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[en] In the previous Soils Newsletter (Vol 31, No. 2, January 2009) we presented the preliminary results in evaluating 137Cs fallout in an undisturbed Slovenian forested site prior to future erosion and sedimentation investigation. As the greatest part of the external irradiation comes from the main naturally occurring radionuclides, we studied the natural gamma geogenic background. Laboratory analytical measurement precision concerning the following isotopes: 40K, 226R and 232Th (terrestrial radionuclides used to evaluate the natural gamma dose ray). Result of the Minimum Detectable Activity (MDA) is based on a 50 000s γ-analysis of 20 different core samples collected till 40 cm per 10 cm increments (total of 80 samples).
[en] The speaker will discuss the principles and applications of Mid-Infrared Spectroscopy, in particular Diffuse-Reflectance Infrared Fourier-Transformed (DRIFT) Spectroscopy, important to many fields of soil and plant sciences. The applications will encompass those utilized for the analysis of soil and plant properties in a broad spectrum of fields including the assessment of spatial variability in soil properties within soil profiles (Vancampenhout et al., 2008) and soil quality at landscape level (Cobo et al., 2008; Schmitter et al., 2009), soil organic chemistry as a proxy for climate and vegetation in paleosols (Vancampenhout et al., 2008) and plant quality characterization (Kuehnle et al., 2008). Infrared spectroscopy is based on the principle that molecules have specific frequencies at which they rotate or vibrate corresponding to discrete energy levels .In practical terms, this means that light energy in the mid infrared range (4000 to 500 cm-1) is focused onto the soil sample. Part of this light is absorbed and the remaining light is reflected back into the spectrometer and analysed. The resulting spectrum presents the nature of the sample. The precise properties of the sample can be predicted using Partial Least Squares (PLS) statistical analysis, once the equipment has been calibrated. Due to advances in spectrometer capacity and spectral data processing techniques, infrared spectroscopy has been widely used in characterizing the properties of soil samples, such as soil organic matter content and its fractions, cations, total nitrogen, clay minerals, and carbonates. However, prediction at present is limited to those properties that are in equilibrium with the soil particles (CSIRO, 2009). Extractable nitrate, phosphorus, sulfur and micronutrients cannot yet be precisely assessed, as these occur in the soil solution around and between soil particles. Since 1993, DRIFT spectroscopy is rapidly gaining field in the study of soils and soil organic material since it is fast, accurate, cost effective and can be used without major sample preparation. Because of the low costs of the analyses, it is of particular interest for applications in landscape variability surveys and precision agriculture (need for high spatial density of the sampling locations). (author)
[en] The IAEA technical cooperation project MAG5015 'Optimization of phosphate fertilization of Ferralsols in the Highland Areas of Madagascar' was initiated in 2004 with the objective to enhance food security of small landholders in the 'Tanety' (upland in Malagasy) areas of Madagascar by increasing crop productivity through appropriate management of soil and nutrients inputs in rainfed cropping systems and to build national capacity in the use of nuclear and related techniques. The project focuses mainly on the improvement of P availability in Malagasy cropping systems through a better understanding of the phosphorus cycle in the soil
[en] Full text: A new weather station (iMETOS ag station from Pessl Instruments) was setup and installed in the Seibersdorf field experimental station. The weather station records temperature, relative humidity, dew point temperature, leaf wetness, rainfall, global radiation and wind speed. These data will be compared with an existing weather station installed nearly twenty years ago. The iMetos was also expanded to include soil moisture sensors and soil matric potential sensor (Decagon 10HS and MPS-1, respectively). The latter will also be used as part of the comparison of different soil moisture monitoring sensors (TDR, EnviroScan, Neutron Probe and Diviner) available in the field. The whole weather station and soil moisture sensor setup will be useful in providing evapotranspiration data and irrigation scheduling for the field experiment on 'Integrating soil water measurements and isotope tracer (13C, 18O and 2H) techniques to evaluate wheat lines for tolerance to drought under pre- and post-anthesis water stress'. The study aims to relate soil water measurements with isotopic signatures of carbon and oxygen in plant leaves to select wheat lines tolerance to water stress at different growth stages and to compare the reliability of the different soil water monitoring equipments to estimate plant available water for wheat plants grown under different water stressed conditions plus to provide quantitative information on the use of isotope tracer techniques to evaluate wheat plants for tolerance to water stress at the different growth stages. The weather and soil data also will be useful for fellowship training in soil moisture instrumentation and soil water balance. The iMetos is powered by rechargeable batteries and a solar panel. It is a wireless internet based data-logging system which makes it convenient to view or download the data anywhere, anytime
[en] There is an increasing concern for maximizing the efficiency of fertilizer nitrogen (N) use in crop production systems and the 15N techniques have been used extensively to study the uptake of applied N by plants and the nitrate concentration in soils at different depths. The 15N labeling method, the isotopic signature of the enriched tracer can be pre-determined to ensure significant difference in atom % of 15N between source and background level, even when fractionation occurs. This technique has been used extensively to trace fate of soil nitrate in cropping systems
[en] In this Newsletter, one will see several developments in the Soil and Water Management and Crop Nutrition Section Subprogramme which provide information and technical support to Member States in the areas of land and water management for sustainable agriculture
[en] Improving food security, environmental preservation and enhancing livelihood should be the main targets of the innovators of today's farming systems. Conservation agriculture (CA), based on minimum tillage, crop residue retention and crop rotations, has been proposed as an alternative system combining benefits for the farmer with advantages for the society. This paper reviews the potential impact of CA on C sequestration by synthesizing the knowledge of carbon and nitrogen cycling in agriculture, summarizing the influence of tillage, residue management and crop rotation on soil organic carbon stocks and compiling the existing case study information. To evaluate the C sequestration capacity of farming practices, their influence on emissions from farming activities should be considered together with their influence on soil C stocks. The largest contribution of CA to reducing emissions from farming activities is made by the reduction of tillage operations. The soil C case study results are not conclusive. In 7 of the 78 cases withheld, the soil C stock was lower in zero compared to conventional tillage, in 40 cases it was higher and in 31 of the cases there was no significant difference. The mechanisms that govern the balance between increased or no sequestration after conversion to zero tillage are not clear, although some factors that play a role can be distinguished e.g. root development and rhizodeposits, baseline soil C content, bulk density and porosity, climate, landscape position and erosion/deposition history. Altering crop rotation can influence soil C stocks by changing quantity and quality of organic matter input. More research is needed, especially in the tropical areas where good quantitative information is lacking. However, even if C sequestration is questionable in some areas and cropping systems, CA remains an important technology that improves soil processes, controls soil erosion and reduces tillage-related production costs. (author)
[en] A joint review paper was produced at the final stage of the CRP D1.50.08 by the participants and supporting the implementation of the IAEA SWMCN subprogramme aims to review the advantages and limitations of each of the three FRNs (137Cs, 210Pbex and 7Be) and to identify key knowledge gaps linked to their use. In addition, guidelines for selecting the most appropriate FRN and associated approach, in order to deal with a range of spatial and temporal scales and to investigate specific sets of agro-environmental problems, were provided. Key requirements for future work in Member States, related to the application of FRNs in soil erosion investigations, were also identified. These include the upscaling of the approach to the catchment scale and a shift from use of the approach as a research tool to a decision support tool. To summarise, the selection and application of a particular FRN for documenting or investigating soil erosion and redistribution should reflect the user's objectives, the advantages and limitations of each approach, and the human and material resources available
[en] Full text: Agriculture is under increasing pressure to deliver maximum productivity and meet food security whilst also delivering environmental protection/benefits through responsible land and water management. Poor water management in particular has the potential to cause erosion, eutrophication, groundwater contamination, secondary salinisation and wastage of precious water resources. There are numerous tools for assessing water use management in agriculture, viticulture and horticulture. Plant-focused tools have an advantage in that they can identify exactly what the crop/tree is doing in among all the various other factors such as evaporation, drainage and runoff. By contrast, soil or atmospheric measurements require careful analysis to disentangle the effects of aggregated processes. That is not to say plant-based techniques are without their challenges and disadvantages. Perhaps the most powerful tool at our disposal is thermometric xylem flux measurement. Here we use heat as a tracer to determine the flow of water inside the plant tissues. Usually installed at the base of the plant, these devices are wrapped around, or implanted (as thin needles) into, the stem. Small amounts of heat are applied and then monitored with temperature sensors using a range of algorithms to calculate flow rate. A strong knowledge of plant vascular architecture, experimental design, and mathematical principles is a vital contributor to the use of these deceptively simple devices. A growingly popular algorithm called the heat ratio method (HRM) is particularly sensitive to fine-scale flow dynamics and is good for measuring flows even in drought conditions, at night, or other low water use times where other systems fail. Sap flow measurements can be use to analyse the effects of rain pulses, irrigation events, soil water deficit etc. Because they provide real-time readings every 10-30 minutes throughout the year, water flow behaviours can be given close scrutiny to help schedule irrigation for a range of conditions. Modern telemetric links can deliver the data to the desktop of the farm manager on demand. Although skill of interpretation is required, there is a wealth of information on plant water use dynamics hidden in each daily trace, in the same way a heart-monitor trace provides health information to a doctor. Sap flow devices such as HRM can be combined powerfully with other techniques such as neutron moisture meters, soil isotopic measurements, etc. to improve understanding of transpiration and evaporation in the soil-plant system. Sap flow training activities in SWMCN In April, as part of Stephen Burgess's work as consultant with the Soil and Water Management and Crop Nutrition Section, he provided in-depth theory-based lectures and practical demonstrations to Soil Science Unit staff and fellows from Bangladesh, Mali, Kenya, Eritrea and Zimbabwe on the use of thermometric techniques to measure xylem sap flow in intact plants. Focusing chiefly on the HRM method which Mr Burgess himself developed in 1996, participants were given insights and ideas on how and why this type of technique might be useful in their research activities.
[en] Full text: The aim of this study performed in 2006-2008 by the Soil Science Unit in collaboration with Boku University in Mistelbach watershed (Austria) was to evaluate the magnitude of deposition rates using 137Cs and 210Pbex and the erosion rates using runoff plot measurements. The final results published recently in the peer-reviewed journal Geoderma can be summarised as following: (i) Erosion measurements (1994-2006) from runoff plots located in the upper part of an agricultural field just up-slope from a deposition area reached 29.4 t ha-1 · a-1 from the conventional tilled plot, 4.2 t ha-1 · a-1 from the conservation tillage plot and 2.7 t ha-1 · a-1 from the direct seeding treatment. Soil losses were reduced significantly by a factor of 10 using no tillage, direct seeding treatment. (ii) Using the 137Cs data that integrate the 1954-2007 period, the sedimentation rates down slope of the field containing the runoff plots were estimated at: - 26.1 t-1 · ha-1 · ha-1 using the 137Cs depth distribution profile - 20.3 t-1 · ha-1 · a-1 using the Mass Balance Model 2 (MBM2). (iii) The erosion rates under conventional tillage are in agreement with the sedimentation rates estimated down slope of the field by the 137Cs depth distribution profile and MBM2. (iv) In the lowest part of the watershed a sedimentation rate of 50.5 t-1 · ha-1 · a-1 was highlighted by the 137Cs depth distribution profile. This value was greater than the average erosion rate measured by the erosion plots because this area is more representative of sedimentation processes occurring in the study area due to its topographical position and the basin geomorphology. While 137Cs produced exploitable results, the 210Pb method was not applicable due to very low concentrations of 210Pbex associated to a high uncertainty in the measurements and a high fallout variability