Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    BENEFIT Partnership - 2019 annual report : Bilateral Ethiopian-Netherlands effort for food, income and trade partnership
    Alemu, Dawit ; Koomen, Irene ; Schaap, Mirjam ; Ayana, Amsalu ; Borman, Gareth ; Elias, Eyasu ; Smaling, Eric ; Getaw, Helen ; Becx, Gertjan ; Sopov, Monika ; Terefe, Geremew ; Schrader, Ted ; Tafere, Tewodros ; Vonk, Remko - \ 2020
    Wageningen : Wageningen Centre for Development Innovation (Report / Wageningen Centre for Development Innovation WCDI-20-094) - 211
    Going Bananas: A Food Systems Approach
    Brazao Vieira Alho, C.F. ; Hendriks, C.M.J. ; Stoorvogel, J.J. ; Vellema, S. ; Smaling, Eric - \ 2020
    - 33 p.
    The holistic concept of Food Systems (FS) has emerged as an attempt to tackle the multiple challenges regarding provision of sustainable and healthy diets for a growing population as described in e.g., the sustainable development goals. In this report, we focus on one commodity (bananas) in two contrasting cases: one focused on the banana export system in Costa Rica (CR) (including its exports to the Netherlands (NL)) and another on domestic supply and consumption in Uganda (UG). Here, we followed three conceptual frameworks of FS currently used in the literature. Furthermore, power relations between civil society, private sector and governmental agencies are also taken into consideration. We hypothesized that analysing the functioning of a particular commodity in a FS context adds value, compared to the more linear value chain approach, and will lead to better-informed policy, socio-economic and investment decisions. Our approach sheds light on some parts of the FS concepts that still need a more profound analysis. If we look at the differences in the presented FS frameworks, we think it is wise to look at building blocks as was done in this report, rather than trying to tackle the entire, complex system as a whole.
    BENEFIT Partnership – 2018 annual report : Bilateral Ethiopian-Netherlands Effort for Food, Income and Trade Partnership
    Alemu, Dawit ; Koomen, Irene ; Ayana, Amsalu ; Borman, Gareth ; Elias, Eyasu ; Smaling, Eric ; Getaw, Helen ; Becx, Gertjan ; Sopov, Monika ; Terefe, Geremew ; Schrader. Ted, ; Terefa, Tewodros ; Vonk, Remko - \ 2019
    Wageningen : Wageningen Centre for Development Innovation (Report / WDCI 19-053) - 199
    Explaining bread wheat (Triticum aestivum) yield differences by soil properties and fertilizer rates in the highlands of Ethiopia
    Elias, Eyasu ; Okoth, P.F. ; Smaling, E.M.A. - \ 2019
    Geoderma 339 (2019). - ISSN 0016-7061 - p. 126 - 133.
    Blend fertilizer - Bread wheat - Ethiopian highlands - Pedogenetic class

    Ethiopia faces major food security challenges. In spite of a modest level of fertilizer use, the percentage of wheat that is imported is substantial. The Ethiopian government has invested in the fertilizer sector, thereby also moving away from di-ammonium phosphate (DAP) to multi-nutrient blends (NPSZnB). Wheat fertilizer experiments were established in seven locations (three replications) in the highlands that represented the wide range of soils found in this area. The crop was exposed to DAP, NPS and to five levels of NPSZnB (50–300 kg/ha). All treatments included 100 kg/ha urea. The average wheat grain yield at the experimental sites, when all fertilizer treatments were averaged, ranged from <2 to >7 tons/ha. Soil sampling revealed that organic carbon (28%), total nitrogen and pH, and on the negative side, Fe and Mn concentrations, were significant drivers of yield differences. Fertilizers alone (when averaged for all experimental sites) could only explain 8% of yield differences, proving the ineffectiveness of blanket fertilizer recommendations. Blend fertilizers including micronutrients (NPSZnB) performed slightly but not significantly better than NPS alone or DAP alone. However, since the NP contents in the blend are slightly below those in NPS and DAP (particularly for P), a slight positive effect of Zn or B can be observed. On the other hand, Zn concentration in soils did not correlate significantly to wheat yields. Hence, determining the added effects of Zn and B remains subject for further research. Maximum yield gains to fertilizer application can only be achieved when fertilizers and soil property differences are analyzed jointly. In that case, 79% of yield differences were explained. Grouping soils into ‘recommendation windows’ then helps to come up with relevant and cost-effective fertilizer strategies. A simple calculation comparing the cost of wheat import with the cost of fertilizers needed to reach the current wheat consumption level in Ethiopia shows that the latter is by far the most cheaper option, but in need of smooth functioning of the entire value chain.

    'Dutch solutions for global challenges' in het agro-domein
    Smaling, Eric - \ 2018
    Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2874) - 37
    Rescue and renewal of legacy soil resource inventories: A case study of the Limpopo National Park, Mozambique.
    Cambule, A. ; Rossiter, D.G. ; Stoorvogel, J.J. ; Smaling, E.M.A. - \ 2015
    Catena 125 (2015). - ISSN 0341-8162 - p. 169 - 182.
    acid sulfate soils - carbon sequestration - resurrection - uncertainty - gambia - maps
    Many areas of developing countries are covered by legacy soil surveys, which, however are hardly used, as they are not available in digital form, used outdated standards, and have unknown quality. There have been very few attempts to rescue and renew these surveys, nor are there established criteria for the evaluation of their quality. We therefore decided to test the applicability of the Cornell Adequacy Criteria (CAC) to assess the quality of several renewed soil surveys in or near the Limpopo National Park, Mozambique (centroid: 23° 18' 55.57¿ S, 31° 55' 16.24¿ E), using the concepts of digital soilmapping. The qualitywas assessed formapping andmonitoring soil organic carbon (SOC), in terms of geodetic control, positional accuracy, map scale, and texture and adequacy of map legend. Metadata was attached to the renewed maps. SOC stocks were estimated qualitatively based on the description of themap units and quantitatively by themeasure-and-multiply approach fromlegacy laboratory measurements. The positional accuracy of georegistrationwas 13 to 45% of the square root of aMinimumLegible Area (MLA). Point and area-class layers could be created with high positional accuracy. However the index of maximumreductionwas high, indicating that the original publication scale could be reduced.Map unit definitions and overall information content of the surveyswere adequate. Integration of remotely sensed optical imagery and digital elevation models could be used to derive accurate contours, against which the positional accuracy of contour-basedmap borderswas assessed. Less than 30% of their lengths were within a distance equal to the square root of MLA. These sources could not be used to evaluate internal map borders, due to the subdued topography and major land-use changes since the original survey. Qualitative estimates of SOC are between lowand medium, consistent with other studies in this area. The CAC proved to be a useful framework for determining the fitness for use of legacy surveys.
    Adaptive livelihood strategies employed by farmers to close the food gap in semi-arid south eastern Zimbabwe
    Murungweni, C. ; Wijk, M.T. van; Giller, K.E. ; Andersson, J.A. ; Smaling, E.M.A. - \ 2014
    Food Security 6 (2014)3. - ISSN 1876-4517 - p. 313 - 326.
    climate-change - developing-countries - drought - adaptation - resilience - vulnerability - africa - management - responses - capacity
    Rural households in semi-arid areas of southern Africa are confronted with numerous hazards that threaten the household food base. The new wildlife policy of establishing transfrontier conservation areas aims to increase conservation of wildlife resources while improving local livelihoods. This policy can be better appreciated by local people if it embraces knowledge of the adaptive strategies they employ to close the food gap. We assessed how different households responded to the major hazard, drought, in order to gain insight into how these households addressed critical questions of food availability. Informal interviews, key informant interviews and focus group discussions were conducted to determine how households can be disaggregated according to their livelihood patterns and a questionnaire was applied to learn how each group responded to drought. Data were analysed within the three livelihood types that were identified and described at local level as cattle-based, crop-based and non-farm based. We found that factors that aggravated the effects of drought are specific to the different household types and their responses were also specific to that particular household type. Disaggregation of the livelihood types revealed within and between type relations and interactions that are important to people in order to cope. For example, even though cropping is an important activity across the three livelihood types, specifically in cattle and crop-based types, the non-farm type becomes important in restocking inputs after a serious drought through cross-border trading. Livestock and cross-border trading are important coping strategies for all three livelihood types, with the cattle-based trading cattle, the crop-based trading goats and poultry and the non-farm based linking with markets for trading livestock, drugs and restocked inputs for the cattle-based and crop-based groups. These linkages among livelihood types are important factors in reducing vulnerability to change that only become visible as a result of this disaggregation. We conclude that additional policies of enhancing the resilience of local food systems by stimulating across-border livestock trading and formal market set-up and enhancing systems of adaptation that are already in existence (e.g., crop production in the Banyeni) can add value to the success of transfrontier conservation areas in southern Africa.
    Soil organic carbon stocks in the Limpopo National Park, Mozambique: Amount, spatial distribution and uncertainty.
    Cambule, A. ; Rossiter, D.G. ; Stoorvogel, J.J. ; Smaling, E.M.A. - \ 2014
    Geoderma 213 (2014). - ISSN 0016-7061 - p. 46 - 56.
    residual maximum-likelihood - optimal sampling schemes - regionalized variables - land-use - terrain attributes - local estimation - data sets - sequestration - geostatistics - variability
    Many areas in sub-Saharan African are data-poor and poorly accessible. The estimation of soil organic carbon (SOC) stocks in these areas will have to rely on the limited available secondary data coupled with restricted field sampling. We assessed the total SOC stock, its spatial variation and the causes of this variation in Limpopo National Park (LNP), a data-poor and poorly accessible area in southwestern Mozambique. During a field survey, A-horizon thickness was measured and soil samples were taken for the determination of SOC concentrations. SOC concentrations were multiplied by soil bulk density and A-horizon thickness to estimate SOC stocks. Spatial distribution was assessed through: i) a measure-and-multiply approach to assess average SOC stocks by landscape unit, and ii) a soil-landscape model that used soil forming factors to interpolate SOC stocks from observations to a grid covering the area by ordinary (OK) and universal (UK) kriging. Predictions were validated by both independent and leave-one-out cross validations. The total SOC stock of the LNPwas obtained by i) calculating an area-weighted average from the means of the landscape units and by ii) summing the cells of the interpolated grid. Uncertainty was evaluated by the mean standard error for the measure-and-multiply approach and by the mean kriging prediction standard deviation for the soil-landscape model approach. The reliability of the estimates of total stockswas assessed by the uncertainty of the input data and its effect on estimates. The mean SOC stock from all sample points is 1.59 kg m-2; landscape unit averages are 1.13–2.46 kg m-2. Covariables explained 45% (soil) and 17% (coordinates) of SOC stock variation. Predictions from spatial models averaged 1.65 kg m-2 and are within the ranges reported for similar soils in southern Africa. The validation root mean square error of prediction (RMSEP) was about 30% of the mean predictions for both OK and UK. Uncertainty is high (coefficient of variation of about 40%) due to short-range spatial structure combined with sparse sampling. The range of total SOC stock of the 10,410 km-2 study area was estimated at 15,579–17,908 Gg. However, 90% confidence limits of the total stocks estimated are narrower (5–15%) for the measure-and-multiply model and wider (66–70%) for the soil-landscape model. The spatial distribution is rather homogenous, suggesting levels are mainly determined by regional climate.
    Building a near infrared spectral library for soil organic carbon estimation in the Limpopo National Park, Mozambique. August 2012
    Cambule, A. ; Rossiter, D.G. ; Stoorvogel, J.J. ; Smaling, E.M.A. - \ 2012
    Geoderma 183-184 (2012). - ISSN 0016-7061 - p. 41 - 48.
    diffuse-reflectance spectroscopy - quality indicators - quantitative-evaluation - spatial-distribution - nir spectroscopy - prediction - fertility - samples - model - mineralization
    Soil organic carbon (SOC) is a key soil property and particularly important for ecosystem functioning and the sustainable management of agricultural systems. Conventional laboratory analyses for the determination of SOC are expensive and slow. Laboratory spectroscopy in combination with chemometrics is claimed to be a rapid, cost-effective and non-destructive method for measuring SOC. The present study was carried out in Limpopo National Park (LNP) in Mozambique, a data- and access-limited area, with no previous soil spectral library. The question was whether a useful calibration model could be built with a limited number of samples. Across the major landscape units of the LNP, 129 composite topsoil samples were collected and analyzed for SOC, pH and particle sizes of the fine earth fraction. Samples were also scanned in a near-infrared (NIR) spectrometer. Partial least square regression (PLSR) was used on 1037 bands in the wavelength range 1.25–2.5 µm to relate the spectra and SOC concentration. Several models were built and compared by cross-validation. The best model was on a filtered first derivative of the multiplicative scatter corrected (MSC) spectra. It explained 83% of SOC variation and had a root mean square error of prediction (RMSEP) of 0.32% SOC, about 2.5 times the laboratory RMSE from duplicate samples (0.13% SOC). This uncertainty is a substantial proportion of the typical SOC concentrations in LNP landscapes (0.45–2.00%). The model was slightly improved (RMSEP 0.28% SOC) by adding clay percentage as a co-variable. All models had poorer performance at SOC concentrations above 2.0%, indicating a saturation effect. Despite the limitations of sample size and no pre-existing library, a locally-useful, although somewhat imprecise, calibration model could be built. This model is suitable for estimating SOC in further mapping exercises in the LNP
    Mapping the irrigated rice cropping patterns of the Mekong delta, Vietnam through hyper-temporal SPOT NDVI image analysis
    Nguyen, Thi Thu Ha ; Bie, C.A.J.M. de; Ali, A. ; Smaling, E.M.A. ; Hoanh, C.T. - \ 2012
    International Journal of Remote Sensing 33 (2012)2. - ISSN 0143-1161 - p. 415 - 434.
    multitemporal modis images - time-series - agriculture - areas - china - south - classification - expansion - systems - fields
    Successful identification and mapping of different cropping patterns under cloudy conditions of a specific crop through remote sensing provides important baseline information for planning and monitoring. In Vietnam, this information is either missing or unavailable; several ongoing projects studying options with radar to avoid earth observation problems caused by the prevailing cloudy conditions have to date produced only partial successes. In this research, optical hyper-temporal Satellite Pour l'Observation de la Terre (SPOT) VEGETATION (SPOT VGT) data (1998–2008) were used to describe and map variability in irrigated rice cropping patterns of the Mekong delta. Divergence statistics were used to evaluate signature separabilities of normalized difference vegetation index (NDVI) classes generated from the iterative self-organizing data analysis technique algorithm (ISODATA) classification of 10-day SPOT NDVI image series. Based on this evaluation, a map with 77 classes was selected. Out of these 77 mapped classes, 26 classes with prior knowledge that they represent rice were selected to design the sampling scheme for fieldwork and for crop calendar characterization. Using the collected information of 112 farmers’ fields belonging to the 26 selected classes, the map produced provides highly accurate information on rice cropping patterns (94% overall accuracy, 0.93 Kappa coefficient). We found that the spatial distributions of the triple and the double rice cropping systems are highly related to the flooding regime from the Hau and Tien rivers. Areas that are highly vulnerable to flooding in the upper part and those that are saline in the north-western part of the delta mostly have a double rice cropping system, whilst areas in the central and the south-eastern parts mostly have a triple rice cropping system. In turn, the duration of flooding is highly correlated with the decision by farmers to cultivate shorter or longer duration rice varieties. The overall spatial variability mostly coincides with administrative units, indicating that crop pattern choices and water control measures are locally synchronized. Water supply risks, soil acidity and salinity constraints and the anticipated highly fluctuating rice market prices all strongly influence specific farmers’ choices of rice varieties. These choices vary considerably annually, and therefore grown rice varieties are difficult to map. Our study demonstrates the high potential of optical hyper-temporal images, taken on a daily basis, to differentiate and map a high variety of irrigated rice cropping patterns and crop calendars at a high level of accuracy in spite of cloudy conditions
    Rice yields and yield gaps in Southeast Asia: Past trends and future outlook
    Laborte, A.G. ; Bie, C.A.J.M. de; Smaling, E.M.A. ; Moya, P.F. ; Boling, A.A. ; Ittersum, M.K. van - \ 2012
    European Journal of Agronomy 36 (2012)1. - ISSN 1161-0301 - p. 9 - 20.
    lowland rice - systems - locus - model
    Rice production must increase to meet future food requirements amid strong competition for limited resources. Yield gap analysis is a useful method to examine how large the ranges are between potential, desirable rice yields and those actually realized in farmers’ fields. We analyzed farmers’ yields in wet and dry seasons in four intensively cropped rice areas in Southeast Asia and explored opportunities for reducing the yield gap to meet future food requirements. We found yield gaps of 2.0–5.0 t ha-1 between average and climatic yield potential and 1.2–2.6 t ha-1 between average and best farmers’ yields. In relative terms, average yields varied between 43% and 75% of the climatic yield potential and 61% and 83% of the best farmers’ yields. Farmers with best yields were generally more educated, and used fertilizers and labor more efficiently than average farmers. The yield gaps between average and best farmers’ yields are higher in rice-importing countries (Indonesia and Philippines) compared with rice-exporting countries (Thailand and Vietnam). Assuming no change in diet, closing the existing yield gap between average and best-yielding farmers can sufficiently cover the yield increase needed for 2050 in the three countries, except for the Philippines, where yield increase must be even higher. Trend analysis of yield increases of a population of farmers in Central Luzon (Philippines), which included a learning curve analysis, well described the process of technology adoption from 1966 to 2008, leading to higher yields. Using this analysis, for the Philippines, we predicted yields to increase (from 2007/2008 to 2050) by only 18% with current cultivars, production technologies, and prevailing conditions. Therefore, structural changes are needed to boost farmers’ yields to close the yield gap faster. Investments in technology transfer and institutional arrangements are suggested
    Application of Fuzzy Cognitive Mapping in Livelihood Vulnerability Analysis
    Murungweni, C. ; Wijk, M.T. van; Andersson, J.A. ; Smaling, E.M.A. ; Giller, K.E. - \ 2011
    Ecology and Society 16 (2011)4. - ISSN 1708-3087 - p. 8 - 8.
    global environmental-change - bayesian belief networks - climate-change - food systems - models - resilience - maps - simulation - management - framework
    Feedback mechanisms are important in the analysis of vulnerability and resilience of social-ecological systems, as well as in the analysis of livelihoods, but how to evaluate systems with direct feedbacks has been a great challenge. We applied fuzzy cognitive mapping, a tool that allows analysis of both direct and indirect feedbacks and can be used to explore the vulnerabilities of livelihoods to identified hazards. We studied characteristics and drivers of rural livelihoods in the Great Limpopo Transfrontier Conservation Area in southern Africa to assess the vulnerability of inhabitants to the different hazards they face. The process involved four steps: (1) surveys and interviews to identify the major livelihood types; (2) description of specific livelihood types in a system format using fuzzy cognitive maps (FCMs), a semi-quantitative tool that models systems based on people’s knowledge; (3) linking variables and drivers in FCMs by attaching weights; and (4) defining and applying scenarios to visualize the effects of drought and changing park boundaries on cash and household food security. FCMs successfully gave information concerning the nature (increase or decrease) and magnitude by which a livelihood system changed under different scenarios. However, they did not explain the recovery path in relation to time and pattern (e.g., how long it takes for cattle to return to desired numbers after a drought). Using FCMs revealed that issues of policy, such as changing situations at borders, can strongly aggravate effects of climate change such as drought. FCMs revealed hidden knowledge and gave insights that improved the understanding of the complexity of livelihood systems in a way that is better appreciated by stakeholders.
    Where do we stand 20 years after the assessment of soil nutrient balances in sub-saharan Africa
    Smaling, E.M.A. ; Lesschen, J.P. ; Beek, C.L. ; Jager, A. de; Stoorvogel, J.J. ; Batjes, N.H. ; Fresco, L.O. - \ 2011
    In: World soil resources and food security / Lal, R, Stewart, B.A., Padstow, Great Britain : CRC Press (Advances in Soil Science ) - ISBN 9781439844502 - p. 499 - 537.
    Analysis of multi-temporal SPOT NDVI images for small-scale land-use mapping
    Bie, C.A.J.M. de; Khan, M.R. ; Smakhtin, V.U. ; Venus, V. ; Weir, M.J.C. ; Smaling, E.M.A. - \ 2011
    International Journal of Remote Sensing 32 (2011)21. - ISSN 0143-1161 - p. 6673 - 6693.
    cover change - vegetation cover - noaa-avhrr - drought - indexes - africa - plains - system - area
    Land-use information is required for a number of purposes such as to address food security issues, to ensure the sustainable use of natural resources and to support decisions regarding food trade and crop insurance. Suitable land-use maps often either do not exist or are not readily available. This article presents a novel method to compile spatial and temporal land-use data sets using multi-temporal remote sensing in combination with existing data sources. Satellite Pour l'Observation de la Terre (SPOT)-Vegetation 10-day composite normalized difference vegetation index (NDVI) images (1998–2002) at 1km2 resolution for a part of the Nizamabad district, Andhra Pradesh, India, were linked with available crop calendars and information about cropping patterns. The NDVI images were used to stratify the study area into map units represented by 11 distinct NDVI classes. These were then related to an existing land-cover map compiled from high resolution Indian Remote Sensing (IRS)-images (Liss-III on IRS-1C), reported crop areas by sub-district and practised crop calendar information. This resulted in an improved map containing baseline information on both land cover and land use. It is concluded that each defined NDVI class represents a varying but distinct mix of land-cover classes and that the existing land-cover map consists of too many detailed ‘year-specific’ features. Four groups of the NDVI classes present in agricultural areas match well with four categories of practised crop calendars. Differences within a group of NDVI classes reveal area specific variations in cropping intensities. The remaining groups of NDVI classes represent other land-cover complexes. The method illustrated in this article has the potential to be incorporated into remote sensing and Geographical Information System (GIS)-based drought monitoring systems
    Opportunities for enhancing crop yield in drought-prone south-east Zimbabwe
    Murungweni, C. ; Smaling, E.M.A. ; Wijk, M.T. van; Giller, K.E. - \ 2010
    In: Proceedings of the XIth ESA Congress Agro 2010, Montpellier, France, 29 August - 3 September 2010. - Montpellier, France : ESA - p. 985 - 986.
    Rice yields and yield gaps in Southeast Asia: Past trends and future outlook
    Laborte, A.G. ; Bie, C.A.J.M. de; Smaling, E.M.A. ; Moya, P.F. ; Ittersum, M.K. van - \ 2010
    In: Proceedings of Agro 2010 the XIth ESA Congress, Montpellier, France, September 29 to September 03, 2010. - Montpellier, France : ESA - ISBN 9782909613017 - p. 331 - 332.
    Integrated soil fertility management: Operational definition and consequences for implementation and dissemination
    Vanlauwe, B. ; Bationo, A. ; Chianu, J. ; Giller, K.E. ; Merckx, R. ; Mokwunye, U. ; Ohiokpehai, O. ; Pypers, P. ; Tabo, R. ; Shepherd, K.D. ; Smaling, E.M.A. ; Woomer, P.L. ; Sanginga, N. - \ 2010
    Outlook on Agriculture 39 (2010)1. - ISSN 0030-7270 - p. 17 - 24.
    smallholder farms - western kenya - exploring diversity - resource-allocation - nutrient flows - variability - tropics - maize
    Traditional farming systems in Sub-Saharan Africa depend primarily on mining soil nutrients. The African green revolution aims to intensify agriculture through the dissemination of integrated soil fertility management (ISFM). This paper develops a robust and operational definition of ISFM based on detailed knowledge of African farming systems and their inherent variability and of the optimal use of nutrients. The authors define ISFM as a set of soil fertility management practices that necessarily include the use of fertilizer, organic inputs and improved germplasm, combined with the knowledge on how to adapt these practices to local conditions, aimed at maximizing agronomic use efficiency of the applied nutrients and improving crop productivity. All inputs need to be managed in accordance with sound agronomic principles. The integration of ISFM practices into farming systems is illustrated with the dual-purpose grain legume-maize rotations in the savannas and fertilizer micro-dosing in the Sahel. Finally, the dissemination of ISFM practices is discussed
    Disaggregating and mapping crop statistics using hypertemporal remote sensing
    Khan, M.R. ; Bie, C.A.J.M. de; Keulen, H. van; Smaling, E.M.A. ; Real, R. - \ 2010
    International Journal of applied Earth Observation and Geoinformation 12 (2010)1. - ISSN 0303-2434 - p. 36 - 46.
    land-cover - time-series - modis data - ndvi data - vegetation - model - classification - climate - africa - europe
    Governments compile their agricultural statistics in tabular form by administrative area, which gives no clue to the exact locations where specific crops are actually grown. Such data are poorly suited for early warning and assessment of crop production. 10-Daily satellite image time series of Andalucia, Spain, acquired since 1998 by the SPOT Vegetation Instrument in combination with reported crop area statistics were used to produce the required crop maps. Firstly, the 10-daily (1998–2006) 1-km resolution SPOT-Vegetation NDVI-images were used to stratify the study area in 45 map units through an iterative unsupervised classification process. Each unit represents an NDVI-profile showing changes in vegetation greenness over time which is assumed to relate to the types of land cover and land use present. Secondly, the areas of NDVI-units and the reported cropped areas by municipality were used to disaggregate the crop statistics. Adjusted R-squares were 98.8% for rainfed wheat, 97.5% for rainfed sunflower, and 76.5% for barley. Relating statistical data on areas cropped by municipality with the NDVI-based unit map showed that the selected crops were significantly related to specific NDVI-based map units. Other NDVI-profiles did not relate to the studied crops and represented other types of land use or land cover. The results were validated by using primary field data. These data were collected by the Spanish government from 2001 to 2005 through grid sampling within agricultural areas; each grid (block) contains three 700 m × 700 m segments. The validation showed 68%, 31% and 23% variability explained (adjusted R-squares) between the three produced maps and the thousands of segment data. Mainly variability within the delineated NDVI-units caused relatively low values; the units are internally heterogeneous. Variability between units is properly captured. The maps must accordingly be considered “small scale maps”. These maps can be used to monitor crop performance of specific cropped areas because of using hypertemporal images. Early warning thus becomes more location and crop specific because of using hypertemporal remote sensing.
    Een beter milieu begint in Den Haag
    Kant, A. ; Jansen, P. ; Smaling, E.M.A. - \ 2009
    NRC-Handelsblad (2009). - ISSN 0002-5259 - 1 p.
    The fate of nitrogen in the Brazilian soybean chain
    Smaling, E.M.A. ; Roscoe, R. ; Lesschen, J.P. ; Bouwman, A.F. ; Comunello, E. - \ 2009
    In: Proceedings of the Conference on Integrated Assessment of Agriculture and Sustainable Development: Setting the Agenda for Science and Policy (AgSAP 2009), Egmond aan Zee, The Netherlands, 10-12 March 2009. - Wageningen University - p. 158 - 159.
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