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11 Pags.- 4 Tabls.- 8 Figs., The present dominant trend of retreating and shrinking glaciers is leading to the formation of new soil in proglacial zones. The Cordillera Blanca located in the Peruvian Andes includes the Lake Parón catchment known for the Artesonraju Glacier and its rapid retreat, forming the largest proglacial lake in the region. This work aims to gain knowledge of soil and vegetation development on the most representative proglacial landforms existing in the Parón catchment. Previous research in proglacial environments suggests that soil properties might indicate different ages of ice retreat besides the normalised difference vegetation index (NDVI), which is known to be a powerful tool for assessing vegetation development. In the area surrounding Lake Parón up to the glacier tongue, an altitudinal transect (4200–4700 m a.s.l.) was established for sampling topsoils. A total of 40 surface soil samples (0–3 cm) were collected from the main glacial landforms, moraines, colluvium, glacio-fluvial terraces and alluvial fans, developed after different stages of glacier retreat. Soil organic carbon (SOC) and SOC fractions (active and stable), total nitrogen (TN) and 137Cs were analysed. A multitemporal analysis of NDVI was performed to assess the vegetation dynamics in the Parón catchment and over the different glacial landforms over time (1987–2018). The NDVI increase in recent decades indicates an expansion of vegetation cover and density. We compared NDVI values with the SOC and TN content to assess the relationships with vegetation growth in mountain soils. NDVI and the distribution of SOC and TN content show a positive correlation between vegetation evolution and the enrichment in soil nutrients that are more abundant in older moraines in coincidence with highest NDVI. These results outline the effect of shrinking mountain glaciers on generating new soils in parallel with the growth of vegetation., This study was supported by the IAEA Technical Cooperation Programme through the INT/5/153 project “Assessing the Impact of Climate Change and its Effects on Soil and Water Resources in Polar and Mountainous Regions” and by the Spanish National Project CGL2014-52986-R.

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 present dominant trend of retreating and shrinking glaciers is leading to the formation of new soil in proglacial zones. The Cordillera Blanca located in the Peruvian Andes includes the Lake Parón catchment known for the Artesonraju Glacier and its rapid retreat, forming the largest proglacial lake in the region. This work aims to gain knowledge of soil and vegetation development on the most representative proglacial landforms existing in the Parón catchment. Previous research in proglacial environments suggests that soil properties might indicate different ages of ice retreat besides the normalised difference vegetation index (NDVI), which is known to be a powerful tool for assessing vegetation development. In the area surrounding Lake Parón up to the glacier tongue, an altitudinal transect (4200-4700 m a.s.l.) was established for sampling topsoils. A total of 40 surface soil samples (0-3 cm) were collected from the main glacial landforms, moraines, colluvium, glacio-fluvial terraces and alluvial fans, developed after different stages of glacier retreat. Soil organic carbon (SOC) and SOC fractions (active and stable), total nitrogen (TN) and

In soil redistribution studies employing 7Be, the radionuclide inventories and their spatial uniformity in soil can be influenced by the crop coverage conditions. A relatively high 7Be interception factor, normalized to the leaf area index (LAI), of 0.61 ± 0.08 (LAI value 0.87 ± 0.06) was determined after 0.4 mm precipitation. After a second 7.2 mm rainfall, the interception factor had a value of 0.36 ± 0.04, for 0.30 ± 0.02 LAI value. Wash-off experiments with deionized water showed that the released 7Be fraction was limited within a range of 29–37 % of the initial concentration of leaf deposit.

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 (R

Land degradation is a problem affecting the sustainability of commercial forest plantations. The identification of critical areas prone to erosion can assist this activity to better target soil conservation efforts. Here we present the first use of the carbon-13 signatures of fatty acids (C14 to C24) in soil samples for spatial and temporal tracing of sediment transport in river bodies of upland commercial forest catchments in Chile. This compound-specific stable isotope (CSSI) technique was tested as a fingerprinting approach to determine the degree of soil erosion in pre-harvested forest catchments with surface areas ranging from 12 to 40ha. For soil apportionment a mixing model based on a Bayesian inference framework was used (CSSIAR v.2.0). Approximately four potential sediment sources were used for the calculations of all of the selected catchments. Unpaved forestry roads were shown to be the main source of sediment deposited at the outlet of the catchments (30-75%). Furthermore, sampling along the stream channel demonstrated that sediments were mainly comprised of sediment coming from the unpaved roads in the upper part of the catchments (74-98%). From this it was possible to identify the location and type of primary land use contributing to the sediment delivered at the outlet of the catchments. The derived information will allow management to focus efforts to control or mitigate soil erosion by improving the runoff features of the forest roads. The use of this CSSI technique has a high potential to help forestry managers and decision makers to evaluate and mitigate sources of soil erosion in upland forest catchments. It is important to highlight that this technique can also be a good complement to other soil erosion assessment and geological fingerprinting techniques, especially when attempting to quantify (sediment loads) and differentiate which type of land use most contributes to sediment accumulation.

Compound-specific stable isotope (CSSI) fingerprinting of sediment sources is a recently introduced tool to overcome some limitations of conventional approaches for sediment source apportionment. The technique uses the 13C CSSI signature of plant-derived fatty acids (δ13C-fatty acids) associated with soil minerals as a tracer. This paper provides methodological perspectives to advance the use of CSSI fingerprinting in combination with stable isotope mixing models (SIMMs) to apportion the relative contributions of different sediment sources (i.e. land uses) to sediments. CSSI fingerprinting allows quantitative estimation of the relative contribution of sediment sources within a catchment at a spatio-temporal resolution, taking into account the following approaches. First, application of CSSI fingerprinting techniques to complex catchments presents particular challenges and calls for well-designed sampling strategies and data handling. Hereby, it is essential to balance the effort required for representative sample collection and analyses against the need to accurately quantify the variability within the system. Second, robustness of the CSSI approach depends on the specificity and conservativeness of the δ13C-FA fingerprint. Therefore, saturated long-chain (>20 carbon atoms) FAs, which are biosynthesised exclusively by higher plants and are more stable than the more commonly used short-chain FAs, should be used. Third, given that FA concentrations can vary largely between sources, concentration-dependent SIMMs that are also able to incorporate δ13C-FA variability should be standard operation procedures to correctly assess the contribution of sediment sources via SIMMs. This paper reflects on the use of δ13C-FAs in erosion studies and provides recommendations for its application. We strongly advise the use of saturated long-chain (>20 carbon atoms) FAs as tracers and concentration-dependent Bayesian SIMMs. We anticipate progress in CSSI sediment fingerprinting from two current developments: (i) development of hierarchical Bayesian SIMMs to better address catchment complexity and (ii) incorporation of dual isotope approaches (δ 13C- and δ 2H-FA) to improve estimates of sediment sources.

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.

The Indian Ocean tsunami of December 2004 had far reaching consequences for agriculture in Aceh province, Indonesia, and particularly in Aceh Barat district, 150 km from the seaquake epicentre. In this study, the spatial distribution and temporal dynamics of soil and groundwater salinity and their impact on tree crops were monitored in Aceh Barat from 2006 to 2008. On 48 sampling points along ten transects, covering 40 km of coastline, soil and groundwater salinity were measured and related to mortality and yield depression of the locally most important tree crops. Given a yearly rainfall of over 3000 mm, initial groundwater salinity declined rapidly from over 10 to less than 2 mS cm−1 within two years. On the other hand, seasonal dynamics of the groundwater table in combination with intrusion of saline water into the groundwater body led to recurring elevated salinity, sufficient to affect crops. Tree mortality and yield depression in the flooded area varied considerably between tree species. Damage to coconut (65% trees damaged) was related to tsunami run-up height, while rubber (50% trees damaged) was mainly affected by groundwater salinity. Coconut yields (−35% in average) were constrained by groundwater Ca2+ and Mg2+, while rubber yields (−65% on average) were related to groundwater chloride, pH and soil sodium. These findings have implications on planting deep-rooted tree crops as growth will be constrained by ongoing oscillations of the groundwater table and salinity.

This paper summarizes key findings and identifies the main lessons learnt from a 5-year (2002-2008) coordinated research project (CRP) on "Assessing the effectiveness of soil conservation measures for sustainable watershed management and crop production using fallout radionuclides" (D1.50.08), organized and funded by the International Atomic Energy Agency through the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture. The project brought together nineteen participants, from Australia, Austria, Brazil, Canada, Chile, China, Japan, Morocco, Pakistan, Poland, Romania, Russian Federation, Turkey, United Kingdom, United States of America and Vietnam, involved in the use of nuclear techniques and, more particularly, fallout radionuclides (FRN) to assess the relative impacts of different soil conservation measures on soil erosion and land productivity. The overall objective of the CRP was to develop improved land use and management strategies for sustainable watershed management through effective soil erosion control practices, by the use of 137Cs (half-life of 30.2 years), 210Pb ex (half-life of 22.3 years) and 7Be (half-life of 53.4 days) for measuring soil erosion over several spatial and temporal scales. The environmental conditions under which the different research teams applied the tools based on the use of fallout radionuclides varied considerably - a variety of climates, soils, topographies and land uses. Nevertheless, the achievements of the CRP, as reflected in this overview paper, demonstrate that fallout radionuclide-based techniques are powerful tools to assess soil erosion/deposition at several spatial and temporal scales in a wide range of environments, and offer potential to monitor soil quality. The success of the CRP has stimulated an interest in many IAEA Member States in the use of these methodologies to identify factors and practices that can enhance sustainable agriculture and minimize land degradation. © 2012 Elsevier Ltd.

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 a tsunami event human casualties and infrastructure damage are determined predominantly by seaquake intensity and offshore properties. On land, wave energy is attenuated by gravitation (elevation) and friction (land cover). Tree belts have been promoted as “bioshields” against wave impact. However, given the lack of quantitative evidence of their performance in such extreme events, tree belts have been criticized for creating a false sense of security. This study used 180 transects perpendicular to over 100 km on the west coast of Aceh, Indonesia to analyze the influence of coastal vegetation, particularly cultivated trees, on the impact of the 2004 tsunami. Satellite imagery; land cover maps; land use characteristics; stem diameter, height, and planting density; and a literature review were used to develop a land cover roughness coefficient accounting for the resistance offered by different land uses to the wave advance. Applying a spatial generalized linear mixed model, we found that while distance to coast was the dominant determinant of impact (casualties and infrastructure damage), the existing coastal vegetation in front of settlements also significantly reduced casualties by an average of 5%. In contrast, dense vegetation behind villages endangered human lives and increased structural damage. Debris carried by the backwash may have contributed to these dissimilar effects of land cover. For sustainable and effective coastal risk management, location of settlements is essential, while the protective potential of coastal vegetation, as determined by its spatial arrangement, should be regarded as an important livelihood provider rather than just as a bioshield.

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.

SUMMARYIntegrated crop-livestock farming in the Guinea savanna of West Africa is often assumed to lead to synergies between crop and livestock production, thereby improving the overall productivity and resilience of agricultural production. Whether these synergies actually occur remains poorly studied. On-farm trials were conducted in northern Nigeria over a period of four years to assess the agronomic and economic performance of maize-legume systems with and without the integration of livestock (goats). Groundnut-maize rotations with livestock achieved the highest carry-over of nutrients as manure from one season to the next, covering approximately one-third of the expected N, P and K uptake by maize and reducing the demand for synthetic fertilizers. However, the advantage of lower fertilizer costs in rotations with livestock was offset by higher labour costs for manure application and slightly lower values of maize grain. Overall, no clear agronomic or economic benefits for crop production were observed from the combined application of manure and synthetic fertilizer over the application of synthetic fertilizer only, probably because the amounts of manure applied were relatively small. Legume-maize rotations achieved higher cereal yields, a better response to labour and fertilizer inputs, and a higher profitability than maize-based systems with no or only a small legume component, irrespective of the presence of livestock. Livestock at or near the farm could nevertheless make legume cultivation economically more attractive by increasing the value of legume haulms. The results suggested that factors other than crop benefits, e.g. livestock providing tangible and non-tangible benefits and opportunities for animal traction, could be important drivers for the ongoing integration of crop and livestock production in the savanna.

Nutrient balances are useful tools as indicators of potential land degradation and for optimizing nutrient use, and are thus highly relevant in the African context. A comprehensive literature review on nutrient balances in Africa was carried out to illustrate the main approaches, challenges, and progress, with emphasis on issues of scale. The review showed nutrient balances being widely used across the continent. The collected dataset from 57 peer-reviewed studies indicated, however, that most of the balances were calculated at plot and farm scale, and generated in East Africa. Data confirmed the expected trend of negative balances in the continent for nitrogen and potassium, where >75% of selected studies had mean values below zero. For phosphorus only 56% of studies showed negative mean balances. Several cases with positive nutrient balances indicated that soil nutrient mining cannot be generalized across the continent. Land use systems of wealthier farmers mostly presented higher nitrogen and phosphorus balances than systems of poorer farmers ( p p p

Three smallholder villages located in typical communal (from 1948), old (1987) and new (2002) resettlement areas, on loamy sand, sandy loam and clay soils, respectively, were selected to explore differences on natural resource management and land productivity. Focus group discussions and surveys were carried out with farmers. Additionally, farmers in three wealth classes per village were chosen for a detailed assessment of their main production systems. Maize grain yields (t ha−1) in the communal (1·5–4·0) and new resettlement areas (1·9–4·3) were similar but significantly higher than in the old resettlement area (0·9–2·7), despite lower soil quality in the communal area. Nutrient input use was the main factor controlling maize productivity in the three areas (R2 = 59–83%), while soil quality accounted for up to 12%. Partial N balances (kg ha−1 yr−1) were significantly lower in the new resettlement (−9·1 to +14·3) and old resettlement (+7·4 to +9·6) than in the communal area (+2·1 to +59·6) due to lower nutrient applications. Averaged P balances were usually negative. Consistently, maize yields, nutrient applications and partial N balances were higher in the high wealth class than in poorer classes. This study found that most farmers in the new resettlement area were exploiting the inherent soil nutrient stocks more than farmers in the other two areas. We argue that effective policies supporting an efficient fertilizer distribution and improved soil management practices, with clearer rights to land, are necessary to avoid future land degradation and to improve food security in Zimbabwe, particularly in the resettlement areas. Copyright © 2009 John Wiley & Sons, Ltd.

Slow establishment of green barriers together with competition for nutrients and water between crops and contour hedges hamper their acceptance by rural communities in tropical mountainous regions. Alternatively, a combination of hedges/barriers and minimum tillage may shift the pathway of N losses from water erosion towards leaching. In Northeast Thailand, run-off, soil loss, N leaching (by resin cores) and crop response were monitored in grass barriers (Vetiveria zizanioides, Brachiaria ruziziensis) and hedgerow (Leucaena leucocephala) based soil conservation systems in fertilized/unfertilized treatments from their establishment in 2003 to 2005. In all treatments, maize was grown on a moderate slope gradient (21–28%) under minimum tillage conditions and relay cropped with a legume cover crop (Canavalia ensiformis). After 3 years, maize grain yields increased from 1.5 and 3.2 to 3.8 and 5.5 Mg ha−1 in the unfertilized and fertilized control plots. Over the same period, yield increases were lower for soil conservation treatments reaching yields of 2.0–2.7 Mg ha−1 without fertilizer and 3.9–4.2 Mg ha−1 with fertilizer. After 3 years, runoff (190–264 m3 ha−1) and soil loss (0.2–1 Mg ha−1) in fertilized plots with barriers showed an average decrease of 72% and 98%, respectively, compared to 2003, the reduction being lower in unfertilized plots. The control had a much higher soil loss in the first year (24.5 Mg ha−1), but also showed much reduced erosion (1.6–2.5 Mg ha−1) in the third year, partly due to reduced rainfall but also due to the combined effects of minimum tillage and surface mulch. Runoff, however, did not decrease on the control plots over the years in the same way as it did under soil conservation (runoff only after >12 mm day−1). Average cumulative N losses by runoff, soil loss and leaching were reduced from 55 kg N ha−1 in the control to 37–40 kg N ha−1 in the barrier treatments. The dominant N loss pathway shifted from above ground N losses to leaching with the establishment of barriers and hedges. Due to the positive maize yield development and partial control of soil loss, minimum tillage combined with legume relay cropping under the trial conditions indicates a potential alternative to contour barrier/hedgerow systems for soil conservation on moderate slopes in tropical mountainous regions.

Competition for nutrients and water between crops and associated hedgerows reduces overall performance of contour hedgerow systems and hampers its acceptance by rural communities in tropical mountainous regions. Therefore, it is imperative to better understand competition leading to a decline in crop response close to hedges. In the highlands of North East Thailand spatial variability in grain yield of maize (Zea mays L., cv. Suwan 1) was assessed for two contour hedgerow systems based on Brachiaria ruziziensis Germain et Evrard (Ruzi grass) barriers or Leucaena leucocephala (Lam) de Wit hedges without or with fertilizer (60 kg N ha−1 and 14 kg P ha−1). Available % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX% garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz% aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq% Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq% Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca% WGobGaam4tamaaDaaaleaacaaIZaaabaGaeyOeI0caaOGaeyOeI0Ia% amOtaaaa!3CD8! $$NO^{ - }_{3} - N$$ was analyzed across the slope. In addition, shoot N concentration and δ13C values in leaves were measured for maize plants in the center of the alley and in the row next to and at the upper side of barriers or hedges. Despite variable field conditions, δ13C values were significantly (p

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 relationships between 13C isotopic discrimination and water stress are well documented for C3 and C4 plants. However, the application in the field is hampered by complex interaction patterns with other common stress factors, such as nutrient deficiency. In addition, questions arise if temporal reductions in water availability during crop growth can be traced back using δ13C data in the field. The objective of this study therefore is to assess the potential use of δ13C observations to quantify water stress and its dynamics in maize (Zea mays L.) grown under low to high nitrogen availability, and to develop tools based on δ13C values for its diagnosis in the field. In a pot experiment, carried out in a screen house in Ibadan, Nigeria, we grew maize for 60 days under four watering regimes, (i) optimum (at field capacity) during 60 days, (ii) optimum from 0 to 30 days and stressed (50% field capacity) from 30 to 60 days, (iii) stressed from 0 to 30 days and optimum from 30 to 60 days, and (iv) stressed throughout the 60 days. Nitrogen was applied at three rates (none, moderate (45 kg N ha−1) and high (120 kg N ha−1)). Plants were sampled after 30 and 60 days. At 60 days, leaves developed during the first 30 days were sampled separately from those developed between 30 and 60 days. Shoot production showed a clear water–nitrogen interaction. Nitrogen response increased with decreasing water stress, in particular from 30 to 60 days. δ13C values ranged from −12.42‰ to −10.80‰. Overall, a clear and significant water and nitrogen effect (P

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.

The drainage basin of the Deleg River (88 km(2)), located in the southern Ecuadorian Andes, was studied to assess the geomorphic and hydrologic response of a fluvial system to human-induced environmental change in its contributing area. Historical data on land use, channel morphology and sedimentology were collected, based on a spatial analysis of aerial photographs (1963-1995) and a field survey (2002). Analysis of channel cross-sectional profiles and sedimentological data revealed a major change in morphology and sedimentology of the Deleg River during the past four decades: (i) the active river channel narrowed by over 45%, (ii) the riverbed incised on average by over 1.0 m and (iii) the median grain size of the bed surface decreased from 13.2 cm to 4.7 cm. The spatial pattern of land cover within the Deleg catchment also changed considerably: highly degraded agricultural land in the low-lying areas was abandoned and partially afforested for timber and wood production, whereas secondary upland forest was increasingly cleared for expansion of cropland and pastures. Notwithstanding large changes in the spatial organization of land use within the catchment, the overall land use did not change significantly during the past four decades. This suggests that the response of the Deleg River to land-use change not only depends on the overall land-use change, but also on the spatial pattern of land-use/cover change within the catchment. Although forestation and regeneration of bare gully slopes and floors throughout the catchment only represented a minor part of the total land-use change, these land-use/cover changes had a major impact on the hydrological and sediment connectivity in the landscape. (c) 2005 Elsevier B.V. All rights reserved.

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.

Drawing on qualitative data from a longitudinal case study of a collaborative soil conservation initiative in southern Ecuador, we study how multiple actors, including university experts, development organizations and local communities, make sense of the issues from different perspectives through the process of issue framing. Starting from an analysis of the actors’ usual issue frames, we point out their differences in selecting aspects, connecting them and drawing boundaries around the issues. Bringing in the time dimension leads us to consider how changing patterns of actor involvement and evolving frame configurations mutually influence each other. In a third step, we zoom in on the here-and-now level of ongoing interaction using discourse analysis, outlining an interactive, communicative and discursive approach to dealing with differences in issue framing. We identify various ways of dealing with these differences and argue that approaching them constructively by tuning the different frames into a mutually acceptable configuration is an important challenge for any attempt at integrated management of natural resources. Copyright # 2004 John Wiley & Sons, Ltd.

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

Aerial photographs taken in 1976 and 1989 and a field survey in 1999 showed that land use in a 900-ha catchment in the southern part of the Ecuadorian Andes is highly dynamic. Over 23 years, ca. 83 ha of arable land was abandoned and ca. 70 ha was taken into agricultural production. Changes in land use were not spatially homogeneous. Parcels on unstable geologic formations and close to village centres were preferably set-aside. Land taken into cultivation was preferably located on gently sloping areas close to newly built sites and arterial roads. The area with bush vegetation increased by regeneration of natural vegetation on fields set-aside in the late 1970s and early 1980s. There was a complex interaction between water erosion and environmental change in the study area. Land taken into production was levelled for furrow irrigation: this led to a net reduction in the area susceptible to water erosion. However, one quarter of the area affected only by sheet and rill erosion 23 years ago has since become incised by deep gullies. This increase in gully density was related to inadequate construction and management of irrigation infrastructure, rather than to change in vegetation cover and/or soil erodibility caused by agricultural practices. This factor is often overlooked in studies of the effects of environmental change on geomorphologic processes. (C) 2002 Elsevier Science B.V. All rights reserved.

The demand to improve soil health, arrest land degradation, in particular desertification in agro-ecosystems and protect land and water resources for food production and sustainable agricultural and socio-economic development is expected to increase in the next 50 years as a result of the continuing worldwide population growth and the increased reliance on limited natural resource-based economy. Moreover, the intensive competition for land and water resources from industrial, urban and other sectors and the impacts of widespread soil degradation and global climate change will place increasing pressure on the need to improve sustainable land and water use and management. The objective of the Soil and Water Management & Crop Nutrition (SWMCN) Subprogramme of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture is to assist Member States to use isotopic and nuclear-based techniques to diagnose constraints and pilot-test interventions to intensify crop production in a sustainable manner through the integrated management of soil, water and nutrient resources without land degradation. This objective is pursued through a range of activities including (a) co-ordinated research projects (CRP) which involve international networks of national agricultural research organizations from developing countries, advanced research institutes and CGIAR institutions, and (b) technical co-operation projects (TCP) that promote technology transfer through technical support and institutional capacity building in FAO and IAEA Member States. This chapter will report on the application of isotopic and nuclear techniques to unravel processes and factors that affect land degradation and major findings obtained from both CRPs and TCPs that were aimed to avoid and mitigate land degradation. Since land degradation includes not only soil erosion but also the decline in soil quality and their constituents (such as water and nutrients) with its subsequent reduction in crop production, projects that are associated with improving soil health, minimizing nutrient mining, combating soil salinity, soil acidity and desertification and enhancing water use efficiency will also be briefly presented and discussed.

Based on experimental evidence that combining mineral fertilizers with organic matter may address poor soil fertility status and result in added benefits, farmer-managed demonstration trials were initiated in 9 villages in the northern Guinea savanna (NGS) of northern Nigeria. The trials had four treatments: (i) a farmers control in which the farmer grows maize according to his usual practice, (ii) the maize technology being promoted by the NGO Sasakawa-Global2000 (SG2000), involving hybrid seeds, proper plant density and fertilizer application practice, and fertilizer application rates that are relatively high for the region (136 kg N, 20 kg P, and 37 kg K ha-1), (iii) the Balanced Nutrient Management Systems (BNMS) manure technology that follows the SG2000 package for maize, except that part of the fertilizer quantity is replaced by animal manure; and (iv) a soybean-maize rotation, again with reduced fertilizer rate to the maize.

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.

During the last decades, there is a boom of the use of aerial photographs and remote sensing images to collect quickly accurate digital information in remote areas. Due to an easier accessibility of aerial photographs and a significant decrease of their price as well as that of the image analysis and GIS software, these techniques are becoming increasingly popular. This article presents a methodology to use Geographic Information Systems for quantifying past land use changes from aerial photographs. An application of this technique to the Austro Ecuatoriano has demonstrated that such a methodology requires that the data are both spatially and temporally compatible. In order to obtain spatially compatible data, the air photos are geo-referenced using a set of ground control points (GCP's). Our analysis shows that, if certain conditions are satisfied, GCP's obtained from topographical maps are of sufficient quality to carry out the geo-referencing procedure with a very good precision. On the other hand, temporal compatibility appears more difficult to achieve : the scale (and probably the quality) of the air photos has a significant effect on the resulting land use classification. Consequently, a calibration of the various datasources is necessary in order to avoid bias in the final results., Resume : Utilisation de photographies aériennes séquentielles pour détecter les changements d'utilisation du sol dans l'Austro Equateur. Durant les dernières décennies, il y a eu un accroissement de l'utilisation des photographies aériennes et de l'imagerie satellitaire pour récolter rapidement de l'information digitale dans un certain nombre de régions. Du fait d'une accessibilité plus grande des photographies aériennes et d'une décroissance significative de leur coût, aussi bien pour les logiciels de traitement d'image et de l'information géographique, ces techniques ont connu une popularité croissante. Cet article présente une méthodologie pour utiliser des Systèmes d'Information Géographiques pour quantifier les changements d'usages du sol passés à partir de photographies aériennes. Une application de cette technique à l'Austro Equateur a montré qu'une telle méthodologie nécessitait une compatibilité des données à la fois spatiales et temporelles. Pour obtenir des données spatialement compatibles, les photographies aériennes sont géoréférencées sur la base de l'utilisation d'une série de points de contrôle de base. Notre analyse montre que, si certaines conditions sont satisfaites, ces points de contrôle obtenus à partir de cartes topographiques sont suffisants en qualité pour exécuter une procédure de géoréférencement avec une très bonne précision. D'autre part, la compatibilité temporelle apparaît plus difficile à mettre en œuvre : l'échelle (et probablement la qualité) des photographies aériennes a un effet significatif sur la classification de l'utilisation du sol qui en découle. Par conséquent, un étalonnage des différentes sources de données est nécessaire de façon à éviter des erreurs dans les résultats., Vanacker Veerle, Govers Gérard, Tacuri Eduardo, Poesen Jean, Dercon Gerd, Cisneros Felipe. Using sequential aerial photographs to detect land-use changes in the Austro Ecuatoriano / Utilisation de photographies aériennes séquentielles pour détecter les changements d'utilisation du sol dans l'Austro Equateur. In: Revue de géographie alpine, tome 88, n°3, 2000. pp. 65-75.