIP was determined by spiking with 1-2 KBq of radiocaesium-134 prior to the use of thallium doped sodium iodine scintillator (NaI(Tl)). Both solid phase exchangeable caesium and soil solution caesium were analysed by inductively coupled plasma mass spectrometry (ICP-MS). Partial findings for Japanese soils showed a potassium fixing rate of approximately 93% for vermiculitic soils, while for imogolitic Andosols with low 2:1 phyllosilicate clay mineral content, only 17% of potassium addition was determined to be fixed. The fixation capacity for smectitic soils reached 57%. Furthermore, additional research is currently being done regarding RIP determination of several agricultural soils and with and without zeolite amendments. The final results will be shown in the EGU General Assembly 2020.

2 Pags. with a extended abstract. © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License., Our results show that combination of 137Cs derived information with data from nutrients pools can be an important aid for interpreting changes in paraglacial landscapes where soils are forming on recently exposed glacial deposits.

The Andean glaciers are experiencing since 1980 an accelerated decline associated with an increase in air temperature across the region. Encompassing the shrinking of mountain glaciers new soils are formed as deglaciation facilitates biogeochemical processes and the subsequent development of vegetation. Under extreme environmental conditions high-altitude soils are constrained by climate, substrate and geomorphological characteristics of recently deglaciated surfaces that control soil features in high mountains. At the foot of Huayna-Potosí, the glacier retreat is gradually exposing mineral substrate, which is being colonised by soil biota and plants. The subsequent accumulation of organic matter is progressing rapidly especially in wetlands developed in the proglacial area thus accelerating the processes of soil formation. The characterization of soil organic carbon (SOC) pools is necessary to understand SOC dynamics in soils and a relative measure of C stability in soils.In this study we attempt to evaluate the distribution of SOC, C fractions and nitrogen in glacial deposits and high altitude wetlands to relate it with that of 137Cs as indicator of soil stability. To this purpose topsoil sampling of moraines, colluvium and peat soil in wetlands was undertaken during a two weeks expedition to Huayna-Potosí Glacier area in the frame of IAEA INT5153 project in May 2017 and contents of SOC and its fractions (i.e. active and stable carbon fractions), nitrogen and 137Cs activity (Bq kg-1) were determined.The high wetlands both at favourable flat topographic positions and slopes have high organic rich soils showing large carbon sink capacity. More abundant depleted values of 137Cs in moraines and colluvium indicate greater impact of soil erosion processes in comparison to wetlands, whereas a higher 137Cs content is related to higher carbon contents and more abundant vegetation that would preserve soil from erosion. The size of the nutrient pool such as carbon and nitrogen is much higher in wetlands than in glacial deposits. In the carbon pool, the active fraction is more abundant than the stable fraction but in wetlands the ratio active/stable is much higher (mean: 31) than in glacial deposits (mean: 5). The contribution of the active fraction to SOC is also higher in wetlands (c.a. 1), while the opposite was found for the stable fraction contribution to SOC with almost a ratio of 0 in wetlands compared to 0.24 in glacial deposits. Paralleling the evolution of vegetation the enrichment in soil nutrients affects carbon (C) dynamics in the new soils that all are in the early forming stages with low C stability. Despite wetlands soils having the largest SOC content, the imbalance in the proportions of the C fractions with almost negligible stable C evidence the risk of interrupting the C cycle by loosing the more labile fraction. Therefore, focus should be directed to preserve the fragile new forming soils but specially wetlands because their key role in regulating the hydrological system and maintaining high altitude ecosystems.

Large-scale deforestation, intensive land use and unfavourable rainfall conditions are responsible for significant continuous degradation of the Haitian uplands. To develop soil conservation strategies, simple and cost-effective methods are needed to assess rates of soil loss from farmland in Haiti. The fallout radionuclide caesium-137 (137Cs) provides one such means of documenting medium-term soil redistribution rates. In this contribution, the authors report the first use in Haiti of 137Cs measurements to document soil redistribution rates and the associated pattern of erosion/sedimentation rates along typical hillslopes within a traditional upland Haitian farming area. The local 137Cs reference inventory, measured at an adjacent undisturbed flat area, was 670 Bq m−2 (SD = 100 Bq m−2, CV = 15%, n = 7). Within the study area, where cultivation commenced in 1992 after deforestation, three representative downslope transects were sampled. These were characterized by 137Cs inventories ranging from 190 to 2200 Bq m−2. Although, the study area was cultivated by the local farmers, the 137Cs depth distributions obtained from the area differed markedly from those expected from a cultivated area. They showed little evidence of tillage mixing within the upper part of the soil or, more particularly, of the near-uniform activities normally associated with the plough layer or cultivation horizon. They were very similar to that found at the reference site and were characterized by high 137Cs activities at the surface and much lower activities at greater depths. This situation is thought to reflect the traditional manual tillage practices which cause limited disturbance and mixing of the upper part of the soil. It precluded the use of the conversion models normally used to estimate soil redistribution rates from 137Cs measurements on cultivated soils and the Diffusion and Migration conversion model frequently used for uncultivated soils was modified for application to the cultivated soils of the study area, in order to take account of the unusual local conditions. The model was also modified to take account of the fact that cultivation in the study area commenced in 1992, rather than predating the period of weapons test fallout which extended from the mid 1950s to the 1970s. Erosion rates on the upper parts of the hillside involved in the study were found to be relatively high and ca. −23 t ha−1 y−1 with low spatial variability. In the lower, flatter areas at the bottom of the slope, deposition occurred. Deposition rates were characterized by high spatial variability, ranging from 6.0 to 71 t ha−1 y−1. Soil redistribution rates of this magnitude are a cause for concern and there is an urgent need to implement soil conservation measures to ensure the longer-term sustainability of the local agricultural practices. Fil: Velasco, Ricardo Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina Fil: Torres Astorga, Romina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina Fil: Joseph, D.. Faculté D'agronomie et de Médecine Vétérinaire; Haití. Ministère de L'agriculture; Haití Fil: Antoine, J. S.. Faculté D'agronomie et de Médecine Vétérinaire; Haití. Ministère de L'agriculture; Haití Fil: Mabit, L.. International Atomic Energy Agency; Austria Fil: Toloza, A.. International Atomic Energy Agency; Austria Fil: Dercon, G.. International Atomic Energy Agency; Austria Fil: Walling, Des E.. University of Exeter; Reino Unido

Identification of hot spots of land degradation is strongly related with the selection of soil tracers for sediment pathways. This research proposes the complementary and integrated application of two analytical techniques to select the most suitable fingerprint tracers for identifying the main sources of sediments in an agricultural catchment located in Central Argentina with erosive loess soils. Diffuse reflectance Fourier transformed in the mid-infrared range (DRIFT-MIR) spectroscopy and energy-dispersive X-ray fluorescence (EDXRF) were used for a suitable fingerprint selection. For using DRIFT-MIR spectroscopy as fingerprinting technique, calibration through quantitative parameters is needed to link and correlate DRIFT-MIR spectra with soil tracers. EDXRF was used in this context for determining the concentrations of geochemical elements in soil samples. The selected tracers were confirmed using two artificial mixtures composed of known proportions of soil collected in different sites with distinctive soil uses. These fingerprint elements were used as parameters to build a predictive model with the whole set of DRIFT-MIR spectra. Fingerprint elements such as phosphorus, iron, calcium, barium, and titanium were identified for obtaining a suitable reconstruction of the source proportions in the artificial mixtures. Mid-infrared spectra produced successful prediction models (R2 = 0.91) for Fe content and moderate useful prediction (R2 = 0.72) for Ti content. For Ca, P, and Ba, the R2 were 0.44, 0.58, and 0.59 respectively. Fil: Torres Astorga, Romina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina Fil: de los Santos Villalobos, Sergio. Universidad de Sonora; México. Consejo Nacional de Ciencia y Tecnología; México Fil: Velasco, Ricardo Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina Fil: Domínguez Quintero, Olgioly. Universidade Federal Fluminense; Brasil Fil: Pereira Cardoso, Renan. Universidade Federal Fluminense; Brasil Fil: Meigikos Dos Anjos, Roberto. Universidade Federal Fluminense; Brasil Fil: Diawara, Yacouba. United States Department of Energy; Estados Unidos Fil: Dercon, Gerd. International Atomic Energy Agency; Austria. Comisión Nacional de Energía Atómica; Argentina Fil: Mabit, Lionel. International Atomic Energy Agency; Austria

The cultivation of marginal land in the Andes makes it one of the hot-spots of soil erosion. Since the 1980s an alternative soil conservation method denominated “slow-forming terraces” has been introduced to the area, since it is not labour or cost intensive and therefore more likely to be applied by the small-holder farmers. Research investigating the short-term effect on soil properties and crop productivity in these terrace systems showed reason for concern regarding the sustainability of the method, since there were position-dependent drops in crop productivity and related soil properties especially on shallow soils. Here, we investigate in the same terrace systems the temporal change of the observed properties 21 years after establishment. The terraces are managed by subsistence farmers and thus provide a valuable insight: if the spatial heterogeneity disappears, this renders slow-forming terraces agronomically sustainable in the long-term. Our results show a significant improvement of soil properties in general and furthermore to most extent a disappearance of the spatial heterogeneity in plant properties. These findings outline that the initial disadvantages of this soil conservation practice can be overcome in the long-term making slow-forming terraces a valuable measure for soil conservation and a sustainable system for small-holder subsistence farming. A support in farm planning, informing about both short- and long-term agronomic effects, while also considering social, economic and cultural/traditional aspects, could increase the adoption and maintenance of conservation measures and also symbiotically increase family income.

Continuing cereal-based crop rotations such as rice–wheat, intensive cultivation and complete removal of postharvest crop residue (CR) for animal consumption and fuel, or its burning have reduced the organic matter content and productivity of irrigated semi-arid subtropical soils of South Asia. Identification of effective strategies for the management of tillage and CR could foster sustainable and environmentally sound agricultural systems. To this effect, a 4-year field experiment was established with annual soybean–wheat rotation under subtropical climate conditions in the Indo-Gangetic Plains of Northwestern India to evaluate the integrated effects of tillage, CR retainment, mineral fertilizers and farmyard manure (FYM) on crop production, nutrients uptake, soil moisture storage and temperature dynamics. The experimental soil was loamy sand, poor in organic C and low in available P. Sixteen treatment combinations involved recommended and 25% higher NP rates without or with 10 t FYM ha −1 and CR incorporated in conventional tillage (CT) and retained on the soil surface in conservation agriculture (CA) system. The results clearly revealed that (a) soybean yield was 2–6% higher in CA than CT in different treatments with and without CR, (b) significantly higher uptake of N and P by soybean from CR-amended treatments of both CT and CA, which reflected its effect in improving the soybean yield, (c) the current fertilizer NP recommendation of 20 kg N and 26 kg P ha −1 for soybean is not adequate and either application of 25% higher NP rate (25 kg N and 33 kg P ha −1 ) or additional 10 t FYM ha −1 is required for optimum crop production of ∼ 2500 kg ha −1 , (d) CA conserved more water in soil profile than CT, however, the differences in soil moisture storage in CT vis-a-vis CA were not reflected in soybean yield presumably due to frequent wetting of soil by heavy monsoonal rains, (e) the wheat yield was highest in both CT and CA systems when grown with the application of 150 kg N and 33 kg P ha −1 without CR and was 7% higher in CA (4140 kg ha −1 ) than CT (4048 kg ha −1 ), and (f) retention of CR on soil surface in winter-grown wheat under CA reduced wheat yield by 8–24% and N uptake by 3–5% as a consequence of mulching effects creating cooler environment in surface soil layer during initial 3 weeks after seeding, which led to the delayed germination and relatively poor crop growth during initial period.

In tropical mountainous regions of South East Asia, intensive cultivation of annual crops on steep slopes makes the area prone to erosion resulting in decreasing soil fertility. Sediment deposition in the valleys, however, can enhance soil fertility, depending on the quality of the sediments, and influence crop productivity. The aim of the study was to assess (i) the spatio-temporal variation in grain yield along two rice terrace cascades in the uplands of northern Viet Nam, (ii) possible linkage of sediment deposition with the observed variation in grain yield, and (iii) whether spatial variation in soil water or nitrogen availability influenced the obtained yields masking the effect of inherent soil fertility using carbon isotope ( 13 C) discrimination and 15 N natural abundance techniques. In order to evaluate the impact of seasonal conditions, fertilizer use and sediment quality on rice performance, 15 N and 13 C stable isotope compositions of rice leaves and grains taken after harvest were examined and combined with soil fertility information and rice performance using multivariate statistics. The observed grain yields for the non-fertilized fields, averaged over both cascades, accounted for 4.0 ± 1.4 Mg ha −1 and 6.6 ± 2.5 Mg ha −1 in the spring and summer crop, respectively, while for the fertilized fields, grain yields of 6.5 ± 2.1 Mg ha −1 and 6.9 ± 2.1 Mg ha −1 were obtained. In general, the spatial variation of rice grain yield was strongly and significantly linked to sediment induced soil fertility and textural changes, such as soil organic carbon ( r 0.34/0.77 for Cascades 1 and 2, respectively) and sand fraction ( r −0.88/−0.34). However, the observed seasonal alteration in topsoil quality, due to sediment deposition over two cropping cycles, was not sufficient to fully account for spatial variability in rice productivity. Spatial variability in soil water availability, assessed through 13 C discrimination, was mainly present in the spring crop and was linearly related to the distance from the irrigation channel, and overshadowed in Cascade 2 the expected yield trends based on sediment deposition. Although δ 15 N signatures in plants indicated sufficient N uptake, grain yields were not found to be always significantly influenced by fertilizer application. These results showed the importance of integrating sediment enrichment in paddy fields within soil fertility analysis. Furthermore, where the effect of inherent soil fertility on rice productivity is masked by soil water or nitrogen availability, the use of 13 C and 15 N stable isotopes and its integration with conventional techniques showed potential to enhance the understanding of the influence of erosion – sedimentation and nutrient fluxes on crop productivity, at toposequence level.

Soil erosion is a serious problem in the forest-savanna transition zone or derived savanna of West Africa and Nigeria and needs to be reduced to maintain soil quality and to ensure food security. In 2007, the use of the fallout radionuclide 137 Cs as a tracer for estimating the magnitude of medium-term (40–50 years) rates of soil redistribution was tested at a research station in Ibadan, Nigeria, to investigate, for the first time, its applicability in the derived savanna of West Africa. Because of the traditional tillage practice for cassava cultivation of creating downslope oriented ridges and furrows during the annual ploughing, there was a need to adapt the 137 Cs approach to these specific condition. The mean inventory was determined for cores collected from both ridges and furrows at different positions down the slope and this value was used to estimate the downslope variation in the longer term soil redistribution rate. The mean 137 Cs reference inventory obtained for an undisturbed site was 568 ± 138 Bq m −2 . The average inventory for the upper slope of the cassava field (423 ± 323 Bq m −2 ) was generally lower than the average inventory for the middle slope (509 ± 166 Bq m −2 ) and for the lower slope (606 ± 245 Bq m −2 ) and these results provided clear evidence of the downslope movement of soil. The mean 137 Cs inventory for the study area within the cassava field (496 ± 273 Bq m −2 ) was 13% lower than the reference inventory, indicating that some of the soil mobilised and redistributed by erosion had been exported beyond the field. Using 137 Cs data set and the conversion model mass balance model 2 (MBM2), the gross erosion rate from the cultivated site was estimated to be 18.3 t ha −1 year −1 and the net erosion rate 14.4 t ha −1 year −1 , providing a sediment delivery ratio of 78%. These estimates are comparable to the rates generated by conventional soil loss measurements made close to the study site. The study demonstrates that the 137 Cs technique can be successfully used to obtain data on medium-term soil redistribution in the derived savanna of Nigeria, and that it could be a useful tool for supporting the improvement of soil conservation on farmland in West Africa.

While water erosion has been the focus of past research in the Andes, former studies show that soil erosion could also be related to the methods used in cultivating the fields. The main objective of the present study was to assess (i) tillage erosion caused by the traditional animal-powered “yunta” or ard plough in the Andes and the factors controlling the process and (ii) the implications for soil conservation. Erosion rates were experimentally measured on 27 sites, having slopes from ca. 0% to 60% and soils ranging from Andosols to Cambisols, in the Andes region of Ecuador (Gima, Azuay). Different tillage methods were assessed: (i) tillage parallel to the contour lines (‘Paralelo’) and (ii) tillage at an angle with the contour lines. Statistical analysis points out that erosion caused by animal-powered tillage is gravity-driven. A strong correlation exists between slope and downslope displacement: furthermore, tillage depth and initial soil condition are important. For the ‘Paralelo’ tillage method the tillage transportation coefficient (k) is below 100 kg m− 1 Tillage Pass− 1, for the combined ‘Arado’–‘Cruzado’ tillage method k may exceed 300 kg m− 1. Tillage erosion is responsible for the reduction of the slope between the contour strips over a relatively short time period of 20 years, resulting in the formation of terraces and therefore the reduction of the water erosion risk. However, at the same time it may negatively affect soil quality.

In order to evaluate the sustainability and efficiency of soil carbon sequestration measures and the impact of different management and environmental factors, information on soil organic matter (SOM) stability and mean residence time (MRT) is required. However, this information on SOM stability and MRT is expensive to determine via radiocarbon dating, precluding a wide spread use of stability measurements in soil science. In this paper, we test an alternative method, first developed by Conen et al. (2008) for undisturbed Alpine grassland systems, using C and N stable isotope ratios in more frequently disturbed agricultural soils. Since only information on carbon and nitrogen concentrations and their stable isotope ratios is required, it is possible to estimate the SOM stability at greatly reduced costs compared to radiocarbon dating. Using four different experimental sites located in various climates and soil types, this research proved the effectiveness of using the C/N ratio and δ15N signature to determine the stability of mOM (mineral associated organic matter) relative to POM (particulate organic matter) in an intensively managed agro-ecological setting. Combining this approach with δ13C measurements allowed discriminating between different management (grassland vs cropland) and land use (till vs no till) systems. With increasing depth the stability of mOM relative to POM increases, but less so under tillage compared to no-till practises. Applying this approach to investigate SOM stability in different soil aggregate fractions, it corroborates the aggregate hierarchy theory as proposed by Six et al. (2004) and Segoli et al. (2013). The organic matter in the occluded micro-aggregate and silt & clay fractions is less degraded than the SOM in the free micro-aggregate and silt & clay fractions. The stable isotope approach can be particularly useful for soils with a history of burning and thus containing old charcoal particles, preventing the use of 14C to determine the SOM stability. publisher: Elsevier articletitle: Predicting soil organic matter stability in agricultural fields through carbon and nitrogen stable isotopes journaltitle: Soil Biology and Biochemistry articlelink: http://dx.doi.org/10.1016/j.soilbio.2015.05.011 content_type: article copyright: Copyright © 2015 Elsevier Ltd. All rights reserved. ispartof: Soil Biology & Biochemistry vol:88 pages:29-38 status: published

Many attributes of present day soils can only be explained by reference to land management in the historic past. This is particularly well expressed in the plaggen soils which occur extensively on the north European plain. These deepened soils owe their dominant characteristics to the application from the 12th century of turf materials, often impregnated with dung. Similar deepening of soils can result from the disposal of urban waste. This paper discusses the results of soil research focused on a small Scottish town (Nairn). A soil survey revealed topsoils of over 1 m overlying fluvioglacial sands and gravels; such deepening is explained by the use of town waste on the burgh's arable lands from at least the 17th century up until the mid-19th century when an integrated sewerage system was installed. Micromorphological study of this deepened topsoil revealed the presence of many small black carbonaceous particles. Oxygen:carbon ratios were calculated from microprobe results as a means of confirming the carbonaceous nature of these particles. Soil phosphorus was primarily concentrated on the perimeter of these particles. The high quality of present day soils on the edge of the town is explained by the disposal of waste material, which included much carbonised material. This paper is the first to highlight the importance and potential of examining the gradation in soils from urban to rural contexts.

The effect of land use on the water retention capacity of Umbric Andosols in south Ecuador was studied. The objective was to acquire a better insight into the hydrological processes of the ecosystem and the role of the soil, in order to assess the impact of changing soil properties due to land use change on the hydrology of the high Andes region. Field data on the water retention capacity at wilting point of Umbric Andosols were collected for both cultivated field conditions and original bush vegetation. The pH in water and in NaF, texture, organic matter content and dry bulk density were measured to show which physicochemical soil characteristics are responsible for the water retention of the Umbric Andosols and for the irreversible loss in water retention due to air drying. Organic matter content appears to be very important and certainly more important than allophane clay content. Water retention of the organic litter layer was calculated to be 16 mm, this would be lost when vegetation was cleared and the land cultivated.

Anthropogenic sandy soils in Scotland, Denmark and The Netherlands were studied to determine the extent to which they had been influenced by inputs of materials and current land management. Particle size distribution, pH, loss on ignition, ECEC, base saturation and total P were determined for eight profiles under different land uses (arable, meadow and woodland). Inputs of materials were identified by comparison of particle size distributions of the deepened cultivated horizons with those of parent materials. At all three sites turf derived from local sources was the main input though there were other mineral additions including an aeolian component. Overall, the anthropogenic soils are remarkably similar in field and some analytical properties, though land use has influenced pH, base saturation and total P.

Due to severe land degradation problems, soil conservation is a matter of major concern in the Ecuadorian Andes. Slow-forming terraces, a variation of hedgerow agro-forestry systems composed by contour grass barrier strips, can be considered as the most frequently used technique in Andean rural communities of Ecuador. However, due to shallow soils, terrace development often has the disadvantage causing gradients in soil properties from the upper to the lower elevations within the terrace. The main objectives of this study were to assess (i) spatial variability in soil properties on slow-forming terraces in the Andes and (ii) implications of variability for the management of this soil conservation technique. In order to measure spatial variability, soil sampling (0–15 cm) was carried out in bands following the contour, which were located every 1 m beginning at the highest point of elevation and including the lowest point on the terrace. Soil properties, such as pH(H2O), pH(NaF), organic carbon, total nitrogen, NO3−, P, K, exchangeable aluminium, P fixation, exchangeable bases, cationic exchange capacity, base saturation and texture, were monitored on eight terraces, having slopes from 15 to 30%, a length of 4–8 m and soils ranging from Cambisols to Phaeozems, in the Ecuadorian Andes (Gima, Azuay). Terraces, which were 2–4 years, were managed in a traditional or more intensified way (i.e. without or with the application of organic manure). Bufferstrips were composed by (i) Pennisetum clandestinum and Lolium multiflorum or (ii) Phalaris tuberosa. Spatial variability was analysed by stepwise multiple regression analysis, where position on the terrace was the independent variable and soil property was the dependent variable. Factor analysis was carried out in order to compare spatial variability patterns of the terraces and formulate management strategies. High spatial variability in soil properties was found. Although spatial variation was site dependent, it was clear that soil fertility increased from the upper to the lower part of the terraces. The present study shows that management strategy could influence the pattern and magnitude of spatial variation. Site-specific soil fertility improvement is suggested as means to combat variation caused by tillage erosion in slow-forming terraces. Cuenca volumen 72; número 1

Land management practices on tropical soils have been studied extensively during the past decades. However, assessments of their impact on field-scale spatial variability in crop performance are rare. A case of practices affecting spatial crop response at field level in a systematic way is the contour hedgerow system, a widespread soil conservation technique on steep lands in the tropics. The objectives of this study were to assess: (i) spatial variability in crop response under contour hedgerow systems in the Andes and (ii) implications for management of steep land alley farming. In order to measure spatial variability in crop response, Triticum aestivum was sown in rows following the contours, placed every 25 cm along the slope direction. Grain yield was monitored on eight alleys, having slopes from 15 to 30%, a length of 4–8 m and soils ranging from Dystri-Vertic Cambisols to Haplic Phaeozem, in the Andes region of Ecuador. In order to relate crop response with soil fertility, soil sampling was carried out in bands following the contour. Top soil properties, such as organic carbon, N Total , NO 3 − , P, exchangeable Aluminium, P fixation, exchangeable bases, CEC and texture, were analysed. The barrier strips of the contour hedgerow systems were composed of: (i) Pennisetum clandestinum and Lolium multiflorum or (ii) Phalaris tuberosa . Spatial variability in crop response was described by fourth-order polynomial equations, where position in the alley was the independent variable and plant characteristics were the dependent variables. Grain yield ranged from 0.8 to 4.0 t ha −1 (net area). Clear and significant patterns of spatial variability in crop response were found in all alleys, with R 2 varying from 0.55 to 0.90. Crop response was strongly and positively correlated with NO 3 − , P, exchangeable bases or organic carbon, dependent on the management, age and soil conditions of the alleys. Tillage erosion and soil accumulation on respectively the upper and lower elevations of the alleys were the main causes for a tendency to a significantly increased crop response along the slope direction. However, according the type of grass used in the barrier strip, competition for soil fertility and soil moisture occurred and influenced in negative way crop productivity in the lower elevations of the alleys. An index is proposed to assess the effect of contour hedgerows on crop response. The present study shows that contour hedgerow systems cannot always be evaluated as completely positive. Soil fertility improvement on the upper part of the alleys and a better management of the barrier strip are suggested to enhance crop productivity of contour hedgerow systems.