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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    Kennisontwikkeling samen met stakeholders : ecosysteemdiensten in agrolandschappen
    Geertsema, W. ; Bianchi, F.J.J.A. ; Pulleman, M.M. ; Rijn, P.C.J. van; Rossing, W.A.H. ; Schaminee, J.H.J. ; Werf, W. van der - \ 2016
    Landschap : tijdschrift voor landschapsecologie en milieukunde 33 (2016)1. - ISSN 0169-6300 - p. 63 - 65.
    zuidhollandse eilanden - ecosystem services - fields - sustainable agriculture - landscape - farmers - public authorities - projects - workshops (programs) - zuidhollandse eilanden - ecosysteemdiensten - velden - duurzame landbouw - landschap - boeren - overheid - projecten - workshops (programma's)
    Ecosysteemdiensten spelen een belangrijke rol bij het verduurzamen van de landbouw. Maatregelen voor het versterken van ecosysteemdiensten kunnen genomen worden op verschillende ruimtelijke schaalniveaus, van perceel tot landschap. Voor maatregelen op landschapsschaal is samenwerking tussen boeren en andere belanghebbenden onmisbaar. Dit artikel beschrijft hoe onderzoekers via samenwerking met verschillende belanghebbenden kennis ontwikkelen voor versterking van ecosysteemdiensten voor een duurzamere landbouw.
    Vruchtbare gronden: Integrale bodemvisie & Bodembeoordeling en verbetering
    Haan, Janjo de - \ 2015
    arable farming - soil degradation - tillage - soil fertility - biodiversity - ecosystem management - soil-landscape relationships - soil water - fields - nematoda - soil surveys - rotations
    December 2015. Projectnummer 3750313900
    The emergence of institutional innovations in tourism: the evolution of the African Wildlife Foundation's tourism conservation enterprises
    Wijk, J.J. van; Duim, V.R. van der; Lamers, M.A.J. ; Sumba, D. - \ 2015
    Journal of Sustainable Tourism 23 (2015)1. - ISSN 0966-9582 - p. 104 - 125.
    entrepreneurship - creation - industry - fields - agency
    This paper examines the evolving and innovatory role of the African Wildlife Foundation (AWF), an NGO with charitable status, in dealing with the challenge of protecting wildlife outside state-protected areas. Drawing on the theoretical framework of institutional entrepreneurship, we historically trace AWF's engagement in conservation tourism, describing the complexities of how its actions evolved into the new organizational form of tourism conservation enterprises. We identify four key mechanisms – its “glocal” scope of action, awareness of policy and market voids, experimentation and hiring business professionals – that explain why AWF became aware, motivated and open to developing this organizational form. Lessons emerging from this process include that conservation NGOs should act as “opportunity seekers”, focus on incremental rather than radical innovations, note voids and ambiguities in governmental policies that provide opportunities for non-state actors to assume the role of institutional entrepreneur, and hire staff skilled in business, tourism and strategic management besides staff with the more conventional conservation skills in order to effectively engage in conservation tourism. Overall, the paper notes the importance of commercial conservation tourism approaches for the work of protected areas worldwide, and in using tourism as a poverty alleviation tool in less developed countries.
    Neerschalen van ruimtelijke informatie : Perceelsinformatie uit kaarten voor postcodegebieden
    Brus, D.J. ; Orton, T.G. ; Walvoort, D.J.J. ; Reijneveld, J.A. ; Oenema, O. ; Knotters, M. - \ 2014
    Landschap : tijdschrift voor landschapsecologie en milieukunde 31 (2014)3. - ISSN 0169-6300 - p. 165 - 168.
    bodemkwaliteit - organische stof - velden - landbouwgronden - kaarten - bepaling - kriging - statistische analyse - innovaties - soil quality - organic matter - fields - agricultural soils - maps - determination - kriging - statistical analysis - innovations
    Kaarten kunnen informatie geven over grotere eenheden, bijvoorbeeld postcodegebieden, of nog kleinere, zoals percelen. Met een variant op een interpolatietechniek is het mogelijk informatie te verkrijgen over een kleiner gebied. We illustreren dit aan de hand van organische stofgehalten in de bodem. De methodiek is breed toepasbaar op allerlei vormen van ruimtelijke informatie en maakt een betere benutting van data mogelijk.
    Quantification of viable eggs of the potato cyst nematodes (Globodera spp.) using either trehalose or RNA-specific Real-Time PCR
    Beniers, J.E. ; Been, T.H. ; Mendes, O. ; Gent-Pelzer, M.P.E. van; Lee, T.A.J. van der - \ 2014
    Nematology 16 (2014)10. - ISSN 1388-5545 - p. 1219 - 1232.
    infestation foci - rostochiensis - pallida - fields
    Two novel methods for the quantitative estimation of the number of viable eggs of the potato cyst nematodes (Globodera pallida and G. rostochiensis) were tested and compared with visual inspection. One is based on the loss of membrane integrity upon death and uses trehalose (a disaccharide) as a marker, the second test exploits the rapid degeneration of mRNA upon decease with a RNA-specific Real-Time Polymerase Chain Reaction (RT-PCR) assay. The viability of eggs in suspensions with different numbers of eggs was determined morphologically and was compared with both trehalose and elongation-factor-1-alpha (EF1a) mRNA measurements. The trehalose assay provided results that were close to those of the visual assessment using a microscope but only when samples contained low numbers of eggs. The lowest detectable value is 1.1 egg in the original sample and small differences in the number of viable eggs can be detected. Unfortunately, trehalose measurements reached a saturation limit at 1 cyst 10 µl-1; therefore, samples with nematode numbers above 262 eggs have to be diluted. The presence of dead cysts did not have a negative effect on the trehalose measurements. However, the use of egg suspensions instead of encysted eggs improved both the trehalose absorbance and the reliability of the measurements. When cysts were exposed to a treatment with allylisothiocyanate, the trehalose measurement detected the presence of more viable eggs than a hatching assay. The RT-PCR assay required a minimum of 30 eggs before detection occurred but can detect up to 8000 eggs in a 25 µl sample, which is an advantage when samples with high PCN infestations have to be processed. However, the confidence intervals (CI) of the RT-PCR assay are larger than those of the trehalose assay, which results in a high variation of single measurements. For example, at a density of 210 eggs in the original sample the 95% CI for the trehalose assay covers 191-228 eggs, and the 95% CI for the RT-PCR assay for G. pallida lies between 73 and 602 eggs and for G. rostochiensis between 59 and 745 eggs. Trials with field samples using both methods supported the laboratory tests. 95% of the field samples tested with the trehalose assay lie within the CI of the standard curve compared to 58% of the RT-PCR tested samples for G. pallida. The measurements of the field samples of G. pallida and G. rostochiensis populations using both methods resulted in larger numbers of viable eggs being detected compared to a hatching test. Neither of the investigated methods in their current state of development is optimal for use as a substitute for the visual inspection used in monitoring labs. The variance of the RT-PCR assay is too high if used for quantitative monitoring; the density range of eggs that can be detected using the trehalose assay is too small.
    Agricultural innovation platforms in West Africa: How does strategic institutional entrepreneurship unfold in different value chain contexts?
    Paassen, A. van; Klerkx, L.W.A. ; Adu-Acheampong, R. ; Adjei-Nsiah, S. ; Zannoue, E. - \ 2014
    Outlook on Agriculture 43 (2014)3. - ISSN 0030-7270 - p. 193 - 200.
    structural-change - fields - organizations - ghana
    Inspired by innovation system theory, donors promote innovation platforms (IPs) to enhance collaboration for development. However, IP practice and impact are diverse: hence the question arises of whether and how IP approaches are able to create institutional change for the benefit of smallholders. The authors present the experience of an action research programme in West Africa and analyse the cases from a dialectic perspective on institutional entrepreneurship. The results show that a researcher-initiated open IP approach with clear principles and in-depth analysis of the value chain context is able to create reasonably effective IP coalitions for smallholder development. In a mature value chain, it may be possible to mobilize high-level actors, but IPs often start at a lower level and apply a two-pronged approach. They focus primarily on research and communication to improve smallholder technical and entrepreneurial practices, while diligently mobilizing high-level actors to attain critical regulatory and/or market support. Mobilization success is limited in contentious environments.
    Institutional change and the quality of palm oil: an analysis of the artisanal processing sector in Ghana
    Osei-Amponsah, C. ; Stomph, T.J. ; Visser, L.E. ; Sakyi-Dawson, O. ; Adjei-Nsiah, S. ; Struik, P.C. - \ 2014
    International Journal of Agricultural Sustainability 12 (2014)3. - ISSN 1473-5903 - p. 233 - 247.
    In Ghana, most oil palm fruits are produced by smallholders and processed by female artisanal processors. However, the ensuing crude palm oil (CPO) is high in free fatty acids and therefore cannot be sold in remunerative local or export markets. An earlier diagnostic study indicated that two main factors cause the poor quality: the processing practice of leaving harvested fruits unprocessed for up to 21 days and the use of lorry tyres as fuel to cook the fruits. Furthermore, the tyre-burning practice affects the health of people working and living around the processing facilities. This study describes the effect of action research undertaken with processors and the creation of a stakeholder platform in which Chiefs, the District Assembly, and a Concertation and Innovation Group collaborated to address the issues. The emerging institutional changes are assessed against baseline information. Awareness was raised about the dangers of tyre-burning, and CPO quality was improved by establishing the optimal time to leave fruits before processing. However, the prevailing market circumstances led producers to opt to produce greater quantities of oil rather than better-quality oil.
    Toxic effects of hexaflumuron on the development of Cocccinella septempunctata
    Caihong, Yu ; Maoran, Fu ; Ronghua, Lin ; Yan, Zhang ; Liu, Yongquan ; Hui, Jiang ; Brock, T.C.M. - \ 2014
    Environmental Science and Pollution Research 21 (2014)2. - ISSN 0944-1344 - p. 1418 - 1424.
    insect growth-regulators - beneficial arthropods - pesticides - hymenoptera - fields - nontarget - impact - lethal - hym.
    Studying the toxic risk of pesticide exposure to ladybird beetles is important from an agronomical and ecological perspective since larval and adult ladybirds are dominant predators of herbivorous pest insects (e.g., aphids) in various crops in China. This article mainly deals with the long-term effects of a single application of the insect growth regulator hexaflumuron on Coccinella septempunctata. A 72- h and a 33-day toxicity test with hexaflumuron (single application) were performed, starting with the second instar larvae of C. septempunctata. Exposure doses in the long-term experiment were based on the estimated 72-h acute LR50 (application rate causing 50 % mortality) value of 304 g active ingredient (a.i.) ha-1 for second instar larvae of C. septempunctata. The long-term test used five hexaflumuron doses as treatment levels (1/50, 1/100, 1/200, 1/400, and 1/800 of the 72-h acute LR50), as well as a solvent control and blank control treatment. The measurement endpoints used to calculate no observed effect application rates (NOERs) included development time, hatching, pupation, adult emergence, survival, and number of eggs produced. Analyzing the experimental data with one-way analysis of variance showed that the single hexaflumuron application had significant effects on C. septempunctata endpoints in the 33-day test, including effects on development duration (NOER 1.52 g a.i. ha-1), hatching (NOER 3.04 g a.i. ha-1), pupation (NOER 3.04 g a.i. ha-1), and survival (NOER 1.52 g a.i. ha-1). These NOERs are lower than the reported maximum field application rate of hexaflumuron (135 g a.i. ha-1) in cotton cultivation, suggesting potential risks to beneficial arthropods.
    Change and diversity in smallholder rice-fish systems: Recent evidence and policy lessons from Bangladesh
    Dey, M.M. ; Spielman, D.J. ; Haque, A.B.M.M. ; Rahman, M.S. ; Valmonte-Santos, R. - \ 2013
    Food Policy 43 (2013). - ISSN 0306-9192 - p. 108 - 117.
    fresh-water prawn - floodplain aquaculture - southwest bangladesh - culture-systems - constraints - polyculture - fisheries - adoption - impacts - fields
    Efforts to unlock the genetic potential of both rice and fish, when combined with improvements in the management of rice-fish systems, can potentially increase agricultural productivity and food security in some of the poorest and most populous countries in Asia. In Bangladesh, estimates suggest that the country's potential rice-fish production system encompasses 2-3 million hectares of land. But despite three decades of research on biophysical and technical aspects of rice-fish systems, this potential has not been fully realized due to insufficient attention given to the social, economic, and policy dimensions of rice-fish system improvement. This paper provides a characterization of the diverse and changing nature of rice-fish systems in Bangladesh to shed new light on the economic viability of different rice-fish systems and recommend policy and investment options to accelerate the development of appropriate rice-fish technologies. Data are drawn from a novel subdistrict-level survey of fishery officers, a household/enterprise survey, focus group discussions, and a meta-review of the literature on aquaculture in the country, all of which were conducted in 2010-2011. Findings indicate that concurrent rice-fish systems, alternating rice-fish systems, and collectively managed systems offer considerable potential for increasing productivity and farm incomes in Bangladesh. Findings also suggest that while innovation in these rice-fish systems is being driven by households and communities, there is need for more supportive government policies and investments to enable further innovation. Policymakers need to develop effective regulations to promote feed and fish quality and quantity, for example. More rigorous analysis of the intended and unintended impacts of these policies and investments is also necessary. (C) 2013 Elsevier Ltd. All rights reserved.
    Co-evolution of landscape patterns and agricultural intensification:An example of dairy farming in a traditional Dutch landscape.
    Apeldoorn, D.F. van; Kempen, B. ; Sonneveld, M.P.W. ; Kok, K. - \ 2013
    Agriculture, Ecosystems and Environment 172 (2013). - ISSN 0167-8809 - p. 16 - 23.
    ecosystem services - grassland - resilience - flanders - quality - systems - fields
    The intensification of agricultural production strongly affects the characteristics of traditional rurallandscapes. Yet, the complexity of these landscapes also puts constraints on intensification. This inter-relationship leads to the hypothesis that the degree of intensification and locality are interdependent.Feedbacks between landscape and intensification often go unnoticed, while such a coupling would arguefor spatial explicit studies with a co-evolutionary perspective. In this study, we localized and quantifiedinteractions between landscape patterns and agricultural intensification for dairy farming systems in atraditional Dutch rural landscape. First, a conceptual diagram was made that maps causal interactionsbetween landscape patterns and production intensity. This conceptual diagram was converted to spatialexplicit descriptors of landscape patterns, such as hedge density, field size, clay content, ground waterhydrology and spatial explicit descriptors of management such as hedgerow change, field aggregation,field grazing days and fertilizer application. Next, these landscape patterns and management descrip-tors were linked to the current production intensity of farms such as total farm milk yield, milk yieldper cow and milk yield per hectare. These descriptors were tested for interrelations by applying two-sample Kolmogorov–Smirnov tests. We found that a higher milk production was significantly linked tolarger fields, fewer hedgerows, fewer grazing days, higher use of N-fertilizer and a decrease of nutrientcycling. Furthermore, production intensity was found to differ with the landscape pattern of clay con-tent and groundwater hydrology. On top of this landscape template, man-made patterns of field sizesand hedgerows from before 1930 are still visible in the current differences of milk production inten-sity. Current farm management was found to have relations with the hedgerows, field size, clay contentand groundwater hydrology. These relations hint at a co-evolution of landscape pattern and agriculturalintensification. Interestingly, the largest differences between descriptors of landscape pattern and inten-sity were found for similar values of clay content, groundwater hydrology and fertilizer use. We speculatethat these similar values indicate the existence of tipping points for diverging trajectories of intensifica-tion. Identification of such tipping points has implications for policies that deal with the future dynamicsof rural landscapes.
    Herstellen van akkers als onderdeel van een intact heidelandschap : de koppeling tussen arme heidegebieden en rijkere gronden
    Vogels, J. ; Jansman, H.A.H. ; Bobbink, R. ; Weijters, M. ; Verbaarschot, E. ; Den, P. ten; Versluijs, R. ; Waasdorp, S. - \ 2013
    Driebergen : Bosschap (Rapport OBN 179-DZ) - 179
    ecologisch herstel - heidegebieden - natuurgebieden - velden - bouwland - natuurwaarde - ecological restoration - heathlands - natural areas - fields - arable land - natural value
    De heidegebieden in Nederland herbergen een groot aantal habitattypen die in Europees opzicht erg waardevol zijn. Voorbeelden zijn droge en vochtige heide (H4030 en H4010), zandverstuivingen (H2330) en zwakgebufferde vennen (H3130). Deze heidegebieden liggen temidden van intensief gebruikt agrarisch gebied. Rechtstreeks gevolg hiervan lijkt dat karakteristieke faunasoorten van heidelandschappen nog steeds achteruit gaan in verspreiding. Een groeiend aantal beheerders experimenteert tegenwoordig met tijdelijke beakkering van kleine perceeltjes in of direct grenzend aan heideterreinen, met als doel de aan het heidelandschap verbonden diersoorten een grotere overlevingskans te geven. Daarnaast bestaan er bij beheerders vragen over het gewenste beheer van bestaande (extensieve) landbouwpercelen en wildakkers ten behoeve van de versterking van de natuurwaarden in nabij gelegen heidegebieden
    Weeds as important vegetables for farmers
    Cruz Garcia, G.S. ; Price, L.L. - \ 2012
    Acta Societatis Botanicorum Poloniae 81 (2012)4. - ISSN 0001-6977 - p. 397 - 403.
    edible wild plants - west-bengal - food plants - management - thailand - valley - mexico - fields - crops
    The objective of this study was to investigate the multiple uses and cognitive importance of edible weeds in Northeast Thailand. Research methods included focus group discussions and freelistings. A total of 43 weeds consumed as vegetable were reported, including economic, naturalized, agricultural and environmental weeds. The weedy vegetables varied considerably on edible parts, presenting both reproductive (flowers, fruits and seeds) and vegetative organs (shoots, leaves, flower stalks, stems or the whole aerial part). The results of this study show that weedy vegetables are an important resource for rice farmers in this region, not only as a food but also because of the multiple additional uses they have, especially as medicine. The fact that the highest Cognitive Salience Index (CSI) scores of all wild vegetables freelisted corresponded to weeds, reinforces the assertion that weeds are culturally cognitively important for local farmers as a vegetable source. This is a key finding, given that these species are targets of common pesticides used in this region.
    Workshop bodemkwaliteitsplan
    Molendijk, Leendert - \ 2012
    soil management - soil quality - soil suppressiveness - soil fertility - registration - fields - arable farming
    Body dynamics and hydrodynamics of swimming larvae: a computational study
    Li, G. ; Müller, U.K. ; Leeuwen, J.L. van; Liu, H. - \ 2012
    Journal of Experimental Biology 215 (2012). - ISSN 0022-0949 - p. 4015 - 4033.
    inertial flow regimes - escape response - kinematics - locomotion - wake - performance - waves - morphology - zebrafish - fields
    To understand the mechanics of fish swimming, we need to know the forces exerted by the fluid and how these forces affect the motion of the fish. To this end, we developed a 3-D computational approach that integrates hydrodynamics and body dynamics. This study quantifies the flow around a swimming zebrafish (Danio rerio) larva. We used morphological and kinematics data from actual fish larvae aged 3 and 5 days post fertilization as input for a computational model that predicted free-swimming dynamics from prescribed changes in body shape. We simulated cyclic swimming and a spontaneous C-start. A rigorous comparison with 2-D particle image velocimetry and kinematics data revealed that the computational model accurately predicted the motion of the fish's centre of mass as well as the spatial and temporal characteristics of the flow. The distribution of pressure and shear forces along the body showed that thrust is mainly produced in the posterior half of the body. We also explored the effect of the body wave amplitude on swimming performance by considering wave amplitudes that were up to 40% larger or smaller than the experimentally observed value. Increasing the body wave amplitude increased forward swimming speed from 7 to 21 body lengths per second, which is consistent with experimental observations. The model also predicted a non-linear increase in propulsive efficiency from 0.22 to 0.32 while the required mechanical power quadrupled. The efficiency increase was only minor for wave amplitudes above the experimental reference value, whereas the cost of transport rose significantly.
    Microwave links for rainfall estimation in urban environment: insights from an experimental setup in Luxembourg city
    Fenicia, F. ; Pfister, L. ; Kavetski, D. ; Matgen, P. ; Iffly, J.F. ; Hoffman, L. ; Uijlenhoet, R. - \ 2012
    Journal of Hydrology 464-465 (2012). - ISSN 0022-1694 - p. 69 - 78.
    path-averaged rainfall - dual-frequency - attenuation - resolution - fields - gauges - radar
    Although the theoretical aspects of rainfall monitoring through microwave links are quite well established, only few practical applications have evaluated this technique in an operational setting. Microwave links are of particular interest in urban areas, where high frequency measurements are needed due to the fast hydrological response of the system, and link networks are usually already in-place. This study presents the first results of an on-going experiment in Luxembourg-City, which includes two dual-frequency links and several rain gauges at intermediate locations along the links. The experimental set-up allows comparing rain rate estimates based on the individual frequencies as well as estimates based on the difference between the two frequencies. We compared several models for expressing the relationship between attenuation and rain rate, including different baseline estimation methods such as the traditional constant-baseline model and a one-parameter model based on a first order low-pass filter. The models were evaluated using a Bayesian approach and subjected to posterior scrutiny based on several diagnostics. In contrast to previous research, our results indicated that estimates based on the attenuation difference appeared poorer than the estimates based on individual frequencies. The one-parameter baseline estimation method provided consistently better results than the traditional constant-baseline method, which justifies the increased model complexity. Uncertainty of model predictions was relatively large for low intensity rainfall, which highlights one of the limitations of this technique. Models were validated in different periods and on different links, in some cases demonstrating large bias. Model parameters were generally well-identifiable, though uncertainty in the rainfall predictions appeared under-estimated in some cases.
    Modelling the role of algae in rice crop nutrition and soil organic carbon maintenance
    Gaydon, D.S. ; Probert, M.E. ; Buresh, R.J. ; Meinke, H.B. ; Timsina, J. - \ 2012
    European Journal of Agronomy 39 (2012). - ISSN 1161-0301 - p. 35 - 43.
    nitrogen-fixation - dynamics - fields
    Photosynthetic aquatic biomass (PAB – algae and other floodwater flora) is a significant source of organic carbon (C) in rice-based cropping systems. A portion of PAB is capable of fixing nitrogen (N), and is hence also a source of N for crop nutrition. To account for this phenomenon in long term simulation studies of rice-based cropping systems, the APSIM modelling framework was modified to include new descriptions of biological and chemical processes responsible for loss and gain of C and N in rice floodwater. We used well-tested algorithms from CERES-Rice, together with new conceptualizations for algal dynamics, in modelling the contribution of PAB to maintenance of soil organic C and soil N-supplying capacity in rice-based cropping systems. We demonstrate how our new conceptualization of PAB growth, turnover, and soil incorporation in flooded rice systems facilitates successful simulation of long-term soil fertility trials, such as the IRRI Long Term Continuous Cropping Experiment (35+ years), from the perspectives of both soil organic carbon levels and yield maintenance. Previous models have been unable to account for the observed maintenance of soil organic C in these systems, primarily due to ignoring inputs from PAB as a source of C. The performance of long-term rice cropping system simulations, with and without inclusion of these inputs, is shown to be radically different. Details of our modifications to APSIM are presented, together with evidence that the model is now a useful tool to investigate sustainability issues associated with management change in rice-based cropping systems.
    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
    Comparison of land nitrogen budgets for European agriculture by various modeling approaches
    Vries, W. de; Leip, A. ; Reinds, G.J. ; Lesschen, J.P. ; Bouwman, A.F. - \ 2011
    Environmental Pollution 159 (2011)11. - ISSN 0269-7491 - p. 3254 - 3268.
    no emissions - forest soils - n2o - inventory - ecosystems - balances - losses - fields - carbon - water
    A comparison of nitrogen (N) budgets for the year 2000 of agro-ecosystems is made for the EU 27 countries by four models with different complexity and data requirements, i.e. INTEGRATOR, IDEAg, MITERRA and IMAGE. The models estimate a comparable total N input in European agriculture, i.e. 23.3–25.7 Mton N yr-1, but N uptake varies more, i.e. from 11.3 to 15.4 Mton N yr-1 leading to total N surpluses varying from 10.4 to 13.2 Mton N yr-1. The estimated overall variation at EU 27 is small for the emissions of ammonia (2.8–3.1 Mton N yr-1) and nitrous oxide (0.33–0.43 Mton N yr-1), but large for the sum of N leaching and runoff (2.7–6.3 Mton N yr-1). Unlike the overall EU estimates, the difference in N output fluxes between models is large at regional scale. This is mainly determined by N inputs, differences being highest in areas with high livestock density.
    Weed seed predation in a phenologically late crop
    Westerman, P.R. ; Luijendijk, C.D. ; Wevers, J.D.A. ; Werf, W. van der - \ 2011
    Weed Research 51 (2011)2. - ISSN 0043-1737 - p. 157 - 164.
    setaria-faberi - abutilon-theophrasti - dynamics - fields - tillage - food
    Seed predation of weed seeds in crops depends on the seasonal overlap between seed availability and the activity period of the predators. Published data show that the activity period of seed predators is directly related to canopy cover. In phenologically early crops, such as cereals, maturation of leaves results in a decreasing cover prior to weed seed shed, resulting in lower seed losses than maximally possible. We hypothesised that there would be better temporal overlap in sugar beet, a phenologically late crop. The pattern of predation of Chenopodium album L. seeds was consistent over fields and years, low in July and August and gradually increasing until harvest in September/November. The patterns of seed production and shed, measured using seed traps, differed among weed species. The proportion of annual seed losses by predators calculated from these measurements ranged from 0.26 to 0.83, depending on the duration of seed exposure on the soil surface. As expected, sugar beet had better temporal overlap between predator activity and weed seed production, which may cause higher seed losses than previously reported for any other annual crop
    The benefits of using quantile regression for analysing the effect of weeds on organic winter wheat
    Casagrande, M. ; Makowski, D. ; Jeuffroy, M.H. ; Valantin-Morison, M. ; David, C. - \ 2010
    Weed Research 50 (2010)3. - ISSN 0043-1737 - p. 199 - 208.
    yield loss - management - crop - systems - competition - diversity - density - fields - maize - model
    P>In organic farming, weeds are one of the threats that limit crop yield. An early prediction of weed effect on yield loss and the size of late weed populations could help farmers and advisors to improve weed management. Numerous studies predicting the effect of weeds on yield have already been conducted, but the level of uncertainty about weed effect is expected to be very high in organic crops. It is thus more appropriate to provide farmers and advisors with distributions of possible production levels, rather than with point values. The purpose of this study was to estimate the effect of early weed density at the end of the tillering stage of organic winter wheat on subsequent yield and on late weed density at flowering, by using quantile regression. Results showed that this method can be applied to a hyperbolic model and to an allometric density-dependent model, to describe the distribution of yield values and of late weed density respectively, as functions of early weed density measurements. Mechanical weed control showed no significant effect on the relationship between early weed density and grain yield, but it decreased late weed density. Yield and late weed density distributions derived by quantile regression provided sound information on the possible effect of weeds on organic winter wheat production.
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