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Arresting land degradation, not to mention remediation, requires long-term investment. Budgetary constraints mean that we have to prioritise, so decision makers need know exactly where and how severe is the degradation, and they need early warning to act in good time. The first global assessment using actual measurements was based on 23 years of Advanced Very High Resolution Radiometer (AVHRR) Normalised Difference Vegetation Index (NDVI) data at 8km resolution. Its aim was to identify black spots that should be investigated in the field – but hardly anybody did. The dataset now extends to 33 years, revealing both long-term trends and many reversals of trend. The areas hardest hit are sub-equatorial Africa, with outliers in the Ethiopian highlands and the Sahel; the Gran Chaco, Pampas and Patagonia; southeast Asia; the steppes from Moldova eastwards into Central Asia; the Russian far east and northeast China; and swaths of high-latitude forest. Since 2000, it has been possible to seamlessly scale up the coarse-resolution picture to 250m resolution using data from the Moderate- Resolution Imaging Spectroradiometer (MODIS) and to 30m resolution with Landsat. Now, thanks to commercial satellite data, we can zoom in, anywhere in the world, with 5m-resolution.

We set out to map the soil organic carbon (SOC) content, as an indicator of soil fertility, at the village scale, and to relate the SOC content to farm scale management and landscape scale characteristics. Topsoil samples were taken at 100 random locations in the Murewa smallholder farming area in Zimbabwe and analysed for organic carbon. Using digital soil mapping techniques and Landsat TM images we could explain 50% of the observed SOC variance. The average SOC content was estimated to be 1.5%, although the sandy cropping area had a much lower average of 0.8% and the red clays and valleys had higher average of 1.8%. The SOC variability could not be linked to farm management. No fertility gradients were observed, mostly due to a strong dominance of clay content on the spatial distribution of SOC. Clay content was able to explain 57% of the SOC variance, while farm area and labour size, typically used for farmer typology, were able to explain only an additional minor part of the SOC variance. This strong landscape scale effect needs to be included in future village-scale studies. We conclude that digital soil mapping of soil fertility gradients at the village scale has several scale issues that need to be addressed if the envisioned global digital soil map is to be relevant for smallholder farmers in sub-Saharan Africa.

Food production, water availability and energy production are important ecosystem services of the Upper Tana basin (Kenya) and they decline due to upstream erosion affecting downstream water users. The effect of 11 soil conservation measures on soil erosion and the three ecosystem services was estimated by a modelling approach to assess agro-ecological processes and benefit/cost relations. Soil water available for evaporation and transpiration (‘green water’) functioned as a unifying concept to express the effects of erosion and the impacts of soil and water conservation measures that result in: (1) increased water availability for crops; (2) increased fluxes towards aquifers, thereby increasing water supply and regulating streamflow, and (3) a reduction of erosion and siltation of reservoirs used for hydroelectricity. Modelling indicated that the three ecosystem services could be improved, as compared with the base level, by up to 20% by introducing appropriate conservation measures with benefit/cost relations of around 7. However, farmers were unable to make the necessary investments and much effort and many institutional studies were needed to achieve progress towards implementation by initiating the Green Water Credits (GWC) programme intended to arrange payments by downstream businesses to upstream farmers. A timeline analysis is presented to illustrate the slow, but persistent, development of transdisciplinary activities as a function of time using connected value development as a guiding principle.

Much knowledge is available on soil threats in Europe, but this is fragmented and incomplete, in particular regarding the complexity and functioning of soil systems and their interaction with human activities. The main aim of the new RECARE project is to develop effective prevention, remediation and restoration (or Sustainable Land management – SLM) measures using an innovative trans-disciplinary approach in 17 case study areas across Europe, covering a range of soil threats in different bio-physical and socio-economic environments. Within these Case Study sites, i) the current state of degradation and conservation will be assessed ii) impacts of degradation and conservation on soil functions and ecosystem services will be quantified, iii) SLM measures will be selected, implemented and evaluated in a participatory process, and iv) the applicability and impact of these measures at the European level will be assessed. Existing national and EU policies will be reviewed and compared to identify potential contradictions and synergies. A comprehensive dissemination and communication strategy will serve a variety of stakeholders to stimulate renewed care for European soils

Soil information system in SOTER (soil and terrain digital database) framework is developed for the Indo-Gangetic Plains (IGP) and black soil regions (BSR) of India with the help of information from 842 georeferenced soil profiles including morphological, physical and chemical properties of soils in addition to the site characteristics and climatic information. The database has information from 82 climatic stations that can be linked with the other datasets. The information from this organized database can be easily retrieved for use and is compatible with the global database. The database can be updated with recent and relevant data as and when they are available. The database has many applications such as inputs for refinement of agro-ecological regions and sub-regions, studies on carbon sequestration, land evaluation and land (crop) planning, soil erosion, soil quality, carbon and crop modelling and other climate change related research. This warehouse of information in a structured framework can be used as a data bank for posterity.

Large areas in the Upper Tana river catchment, Kenya, have been over-exploited, resulting in soil erosion, nutrient depletion and loss of soil organic matter (SOM). This study focuses on sections of the catchment earmarked as being most promising for implementing Green Water Credits, an incentive mechanism to help farmers invest in land and soil management activities that affect all fresh water resources at source. Such management practices can also help restore SOM levels towards their natural level. Opportunities to increase soil organic carbon (SOC) stocks, for two broadly defined land use types (croplands and plantation crops, with moderate input levels), are calculated using a simple empirical model, using three scenarios for the proportion of suitable land that may be treated with these practices (low¿=¿40¿per¿cent, medium¿=¿60¿per¿cent, high¿=¿80¿per¿cent). For the medium scenario, corresponding to implementation on ~348¿000¿ha in the basin, the eco-technologically possible SOC gains are estimated at 4·8 to 9·3¿×¿106¿tonnes (Mg) CO2 over the next 20¿years. Assuming a conservative price of US$10 per tonne CO2-equivalent on the carbon offset market, this would correspond to ~US$48–93 million over a 20-year period of sustained green water management. This would imply a projected (potential) payment of some US$7–13¿ha-1 to farmers annually; this sum would be in addition to incentives that are being put in place for implementing green water management practices and also in addition to the benefits that farmers would realize from the impact on production of these practices themselves

The outcomes of the discussion in the four working sessions showed that although there is an urgent need to improve soil carbon management and stocks, and despite the existing knowledge about good agricultural practices to achieve this goal, these are not put into practice effectively and globally. The apparent contradiction has to do with a mismatch of policies at different societal and geographical scales, and the low policy profile of SOC. All participants agreed in the need to bring SOC into the core of environmental policies at all levels and to improve the governance of policy actions by addressing the stakeholders in a more effective way. Fil: Banwart, Steven. University of Sheffield. Kroto Research Institute; Reino Unido Fil: Black, Helaina. James Hutton Institute; Reino Unido Fil: Cai, Zucong. Nanjing Normal University; China Fil: Gicheru, Patrick. Kenya Agricultural Research Institute; Kenia Fil: Joosten, Hans. University Greifswald; Alemania Fil: Victoria, Reynaldo. Universidade de Sao Paulo; Brasil Fil: Milne, Eleanor. State University Of Colorado Boulder; Estados Unidos Fil: Noellemeyer, Elke Johanna. Universidad Nacional de La Pampa. Facultad de Agronomía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Pascual, Unai. Basque Centre for Climate Change; España Fil: Nziguheba, Generose. Columbia University; Estados Unidos Fil: Vargas, Rodrigo. University of Delaware; Estados Unidos Fil: Bationo, Andre. International Fertilizer Development Center; Ghana Fil: Buschiazzo, Daniel Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina Fil: de Brogniez, Delphine. European Commission; Italia Fil: Melillo, Jerry. Ecosystems Centre of The Marine Biological Laboratory; Estados Unidos Fil: Richter, Dan. University of Duke; Estados Unidos Fil: Termansen, Mette. University Aarhus; Dinamarca Fil: van Noordwijk, Meine. International Centre for Research in Agroforestry; Indonesia Fil: Goverse, Tessa. United Nations Environment Programme. Division of Early Warning and Assessment; Kenia Fil: Ballabio, Cristiano. European Commission; Italia Fil: Bhattacharyya, Tapan. Indian Council of Agricultural Research. National Bureau of Soil Survey and Land Use Planning. Division of Soil Resource Studies; India Fil: Goldhaber, Marty. United States Geological Survey; Estados Unidos Fil: Nikolaidis, Nikolaos. Technical University of Crete; Grecia Fil: Zhao, Yongcun. Chinese Academy of Sciences; República de China Fil: Funk, Roger. Leibniz Centre for Agricultural Landscape Research. Institute for Soil Landscape Research; Alemania Fil: Duffy, Chris. State University of Pennsylvania; Estados Unidos Fil: Pan, Genxing. Nanjing Agricultural University; China Fil: la Scala, Newton. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Gottschalk, Pia. Potsdam Institute for Climate Impact Research; Alemania Fil: Batjes, Niels. International Soil Reference and Information Centre. World Soil Information; Bélgica Fil: Six, Johan. Eidgenössische Technische Hochschule Zürich; Suiza Fil: van Wesemael, Bas. Université Catholique de Louvain; Bélgica Fil: Stocking, Michael. University of East Anglia; Reino Unido Fil: Bampa, Francesca. Università di Padova; Italia Fil: Bernoux, Martial. French Research Institute for Development; Francia Fil: Feller, Christian. French Research Institute for Development; Francia Fil: Lemanceau, Philippe. Institut National de la Recherche Agronomique; Francia. University of Burgundy; Francia Fil: Montanarella, Luca. European Commission; Italia

The Netherlands has a long history of soil research. Over the past 150 years, seven national soil maps have been produced at scales ranging from 1:50,000 to 1:1,000,000. The maps were based on different conceptual models which reflected advances in soil science as well as societal demands. There are four phases in the development of soil mapping in The Netherlands. The first three are: (i) the geological phase (1837–1937), (ii) the physiographic phase (1937–1962) and (iii) the morphometric phase (1962–1995). The earliest soil maps, made in the mid-1800s, were largely based on surface geology. In 1950 the first national soil map was published based on physiographic soil mapping. From the 1960s onwards, mapping followed a pedogenetic–morphometric approach and these maps have been widely used in land use planning, hydrologic studies, re-allotments, and agricultural land evaluations. An increase in environmental awareness with the need to assess environmental impacts and developments in information technology induced the digital soil information phase (1995–present). New technologies have improved the collection, storage, analysis and presentation of soil geographic information. It is concluded that initial soil mapping in The Netherlands had a strong agricultural focus but that the current maps are used in a wide range of applications.

A relatively stable biomass productivity of perennial crop after plantation establishment makes it possible to calculate their total biomass yield through predicting the annual biomass yield. The generic model LINPAC (LINTUL model for Perennial and Annual Crops) is presented to predict annual biomass yield of energy crops on large spatial scales by adding new modules to LINTUL: (1) Leaf Area Index (LAI) is simulated independent of specific leaf area; (2) a species specific daily Light Use Efficiency (LUE, g MJ-1) is modified by temperature and light intensity; (3) crop base temperature is generated by local weather conditions within crop physiological ranges. LINPAC is driven either by site-specific input data or by globally gridded weather and soil data. LINPAC was calibrated on the basis of a model sensitivity analysis of the input parameters and validated against different agro-ecological experimental data sets for two grass species Miscanthus (Miscanthus spp.) and Reed canary grass (Phalaris arundinacea L.), and for two woody species Willow (Salix spp.) and Eucalyptus (Eucalyptus spp.). LINPAC reproduced the biomass yields with a normalized root mean square error (RMSE) of 17%, comparable to the coefficient of variation (CV = 12%) of the experimental data. In the model photosynthetic pathways were differentiated by assigning higher LUE values for the C4 crop (Miscanthus) compared with the C3 crops (others), leading to higher simulated biomass yield of Miscanthus (18.8 ± 1.5 t ha-1) over Reed canary grass (10.5 ± 1.6 t ha-1) in comparable environments. LINPAC is applicable for local, regional and global estimations of biomass yield of energy crops.

Crop residue mulching combined with zero tillage and crop rotation, known as conservation agriculture (CA), is being promoted as an alternative system to revert soil degradation in maize-based farming in the central highlands of Mexico. The goal of this paper was to determine the effects of CA vs. conventional tillage systems on soil quality, with a special focus on the role of earthworms in affecting the soil structure morphology, and on crop yield. For the conventional tillage system, the effect of crop residue retention (CONV + RES) was also compared to the conventional farmers’ practice (residues removed; CONV). CA resulted in four times higher earthworm abundance when compared to CONV. Residue retention per se (CONV + RES) did not favor earthworm abundance. In all cases the earthworm community was dominated by exotic species. CA increased total N and soil organic C concentrations relative to CONV, but only at 0–5 cm soil depth. Nevertheless, the more pronounced vertical stratification of soil organic carbon content under CA favored soil surface aggregation and aggregate stability as expressed by the aggregate mean weight diameter after dry sieving (MWDds = 2.6 mm for CA and 1.6 mm for CONV) and wet sieving (MWDws = 0.9 mm and 0.6 mm, respectively). Also, CA improved topsoil water stable macroaggregation (WSA = 415 mg g−1) when compared to CONV (251 mg g−1). Residue retention within conventional tillage (CONV + RES) led to small increases in topsoil aggregate stability (i.e. MWDds and WSA). Soil structural improvements were accompanied by a higher direct surface water infiltration. Micromorphological analysis of thin sections indicated a loose and highly biogenic soil microstructure in CA, whereas CONV was characterized by a physicogenic microstructure, despite similar soil bulk densities (SBD). SBD is thus a poor indicator of soil physical quality when comparing different tillage systems. Redundancy analysis illustrated that CA resulted in improvement in most parameters related to soil quality, especially at the soil surface, but significant yield increases were recorded only in 2004. CONV + RES lead to marginal improvements in soil quality with no yield increases.

This study compared the efficiency of geostatistical digital soil mapping (DSM) with conventional soil mapping (CSM) for updating soil class and property maps of a cultivated peatland in the Netherlands. For digital soil class mapping, the generalized linear geostatistical model was used. Digital mapping of the soil organic matter (SOM) content and peat thickness was done by universal kriging. The conventional soil class map was created by free survey, while the property maps were created with the representative profile description (RPD) and map unit means (MUM) methods. For each method, we computed the effort invested in the mapping in terms of the sampling and cost densities. The accuracies of the created soil maps were estimated from independent probability sample data. The results showed that for DSM, the cost density could be reduced by a factor of three compared with CSM without compromising accuracy. The map purity of both maps was around 55%. For conventional soil property mapping, the MUM maps were more accurate than the RPD maps. For SOM, CSM-MUM (RMSE 7.5%) performed better than DSM (RMSE 12.1%), although accuracy differences were not significant. For peat thickness, DSM (RMSE 23.3 cm) performed slightly better than CSM-MUM (RMSE 24.9 cm). Despite the differences in accuracy being small, the digital soil property maps were produced more efficiently. The cost density was a factor of 3.5 smaller. We conclude that for updating conventional soil maps in the Dutch peatlands, geostatistical DSM can be more efficient, although not necessarily more accurate, than CSM.

Continuing soil degradation remains a serious threat to future food security. Yet, global soil degradation assessments are based on qualitative expert judgments or remotely sensed quantitative proxy values that suffice to raise awareness but are too coarse to identify appropriate sustainable land management interventions. Studies in China and Sub Saharan Africa illustrate the considerable impact of degradation on crop production but also point to the need for solutions dependent on location specific agro-ecological conditions and farming systems.The development of a comprehensive approach should be feasible to better assess both extent and impact of soil degradation interlinking various scales, based on production ecological approaches and remote sensing to allow disentangling natural and human induced causes of degradation. A shared common knowledge base cataloguing hard-won location-specific interventions is needed for successfully preventing or mitigating degradation.

Soil classification systems are analysed to explore the potential of developing classification systems for catchments. Soil classifications are useful to create systematic order in the overwhelming quantity of different soils in the world and to extrapolate data available for a given soil type to soils elsewhere with identical classifications. This principle also applies to catchments. However, to be useful, soil classifications have to be based on permanent characteristics as formed by the soil forming factors over often very long periods of time. When defining permanent catchment characteristics, discharge data would therefore appear to be less suitable. But permanent soil characteristics do not necessarily match with characteristics and parameters needed for functional soil characterization focusing, for example, on catchment hydrology. Hydropedology has made contributions towards the required functional characterization of soils as is illustrated for three recent hydrological catchment studies. However, much still needs to be learned about the physical behaviour of anisotropic, heterogeneous soils with varying soil structures during the year and about spatial and temporal variability. The suggestion is made therefore to first focus on improving simulation of catchment hydrology, possibly incorporating hydropedological expertise, before embarking on a catchment classification effort which involves major input of time and involves the risk of distraction. In doing so, we suggest to also define other characteristics for catchment performance than the traditionally measured discharge rates. Such characteristics may well be derived from societal issues being studied, as is illustrated for the Green Water Credits program.

Land degradation is a global issue on par with climate change and loss of biodiversity, but its extent and severity are only roughly known and there is little detail on the immediate processes – let alone the drivers. Earth-observation methods enable monitoring of land degradation in a consistent, physical way and on a global scale by making use of vegetation productivity and/or loss as proxies. Most recent studies indicate a general greening trend, but improved data sets and analysis also show a combination of greening and browning trends. Statistically based linear trends average out these effects. Improved understanding may be expected from data-driven and process-modelling approaches: new models, model integration, enhanced statistical analysis and modern sensor imagery at medium spatial resolution should substantially improve the assessment of global land degradation.

The Carbon Benefits Project (CBP) is developing a standardized system for sustainable land management projects to measure, model and report changes in carbon stocks and greenhouse gas (GHG) emissions for use at varying scales. A global framework of soil organic carbon (SOC) stocks under native vegetation for application in data poor regions, using the simple assessment option of the CBP system, is presented. It considers default classes for climate and mineral soils as required for IPCC Tier 1 (empirical) level GHG inventories. Suitable soil profiles were extracted from an expanded version of the ISRIC-WISE database. Probable outliers within each climate–soil cluster were removed using a robust outlier-rejection procedure. Mean SOC stocks, to the IPCC reference depth of 30 cm (SOC30), vary greatly within each cluster. Overall, present estimates of SOC30 are lower than those listed in the 2006 IPCC Guidelines (though not necessarily in the statistical sense) that drew on a smaller selection of profiles from a more limited geographic area. They represent globally averaged values of SOC stocks under native vegetation that may differ from country/region specific values. Finer criteria for defining climate zones and soil classes, and replacement of default reference stocks and stock change factors with region-specific values, will be necessary to reduce uncertainty.

Soils knowledge dates to the earliest known practice of agriculture about 11,000 BP. Civilizations all around the world showed various levels of soil knowledge by the 4th century AD, including irrigation, the use of terraces to control erosion, various ways of improving soil fertility, and ways to create productive artificial soils. Early soils knowledge was largely based on observations of nature; experiments to test theories were not conducted. Many famous scientists, for example, Francis Bacon, Robert Boyle, Charles Darwin, and Leonardo da Vinci worked on soils issues. Soil science did not become a true science, however, until the 19th century with the development of genetic soil science, led by Vasilii V. Dokuchaev. In the 20th century, soil science moved beyond its agricultural roots and soil information is now used in residential development, the planning of highways, building foundations, septic systems, wildlife management, environmental management, and many other applications in addition to agriculture.

Globally applicable calibrations to predict standard soil properties based on infrared spectra may increase the use of this reliable technique. The objective of this study was to evaluate the ability of mid-infrared diffuse reflectance spectroscopy (4000-602 cm(-1)) to predict chemical and textural properties for a globally distributed soil spectral library. We scanned 971 soil samples selected from the International Soil Reference and Information Centre database. A high-throughput diffuse reflectance accessory was used with optics that exclude specular reflectance as a potential source of error. Archived data on soil chemical and physical properties were calibrated to first derivative spectra using partial least-squares regression. Good predictions for the spatially independent validation set were achieved for pH value, organic C content, and cation exchange capacity (CEC) (n = 291, r(2) of linear regression of predicted against measured values >= 0.75 and ratio of standard deviation of measured values to root mean square error of prediction (RPD) >= 2.0). The root mean square errors of prediction (RMSEP) were 0.75 pH units, 9.1 g organic C kg(-1) and 5.5 cmol(c) CEC kg(-1). Satisfactory predictions (r(2) = 0.65-0.75, RPD = 1.4-2.0) were obtained for exchangeable Mg concentration and clay content. The respective RMSEPs were 4.3 cmol(c) kg(-1) and 126 g kg(-1). Poorer predictions (r2 = 0.61 and 0.64) were achieved for sand and exchangeable Ca contents. Although RMSEP values are large relative to laboratory analytical errors, our results suggest a marked potential for the global spectral library as a tool for advice on land management, such as the classification of new samples into basic soil fertility classes based on organic C and clay contents, CEC, and pH. Further research is needed to test the stability of this global calibration on new data sets.

This paper discusses the study of taxonomic distance and pedodiversity by (1) deriving taxonomic distances for the World Reference Base for Soil Resources (WRB), (2) calculating pedodiversity indices at the global scale using the soil map of the world at a scale 1:25M, and (3) comparing traditional diversity measures which are based on abundance of soil individuals to measures that are based on taxonomic distance. Based on dominant identifiers in the WRB soil groups, taxonomic distances were derived between the soil groups and plotted in feature space. Using this information the soil's mean taxonomic distance for the world was calculated. The mean taxonomic distance combines the abundance and taxonomic relationship between soil groups and appears to be a useful index of pedodiversity. There is a good relation between mean taxonomic distance and climate or soil classes; areas with extreme temperatures and precipitation have the lowest pedodiversity. It was observed that areas with more detailed soil mapping units exhibit the largest pedodiversity and it was concluded that the measure of pedodiversity depends amongst others on the detail of the soil survey in an area.

HARTEMINK AE. 2010. The invasive shrub Piper aduneum in Papua New Guinea: a review. Piper aduncum is a shrub native to Central America. It is found in most Central and South American countries and also in the Caribbean and southern Florida (USA). In Asia and the Pacific, P aduncum occurs in Indonesia, Malaysia, Philippines, Papua New Guinea, Solomon Islands, Vanuatu, Fiji, Micronesia, American Samoa, Niue, the Marianas, Tonga, Samoa, the Cook Islands, Palatt and Hawaii (USA). Piper aduncum arrived in Papua New Guinea before the mid-1930s. From the 1970s, it started to dominate the secondary fallow vegetation in many parts of the humid lowlands. It invaded grassland areas and also appeared in the highlands up to 2100 in asl. The seeds are dispersed by birds, bats and wind, as well as by logging equipment and in some localities, by migrating people. The combination of its vigorous generative characteristics (small and abundant seeds), high growth rate and the accidental or intentional spreading has resulted ill its presence in most provinces of Papua New Guinea. In the 1990s, awareness of the spread of P aduncum grew and there was a corresponding increase in research interest. from a range of disciplines, e.g. pharmacology, agronomy, quarantine, forestry and taxonomy. The invasion of P aduncum has affected the farming system and livelihood of many rural people. Future research should focus on mapping its extent, and studying its agronomic, socio-economic and ecological effects, particularly its effect on biodiversity.

Water and fertilizer scarcity amid the increasing need of rice production challenges today’s agriculture. Integrated crop management (ICM) is a combination of water, crop, and nutrient management that optimizes the synergistic interaction of these components aiming at improving resource use efficiency, i.e. high productivity of water, land, and labor. The objectives of the study were to investigate the effects of crop establishment method, organic matter amendment, NPK management, and water management on yield of lowland rice. Five series of experiments were conducted at Sukamandi and Kuningan Experimental Stations, West Java. The first experiment was focused on crop establishment method, i.e. plant spacing and number of seedlings per hill. The second, third, and fourth experiments were directed to study the effect of NPK and organic matter applications on rice yield. The fifth experiments was designed to evaluate the effect of water management on rice yield. Results showed that 20 cm x 20 cm plant spacing resulted in the highest grain yield for the new plant type rice varieties. Organic matter and P fertilizer application did not significantly affect grain yield, but the yield response to P fertilization tended to be stronger with organic matter amendment. Split P application did not significantly increase grain yield. The use of a scale 4 leaf color chart reading resulted in a considerable N fertilizer saving without compromising rice yield. Intermittent irrigation technique saved water up to 55% without affecting yields, resulting in a 2-3 times higher water productivity.

This paper reviews current knowledge on changes in carbon stocks upon land use conversion in the Brazilian Cerrado. First, we briefly characterize the savanna ecosystem and summarize the main published data on C stocks under natural conditions. The effects of increased land use pressure in the Cerrado and current uncertainties of estimations of changes in land cover and land use are reviewed next. Thereafter, we focus on soil organic carbon (SOC) dynamics due to changes in land use, particularly conversion to pastures and soybean-based cropping systems, and effects of management practices such as soil fertilization, crop rotations and tillage practices. Most studies considered here suggest that more intensive agriculture, which include no-till practices and the implementation of best or recommended management practices (RMP), reduces SOC losses after land use conversion from conventional tillage-based, monocropping systems; however, these studies focussed on the first 0.3 m of soil, or less, and seldom considered full carbon accounting. To better estimate possible global warming mitigation with agriculture in the Cerrado more comprehensive studies are needed that analyse fluxes of the biogenic greenhouse gases (GHG; CO2, N2O and CH4) to determine the net global warming potential (GWP). Follow up studies should include the application of an integrated modelling system, comprised of a Geographic Information System (GIS) linked to dynamic modelling tools, to analyse SOC dynamics and make projections for possible changes in net C flows in the Cerrado region upon defined changes in soil use and management

In the 1990s and early 2000s, there was widespread pessimism on the status of soil science in most parts of the world. This was mainly due to dwindling research budgets, reduced number of students and the overall perception that soil science and pedology were dead and buried. Renewed interest in agriculture for food, feed and fuel has brought soils back onto the global research agenda. Soil erosion, nutrient depletion and pollution are key issues brought up in many recent reports by UN and other international organizations. The need for up-to-date and fine resolution soil information and the revival of soil research is highlighted and prioritized in several studies. There is increased interest in soils in the popular press and media, and soils have entered the policy arena. For the global soil science community, there are challenges ahead and there is a direct need to educate a new generation of soil scientists.

Cultivation of sugarcane for bioethanol is increasing and the area under sugarcane is expanding. Much of the sugar for bioethanol comes from large plantations where it is grown with relatively high inputs. Sugarcane puts a high demands on the soil because of the use of heavy machinery and because large amounts of nutrients are removed with the harvest; biocides and inorganic fertilizers introduce risks of groundwater contamination, eutrophication of surface waters, soil pollution, and acidification. This chapter reviews the effect of commercial sugarcane production on soil chemical, physical, and biological properties using data from the main producing areas. Although variation is considerable, soil organic C decreased in most soils under sugarcane and, also, soil acidification is common as a result of the use of N fertilizers. Increased bulk densities, lower water infiltration rates, and lower aggregate stability occur in mechanized systems. There is some evidence for high leaching losses of fertilizer nutrients as well as herbicides and pesticides; eutrophication of surface waters occurs in high-input systems. Soil erosion is a problem on newly planted land in many parts of the world. Trash or green harvesting overcomes many of the problems. It is concluded that sugarcane cultivation can substantially contribute to the supply of renewable energy, but that improved crop husbandry and precision farming principles are needed to sustain and improve the resource base on which production depends

An experiment including planted Tephrosia vogelii and Tithonia diversifolia fallow species and natural fallow was conducted at Maseno, Kenya, for assessing whether these fallows grown on a nutrient depleted land could produce sufficient green manure in six month period, whether their biomass retained on the same plots or transferred to continuously cropped plots with or without added P fertiliser could increase yield of consecutive maize crops and whether it is useful to regularly repeat these fallows on same plots. First fallow was established in randomized complete blocks with three replicates. At harvesting, biomass was recorded, then either incorporated in situ or transferred to continuous cropped plots split with and without added P fertiliser and monitored for the effect in improving consecutive maize crops. The second fallow was managed on this split plot design. The two-planted shrubs fallows produced more than 9 Mg total dry biomass and accumulated 154 to 234 kg N.ha-1, which were significantly higher compared to the production in the natural fallow. The shrubs were also superior to natural fallow for P accumulation (5-22 kg versus 2 kg.ha-1). The aboveground dry biomass harvested from planted T. vogelii and T. diversifolia and either incorporated in situ or transferred into continuously cropped plots increased maize yields by 2.5 folds compared to the unmanured crop, the control. Supplementing the organic materials with an additional 20 kg P inorganic fertilizer increased the 1st maize yield by about 40%. Productivity in the plots with T. vogelii or T. diversifolia aboveground biomass removal was low for the subsequent fallow and maize crops when compared to the performance in plots where biomass was incorporated. To achieve sustained yields of maize in depleted soils requires regular improved fallowing at least one season alternating with one season maize, and additional P inputs.

The renaissance was an intellectually-rich period following a period of stasis in the medieval period. Something analogous appears to be currently taking place in soil science where novel approaches to thought are combined with a revival of ideas from the past. Renewed interest in agriculture (food, feed, fuel) and numerous publications have brought soils back onto the global research agenda. The need for up-to-date and fine resolution soil information and the revival of soil research has been highlighted and prioritised in several recent studies by the UN and other international organizations. Soil erosion, nutrient depletion and pollution are key issues that have been brought up in many recent reports – in most cases in relation to environmental degradation, climate change and world-food production. There is also an increased interest in soils in the popular press and media, and soils have entered the policy arena in many countries and several continents. We guestimate that about €3.2 billion is annually spent on soil research in Europe, North America, and some of the main countries in Asia and Oceania. For the global soil science community, there are challenges ahead to address the questions raised in these reports. There is a whole set of new techniques and methodologies in the wings waiting to take centre stage. There is a direct need to educate a new generation of soil scientists and to increase the influx of soil science students in many universities. The soil science community should benefit from the current upsurge in soil science, but the community has to deliver the goods and information that is wanted and much needed.

National and sub-national scale estimates of soil organic carbon (SOC) stocks and changes can provide information land degradation risk, C sequestration possibilities and the potential sustainability of proposed land management plans. Under a GEF co-financed project, ‘The GEFSOC Modelling System’ was used to determine SOC stocks and projected stock change rates for four case study areas; The Brazilian Amazon, The Indo-Gangetic Plains of India, Kenya and Jordan. Each case study represented soil and vegetation types, climates and land management systems that are under represented globally, in terms of an understanding of land use and land management systems and the effects these systems have on SOC stocks. The stocks and stock change rates produced were based on detailed geo-referenced datasets of soils, climate, land use and management information. These datasets are unique as they bring together national and regional scale data on the main variables determining SOC, for four contrasting non-temperate eco-regions. They are also unique, as they include information on land management practices used in subsistence agriculture in tropical and arid areas. Implications of a greater understanding of SOC stocks and stock change rates in non-temperate areas are considered. Relevance to national land use plans are explored for each of the four case studies, in terms of sustainability, land degradation and greenhouse gas mitigation potential. Ways in which such information will aid the case study countries in fulfilling obligations under the United Nations Conventions on Climate Change, Biodiversity and Land Degradation are also considered. The need for more detailed land management data to improve SOC stock estimates in non-temperate areas is discussed.

The common GIS-based approach to regional analyses of soil organic carbon (SOC) stocks and changes is to define geographic layers for which unique sets of driving variables are derived, which include land use, climate, and soils. These GIS layers, with their associated attribute data, can then be fed into a range of empirical and dynamic models. Common methodologies for collating and formatting regional data sets on land use, climate, and soils were adopted for the project Assessment of Soil Organic Carbon Stocks and Changes at National Scale (GEFSOC). This permitted the development of a uniform protocol for handling the various input for the dynamic GEFSOC Modelling System. Consistent soil data sets for Amazon-Brazil, the Indo-Gangetic Plains (IGP) of India, Jordan and Kenya, the case study areas considered in the GEFSOC project, were prepared using methodologies developed for the World Soils and Terrain Database (SOTER). The approach involved three main stages: (1) compiling new soil geographic and attribute data in SOTER format; (2) using expert estimates and common sense to fill selected gaps in the measured or primary data; (3) using a scheme of taxonomy-based pedotransfer rules and expert-rules to derive soil parameter estimates for similar soil units with missing soil analytical data. The most appropriate approach varied from country to country, depending largely on the overall accessibility and quality of the primary soil data available in the case study areas. The secondary SOTER data sets discussed here are appropriate for a wide range of environmental applications at national scale. These include agro-ecological zoning, land evaluation, modelling of soil C stocks and changes, and studies of soil vulnerability to pollution. Estimates of national-scale stocks of SOC, calculated using SOTER methods, are presented as a first example of database application. Independent estimates of SOC stocks are needed to evaluate the outcome of the GEFSOC Modelling System for current conditions of land use and climate.

Rwanda is a poor country and land is scarce, with only 0.65 ha of suitable farmland per household. Literature search for identifying constraints and solutions to productive and sustainable agriculture and livestock production was carried out. The country is facing with increasing soil fertility depletion and erosion due to steep landscape, continuous cultivation and high but not well distributed rainfall. Crops adequately allocated to the 0.65 ha farmland may produce enough food for energy and protein, but not cooking oil; animal production for meeting fat requirements is already at the limit. Forest resources are insufficient to produce necessary poles, timber, fuel and other forest-related products; alternatives must be found. Strategies to raise agricultural production include soil and water conservation, fertility improvement, irrigation and drainage, high-yielding plant varieties, improved animal management, pest control and reduction of postharvest losses. Labour shortage at critical periods of agricultural operations can be reduced through appropriate mechanisation. Such improvements that are high demanding in investments may substantially raise crop and livestock production, allowing Rwanda to develop agro-industries and the commercial sector. Alternatively but carefully, preference may be given to investments in high-value exports that can pay for imports of food, fuel and other necessities.

The Global Environment Facility co-financed Soil Organic Carbon (GEFSOC) Project developed a comprehensive modelling system for predicting soil organic carbon (SOC) stocks and changes over time. This research is an effort to predict SOC stocks and changes for the Indian, Indo-Gangetic Plains (IGP), an area with a predominantly rice (Oryza sativa)–wheat (Triticum aestivum) cropping system, using the GEFSOC Modelling System and to compare output with stocks generated using mapping approaches based on soil survey data. The GEFSOC Modelling System predicts an estimated SOC stock for the IGP, India of 1.27, 1.32 and 1.27 Pg for 1990, 2000 and 2030, respectively, in the top 20 cm of soil. The SOC stock using a mapping approach based on soil survey data was 0.66 and 0.88 Pg for 1980 and 2000, respectively. The SOC stock estimated using the GEFSOC Modelling System is higher than the stock estimated using the mapping approach. This is due to the fact that while the GEFSOC System accounts for variation in crop input data (crop management), the soil mapping approach only considers regional variation in soil texture and wetness. The trend of overall change in the modelled SOC stock estimates shows that the IGP, India may have reached an equilibrium following 30–40 years of the Green Revolution. This can be seen in the SOC stock change rates. Various different estimation methods show SOC stocks of 0.57–1.44 Pg C for the study area. The trend of overall change in C stock assessed from the soil survey data indicates that the soils of the IGP, India may store a projected 1.1 Pg of C in 2030.

Airborne geophysics has been used at the catchment scale to map salt stores, conduits and soil variability, but few studies have evaluated its usefulness as a land management tool at the field scale. We respond to questions posed by land managers with: (1) comparison of airborne and ground-based electromagnetic surveys in the Lower Balonne catchment, Queensland, and (2) comparison with historical and anecdotal knowledge of landscape response in the country around Jamestown in mid-South Australia. In the Lower Balonne, direct comparison between ground electromagnetic survey (EM) and airborne electromagnetics (AEM) showed a strong relationship for both the absolute values and spatial patterns of conductivity. The penetration of AEM to greater than 100 m is valuable in defining hydrological barriers. In the Jamestown area, AEM conductivity corresponded well with specific outbreaks of salinity and observed variability in crop response; local inconsistencies at the ground surface could be resolved when sub-surface data were considered. AEM can provide valuable information at the field scale that is relevant to salinity management. Farmers can have confidence in any of these techniques (historical information, EM and AEM) and they may directly compare or integrate the results. (c) 2006 Elsevier B.V. All rights reserved.

Salinity and fresh water are two sides of the same coin, most conveniently measured by electrical conductivity; they can now be mapped rapidly in three dimensions using airborne electromagnetics (AEM). Recent developments in the calibration of airborne data against in-field measurements and additional information from radiometrics, magnetics and digital elevation models lend new insights into salinity, groundwater flow systems and water resources. Freshwater resources can be mapped, and salinity risk and the outcome of management interventions may be forecast, on the basis of the specific architecture of complete groundwater flow systems-enabling practical, cost-effective protection and development of water resources.

Arresting land degradation, not to mention remediation, requires long-term investment. Budgetary constraints mean that we have to prioritise, so decision makers need know exactly where and how severe is the degradation, and they need early warning to act in good time. The first global assessment using actual measurements was based on 23 years of Advanced Very High Resolution Radiometer (AVHRR) Normalised Difference Vegetation Index (NDVI) data at 8km resolution. Its aim was to identify black spots that should be investigated in the field – but hardly anybody did. The dataset now extends to 33 years, revealing both long-term trends and many reversals of trend. The areas hardest hit are sub-equatorial Africa, with outliers in the Ethiopian highlands and the Sahel; the Gran Chaco, Pampas and Patagonia; southeast Asia; the steppes from Moldova eastwards into Central Asia; the Russian far east and northeast China; and swaths of high-latitude forest. Since 2000, it has been possible to seamlessly scale up the coarse-resolution picture to 250m resolution using data from the Moderate- Resolution Imaging Spectroradiometer (MODIS) and to 30m resolution with Landsat. Now, thanks to commercial satellite data, we can zoom in, anywhere in the world, with 5m-resolution.

Soils are the largest terrestrial reservoir of organic carbon, yet great uncertainty remains in estimates of soil organic carbon (SOC) at global, continental, regional and local scales. Compared with biomass carbon, changes in SOC associated with changes in land use and management, or climate change, must be monitored over longer periods. The changes are small relative to the very large stocks present in the soil, as is their inherent variability. This requires sensitive measurement techniques and due consideration for the minimum detectable difference (MDD). Relationships between environmental and management factors and SOC dynamics can be established using experimental field trials, chronosequence studies and monitoring networks. Soil monitoring networks (SMNs), for example, can provide information on direct changes of SOC stocks through repeated measurements at a given site, as well as data to parameterize and test biophysical models at plot scale. Further, they can provide a set of point observations that represent the (mapped) variation in climate/soil/land use and management at national scale, allowing for upscaling. SMNs must be designed to detect changes in soil properties over relevant spatial and temporal scales, with adequate precision and statistical power. Most SMNs, however, are in the planning or early stages of implementation; few networks are located in developing countries, where most deforestation and land-use change is occurring. Within these monitoring networks, sites may be organized according to different sampling schemes, for example regular grid, stratified approach or randomized; different statistical methods should be associated with each of these sampling designs. Overall, there is a need for globally consistent protocols and tools to measure, monitor and model SOC and greenhouse gas emission changes to allow funding agencies and other organizations to assess uniformly the possible effects of the impacts of land-use interventions, and the associated uncertainties, across the range of world climate, soils and land uses.

80% of arable land in Africa has low soil fertility and suffers from physical soil problems. Additionally, significant amounts of nutrients are lost every year due to unsustainable soil management practices. This is partially the result of insufficient use of soil management knowledge. To help bridge the soil information gap in Africa, the Africa Soil Information Service (AfSIS) project was established in 2008. Over the period 2008-2014, the AfSIS project compiled two point data sets: the Africa Soil Profiles (legacy) database and the AfSIS Sentinel Site database. These data sets contain over 28 thousand sampling locations and represent the most comprehensive soil sample data sets of the African continent to date. Utilizing these point data sets in combination with a large number of covariates, we have generated a series of spatial predictions of soil properties relevant to the agricultural management--organic carbon, pH, sand, silt and clay fractions, bulk density, cation-exchange capacity, total nitrogen, exchangeable acidity, Al content and exchangeable bases (Ca, K, Mg, Na). We specifically investigate differences between two predictive approaches: random forests and linear regression. Results of 5-fold cross-validation demonstrate that the random forests algorithm consistently outperforms the linear regression algorithm, with average decreases of 15-75% in Root Mean Squared Error (RMSE) across soil properties and depths. Fitting and running random forests models takes an order of magnitude more time and the modelling success is sensitive to artifacts in the input data, but as long as quality-controlled point data are provided, an increase in soil mapping accuracy can be expected. Results also indicate that globally predicted soil classes (USDA Soil Taxonomy, especially Alfisols and Mollisols) help improve continental scale soil property mapping, and are among the most important predictors. This indicates a promising potential for transferring pedological knowledge from data rich countries to countries with limited soil data.

Information on the vegetation and landscape history of a region is often limited, and available data are hard to interprete. A concept is presented here on how a more comprehensive picture of the structure and development of landscapes and vegetations of the past can be gained by integrating the information of several disciplines. Archaeological field methods have been combined with methods used in landscape studies (geology, soil science, micromorphology) and vegetation studies (ecology, palynology and dendrochronology).This concept has been applied and tested during an integrated study of a buried woodland at Zwolle-Stadshagen (Province of Overijssel, the Netherlands). Many large wood remnants were found in a peat layer preserved below a thick clay deposit. The wood remnants were dated by using dendrochronology to the period between ca. 150 BC and AD 580 (ca. 2200 - 1400 cal. BP). Two phases could be distinguished in the development of the peat. The woodland consisted of a closed stand with ash, alder and oak as main species, in the first phase mostly resembling an alder carr, and in the second one the near-extinctFilipendulo-AlnetumPassage et Hofmann 1968. No evidence of exploitation of the woodland by man nor of animal foraging was found.The followed integrated procedure has led to a more substantiated reconstruction of the palaeo-environment with its wetland wood, but also of the influence of human activities on the palaeo-landscape and its woodlands, that could not have been obtained otherwise.

Soil fertility decline is perceived to be widespread in the upland soils of the tropics, particularly in sub-Saharan Africa. Most studies have used nutrient balances to assess the degree and extent of nutrient depletion; these have created awareness but suffer methodological problems as several of the nutrient flows and stocks are not measured. This chapter focuses on the assessment of soil fertility decline using soil chemical data (pH, organic C, total N, available P, cation exchange capacity (CEC), and exchangeable cations) that are routinely collected in soil surveys or for the assessment of fertilizer recommendations. Soil fertility decline can be assessed using a set of properties from different periods at the same site or from different land-use systems with the same soils. The former is easier to interpret; the latter can be rapidly collected but differences may be due to inherent differences and not have resulted from soil management. This study provides an analytical framework for the assessment of soil fertility decline and shows pitfalls and how they should be handled. Boundary conditions are presented that could be used in future studies on soil fertility management and crop productivity in the tropics.

A crop rotation system with various species was established on Alisols at Mata grassland site, oriental side of Zaire-Nile Watershed Divide (CZN), Rwanda. Inorganic and organic fertilizers were applied in various plots under randomized complete blocs with three replicates. Crop yield data for each season were recorded over a 9-year period. Results showed that there was very low or no harvest in plots without fertilizers. In plots with fertilizers, the yield generally increased but remained relatively low, few crops and varieties adapted to the Mata ecology, only potatoes [Solanum tuberosum] and finger millet [Eleusine coracana] responded well to fertilizers. Liming was absolutely necessary to get any acceptable crop yield improvement with NPK. High rate of rich farmyard manure was efficient and its effect was recorded up to 4 seasons after four regular seasonal applications. Mata compost (C:N >25, 0.3 g P kg-1) had little beneficial effect. One, four and half, and eight tonnes of lime per ha applied 3 times in 8 years increased soil pH (in water) but not up to 6.5. It is concluded that to improve food production at the CZN area, selection of crops and varieties to fit ecological conditions and amending soils to fit crops must be considered.

Information on the vegetation and landscape history of a region is often limited, and available data are hard to interprete. A concept is presented here on how a more comprehensive picture of the structure and development of landscapes and vegetations of the past can be gained by integrating the information of several disciplines. Archaeological field methods have been combined with methods used in landscape studies (geology, soil science, micromorphology) and vegetation studies (ecology, palynology and dendrochronology). This concept has been applied and tested during an integrated study of a buried woodland at Zwolle-Stadshagen (Province of Overijssel, the Netherlands). Many large wood remnants were found in a peat layer preserved below a thick clay deposit. The wood remnants were dated by using dendrochronology to the period between ca. 150 BC and AD 580 (ca. 2200 - 1400 cal. BP). Two phases could be distinguished in the development of the peat. The woodland consisted of a closed stand with ash, alder and oak as main species, in the first phase mostly resembling an alder carr, and in the second one the near-extinct Filipendulo-Alnetum Passage et Hofmann 1968. No evidence of exploitation of the woodland by man nor of animal foraging was found. The followed integrated procedure has led to a more substantiated reconstruction of the palaeo-environment with its wetland wood, but also of the influence of human activities on the palaeo-landscape and its woodlands, that could not have been obtained otherwise.

It is generally assumed that agricultural systems with perennial crops are more sustainable than systems with annual crops. Soil erosion is negligible and perennial crops have more closed nutrient cycling. Moreover, inorganic fertilizers are used more commonly in cash crops such as perennial crops so that soil fertility decline and nutrient mining are less likely to occur. In the past decades, considerable research has been devoted to the quantification of nutrient stocks and nutrient cycling in agro-ecosystems. This article reviews the main stocks and flows of nutrients in cocoa ecosystems for several cocoa-growing regions in the tropics. Most of the nitrogen is found in the topsoils, and less than 10% of the total N stock is in the cocoa and shade trees. Nitrogen in the annual litter fall is about 20 to 45% of the total N in the vegetation and 2 to 3% of the total N in the soil. The accumulation of potassium is low in cocoa ecosystems, and in most systems the total amount in the biomass is equivalent to the available P content in the topsoil. Phosphorus in the annual litter fall is about 10 to 30% of the total P in the vegetation and 10 to 40% of the available P in the soil. Potassium is a major nutrient in mature cocoa. Stocks of exchangeable K in the topsoil vary from 100 to 550 kg ha-1, and high K levels in the soil correspond to high K levels in the vegetation and litter. Partial nutrient balances were calculated that compares the losses, addition, and transfer of N, P, and K. The nutrient balance is negative in the absence of inorganic fertilizers, especially for K. Rainwash and litter fall are key components in the cycling of nutrients of cocoa ecosystems. The amount of nutrients transferred by rainwash is less than 8 kg ha-1 for N and P but varies from 38 to more than 100 kg ha-1 year-1 for K. Most soils under cocoa had a lower fertility when compared to primary forest, although soil chemical properties seem to settle at equilibrium levels. This review shows that large amounts of nutrients in cocoa ecosystems are transferred each year and that such nutrient cycling is essential for maintaining cocoa production

When the first official version of the WRB was released at the 17th World Congress of Soil Science at Montpellier in 1998, the fortunate decision was taken to freeze the system for at least eight years in order to allow thorough reflection and field data collection. Since then, the WRB has been tested worldwide and has proven to be very valuable. However, a lot of time was spent discussing the necessity either to add/delete qualifiers to Reference Soil Groups, their ranking, and the ultimate rationale behind the WRB system. This paper summarizes the discussions on the Reference Groups and the qualifiers and provides a rationale for their ranking. It appears that a unified system of ranking rigorously applied to all WRB Reference Groups makes little sense. Therefore, a logical ranking system is implemented that adjusts to the very character of the different Reference Groups while respecting, as much as possible, some general principles for overall ranking.

In order to understand nutrient dynamics in tropical farming systems with fallows, it is necessary to assess changes in nutrient stocks in plants, litter and soils. Nutrient stocks (soil, above ground biomass, litter) were assessed of one-year old fallows with Piper aduncum, Gliricidia sepium and Imperata cylindrica in the humid lowlands of Papua New Guinea. The experiment was conducted on a high base status soil (Typic Eutropepts), and in Papua New Guinea such soils are intensively used for agriculture. Soil samples were taken prior to fallow establisment and after one year when the fallows were slashed and above ground biomass and nutrients measured. The above ground and litter biomass of piper was 13.7 Mg dry matter ha-1, compared to 23.3 Mg ha-1 of gliricidia and 14.9 Mg ha-1 of imperata. Gliricidia produced almost 7 Mg ha-1 wood. Total above ground biomass returned to the soil when the fallows were slashed was the same for piper and gliricidia (8 Mg ha-1). Gliricidia accumulated the largest amounts of all major nutrients except for K, which was highest in the above ground piper biomass. Imperata biomass contained the lowest amount of nutrients. The largest stocks of C, N, Ca and Mg were found in the soil, whereas the majority of P was found in the above ground biomass and litter. Almost half of the total K stock of piper and gliricidia was in the biomass. During the fallow period, soil organic C significantly increased under gliricidia fallow whereas no net changes occurred in piper and imperata fallows. The study has shown large differences in biomass and nutrient stocks between the two woody fallows (piper, gliricidia) and between the woody fallows and the non-woody fallow (imperata). Short-term woody fallows are to be preferred above grass (imperata) fallows in the humid lowlands of Papua New Guinea because of higher nutrient stocks.

An airborne electromagnetic survey yields a three-dimensional map of ground electrical conductivity. The remotely sensed data are translated into salt load by field and laboratory calibration: drilling, measurement of borehole conductivity, electrical conductivity of 1 : 5 soil¿water extracts (EC1:5) and chemical analysis of pore fluids. Using these field measurements, the conductivity map is calibrated by constraining model parameters within limits defined by the measured values. Once the airborne data is calibrated, we can derive a regional constant (Ksalt) by comparing total ground conductivity with the mass of salt measured in bore samples. Pore fluid chemistry provides a definitive measure of salt, but EC1:5 values may be used, provided that the procedure ensures complete dispersal of clay aggregates to release all the salt. Maps of salt load can be generated from the conductance (total conductivity) maps using a geographical information system. Without calibration, airborne electromagnetic surveying is misleading. Properly calibrated, it provides a detailed, semi-quantitative, three-dimensional map of the distribution of salt in the landscape: a prerequisite for the effective management of salinity. Salt appearing at the surface and in streams is the result of processes operating throughout entire catenas and groundwater flow systems. Across the southeastern catchments of the Murray-Darling Basin, we found that salt is stored predominantly in thick clay horizons within the regolith (encompassing the soil cover, weathered parent material and unlithified sediments down to unweathered basement). Coarse materials, for example in prior stream channels, may serve as conduits for salt transport to rivers and the land surface

Shifting cultivation is common in the humid lowlands of Papua New Guinea but little is known about the effect of different fallows on sweet potato ( Ipomoea batatas ) yield and nutrient flows and pools in these systems. An experiment was conducted in which two woody fallow species ( Piper aduncum and Gliricidia sepium ) and a non-woody fallow species ( Imperata cylindrica ) were planted and slashed after one year. Sweet potato was grown for two consecutive seasons (1 year) after which the fallows and yields were compared with yields from continuously cropped plots. The experiment was conducted on a high base status soil (Typic Eutropepts). In the first season, marketable sweet potato yield after piper and imperata was about 11 t ha-1 but yields after gliricidia and under continuous cropping were significantly lower. Vine yield was similar for the continuously cropped plots and for the sweet potato after piper and gliricidia, but significantly lower than after imperata. The effects of the fallows on sweet potato yield lasted only one season. In the second season after the fallow, sweet potato yields were higher, which was contributed to lower rainfall. Nutrient budgets showed that the three fallow species (piper, gliricidia and imperata) added insufficient amounts of nitrogen, phosphorus and potassium for the removal of these nutrients by two consecutive seasons of sweet potato. From a yield point of view there seems no benefit in having a nitrogen-fixing fallow species like Gliricidia sepium in sweet potato based systems on high base status soils.

Shifting cultivation is common in the humid lowlands of Papua New Guinea but little is known about the effect of different fallows on sweet potato (Ipomoea batatas) yield and nutrient flows and pools in these systems. An experiment was conducted in which two woody fallow species (Piper aduncum and Gliricidia sepium) and a non-woody fallow species (Imperata cylindrica) were planted and slashed after one year. Sweet potato was grown for two consecutive seasons (1 year) after which the fallows and yields were compared with yields from continuously cropped plots. The experiment was conducted on a high base status soil (Typic Eutropepts). In the first season, marketable sweet potato yield after piper and imperata was about 11 t ha-1 but yields after gliricidia and under continuous cropping were significantly lower. Vine yield was similar for the continuously cropped plots and for the sweet potato after piper and gliricidia, but significantly lower than after imperata. The effects of the fallows on sweet potato yield lasted only one season. In the second season after the fallow, sweet potato yields were higher, which was contributed to lower rainfall. Nutrient budgets showed that the three fallow species (piper, gliricidia and imperata) added insufficient amounts of nitrogen, phosphorus and potassium for the removal of these nutrients by two consecutive seasons of sweet potato. From a yield point of view there seems no benefit in having a nitrogen-fixing fallow species like Gliricidia sepium in sweet potato based systems on high base status soils.

Land use alternatives are sought to boost agricultural income and productivity in Hainan Island, China. Regional differences exist in crop limitations, such as typhoon risk, low temperatures, poor soil fertility, and drought. In this study a crop zonation was made for a range of crops, among which is banana, as a way to: 1) establish areas for potential expansion for banana, and 2) identify limitations and options for crop and land management. A spatial soil and terrain database of Hainan Island (1:250000) was linked to the automated land evaluation system (ALES). The qualitative models were verified by comparing suitability maps with actual land use. The results may support policy formulation on issues such as alternatives to current land use, assessment of best management practices, and the need for fertilizer programmes.