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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The power of statistical tests using field trial count data of non-target organisms in enviromental risk assessment of genetically modified plants
Voet, H. van der; Goedhart, P.W. - \ 2015
Agricultural and Forest Entomology 17 (2015). - ISSN 1461-9555 - p. 164 - 172.
herbicide-tolerant crops - farm-scale evaluations - varieties - design - maize - taxa - corn
Publications on power analyses for field trial count data comparing transgenic and conventional crops have reported widely varying requirements for the replication needed to obtain statistical tests with adequate power. These studies are critically reviewed and complemented with a new simulation study. The reasons for the different reports are elucidated and can be classified as additional (but hidden) replication, selection of favourable endpoints with low variation, and reporting at an unusual scale. A new simulation study was performed to investigate the relationship between statistical power and replication under a variety of data-generating and analysis methods. Approximately 60 replications should be sufficient to detect a 50% (two-fold) decrease in taxon numbers, provided that the coefficient of variation in the counts does not exceed 100%. Replication can be accomplished not only by using multiple blocks in a single trial, but also by repeating the experiment in multiple years and/or at different sites. With other (e.g. agronomic) treatment factors in the field trial, without interaction with variety, the effective replication can be increased by investigating the main variety effect summed over the other treatment factors. Repeated measures may also increase the power if the expected difference is equal over time and the time points are sufficiently spaced.
Strategic double cropping on Vertisols: A viable rainfed cropping option in the Indian SAT to increase productivity and reduce risk
Nageswara Rao, V. ; Meinke, H.B. ; Craufurd, P.Q. ; Parsons, D. ; Kropff, M.J. ; Anten, N.P.R. ; Wani, S.P. ; Rego, T.J. - \ 2015
European Journal of Agronomy 62 (2015). - ISSN 1161-0301 - p. 26 - 37.
nitrogen - field - soil - management - tillage - residue - maize - wheat - yield - corn
Our study suggests the possibility for transformational change in the productivity and risk profile of someof India’s rainfed cropping systems. In the semi-arid regions of Southern India, farmers traditionally cropsorghum or chickpea on Vertisols during the post-rainy season, keeping the fields fallow during the rainyseason. This practice avoids land management problems, but limits the potential for crop intensifica-tion to increase systems productivity. A long-term (15 year) experiment at ICRISAT demonstrated thatcropping during the rainy season is technically feasible, and that grain productivity of double croppedsorghum + chickpea (SCP–SCP) and mung bean + sorghum (MS–MS) sequential systems were higher thantheir conventional counterparts with rainy season fallow, i.e. fallow + post-rainy sorghum (FS–FS) and fal-low + post-rainy chickpea (FS–FCP). Without N application, mean grain yield of post-rainy sorghum in theMS–MS system was significantly greater (2520 kg ha-1per two-year rotation) than in the FS–FS system(1940 kg ha-1per two-year rotation), with the added benefit of the mung bean grain yield (1000 kg ha-1per two-year rotation) from the MS–MS system. In the SCP–SCP system the additional grain yield ofrainy sorghum (3400 kg ha-1per two-year rotation) ensured that the total productivity of this systemwas greater than all other systems. Double cropping MS–MS and SCP–SCP sequential systems had sig-nificantly higher crop N uptake compared to traditional fallow systems at all rates of applied nitrogen(N).The intensified MS–MS and SCP–SCP sequential systems without any N fertilizer applied recorded amuch higher median gross profit of Rs. 20,600 (US $ 375) and Rs. 15,930 (US $ 290) ha-1yr-1, respectively,compared to Rs. 1560 (US $ 28) ha-1yr-1) with the FS–FS system. Applying 120 kg of N ha-1considerablyincreased the profitability of all systems, lifting median gross profits of the sorghum + chickpea systemover Rs. 60,000 (US $ 1091) ha-1yr-1and the conventional system to Rs. 20,570 (US $ 374) ha-1yr-1. Thegross profit margin analysis showed that nitrogen is a key input for improving productivity, particularlyfor the double cropping systems. However, traditional systems are unviable and risky without N appli-cation in the variable climates of the semi-arid tropics. Together, our results show that on Vertisols insemi-arid India, double cropping systems increase systems’ productivity, and are financially more pro-fitability and less risky than traditional fallow post-rainy systems while further benefits can be achievedthrough fertilizer application.
Effect of temperature and duration of ensiling on in vitro degradation of maize silages in rumen fluid
Ali, M. ; Cone, J.W. ; Khan, N.A. ; Hendriks, W.H. ; Struik, P.C. - \ 2015
Journal of Animal Physiology and Animal Nutrition 99 (2015)2. - ISSN 0931-2439 - p. 251 - 257.
fermentation - kinetics - storage - forage - length - model - corn
The effects of ensiling temperature and duration of ensiling on the feeding quality of whole-crop maize (Zea mays L.) silages were investigated. Samples of one cultivar of maize plants were collected from two different fields, grown in different years on sandy soils. Samples were collected when the whole-plant dry matter content was approximately 330 g/kg. Maize plants were chopped and ensiled in mini silos at three different ambient temperatures (5, 12 and 18 °C). The ensiling temperature affected the ensiling fermentation processes, causing different rates of pH decline and different final pH values. Samples from the silos were taken after 0 (not ensiled, i.e. control), 4, 8 and 16 weeks of ensiling. The silage samples were not dried, but ground-frozen under liquid nitrogen to pass a 1-mm sieve. The gas production technique was used to evaluate the influence of the ensiling temperature and the duration of ensiling on the degradation of the silage samples in rumen fluid. The gas production was highest when the maize was ensiled at 12 °C (p <0.0001). An increase in ensiling duration caused a decrease in silage pH, accompanied by a decrease in gas production (p <0.0001). The decrease in gas production was linearly related to the decrease in pH at the three temperatures. The present study shows that both ensiling temperature and ensiling duration play a significant role in the rumen degradability of maize silage.
GIS-Based Multi-Criteria Analysis for Arabica Coffee Expansion in Rwanda
Nzeyimana, I. ; Hartemink, A.E. ; Geissen, V. - \ 2014
PLoS ONE 9 (2014)10. - ISSN 1932-6203
suitability evaluation - soil properties - land evaluation - prediction - framework - quality - yield - model - corn
The Government of Rwanda is implementing policies to increase the area of Arabica coffee production. Information on the suitable areas for sustainably growing Arabica coffee is still scarce. This study aimed to analyze suitable areas for Arabica coffee production. We analyzed the spatial distribution of actual and potential production zones for Arabica coffee, their productivity levels and predicted potential yields. We used a geographic information system (GIS) for a weighted overlay analysis to assess the major production zones of Arabica coffee and their qualitative productivity indices. Actual coffee yields were measured in the field and were used to assess potential productivity zones and yields using ordinary kriging with ArcGIS software. The production of coffee covers about 32 000 ha, or 2.3% of all cultivated land in the country. The major zones of production are the Kivu Lake Borders, Central Plateau, Eastern Plateau, and Mayaga agro-ecological zones, where coffee is mainly cultivated on moderate slopes. In the highlands, coffee is grown on steep slopes that can exceed 55%. About 21% percent of the country has a moderate yield potential, ranging between 1.0 and 1.6 t coffee ha(-1), and 70% has a low yield potential (<1.0 t coffee ha(-1)). Only 9% of the country has a high yield potential of 1.6-2.4 t coffee ha(-1). Those areas are found near Lake Kivu where the dominant soil Orders are Inceptisols and Ultisols. Moderate yield potential is found in the Birunga (volcano), Congo-Nile watershed Divide, Impala and Imbo zones. Low-yield regions (<1 t ha(-1)) occur in the eastern semi-dry lowlands, Central Plateau, Eastern Plateau, Buberuka Highlands, and Mayaga zones. The weighted overlay analysis and ordinary kriging indicated a large spatial variability of potential productivity indices. Increasing the area and productivity of coffee in Rwanda thus has considerable potential.
Measuring the impacts of production risk on technical efficiency: A state-contingent conditional order-m approach
Serra, T. ; Oude Lansink, A.G.J.M. - \ 2014
European Journal of Operational Research 239 (2014)1. - ISSN 0377-2217 - p. 237 - 242.
nonparametric frontier models - cheap talk - technologies - uncertainty - inference - corn
This article studies the influence of risk on farms' technical efficiency levels. The analysis extends the order-m efficiency scores approach proposed by Daraio and Simar (2005) to the state-contingent framework. The empirical application focuses on cross section data of Catalan specialized crop farms from the year 2011. Results suggest that accounting for production risks increases the technical performance. A 10% increase in output risk will result in a 2.5% increase in average firm technical performance. © 2014 Elsevier B.V. All rights reserved.
Protein source and dietary structure influence growth performance, gut morphology, and hindgut fermentation characteristics in broilers
Qaisrani, S.N. ; Moquet, P.C.A. ; Krimpen, M.M. van; Kwakkel, R.P. ; Verstegen, M.W.A. ; Hendriks, W.H. - \ 2014
Poultry Science 93 (2014)12. - ISSN 0032-5791 - p. 3053 - 3064.
feed particle-size - nutrient digestibility - amino-acids - canola-meal - parameters - chickens - wheat - corn - pigs - starters
An experiment with 210 male (Ross 308) 1-d-old broilers was conducted to test the hypothesis that a coarse diet improves performance of broilers fed a poorly digestible protein source. A highly digestible diet based on soybean meal was gradually replaced by a low digestible diet based on rapeseed meal (RSM) in 5 steps (RSM-0%, RSM-25%, RSM-50%, RSM-75%, and RSM-100%). Two diet structures (fine and coarse) were used as an additional factor. These 2 factors and their interactions were tested at different ages in a factorial arrangement with 10 dietary treatments. An increase in indigestible dietary protein negatively affected feed intake (P = 0.003), BW gain (P = 0.008), and feed conversion ratio (P = 0.034). This increase in dietary indigestible protein contents resulted in a decrease (P = 0.001) in total cecal volatile fatty acid concentration from 209.1 to 125.9 mmol/kg of DM digesta in broilers with increasing RSM in diets. Increase in the indigestible protein level, from RSM-0% to RSM-100%, resulted in a decrease (P = 0.042) in villus heights (1,782 vs. 1,574 µm), whereas crypt depths increased (P = 0.021; 237 vs. 274 µm). A coarse diet improved feed intake (P = 0.006), BW gain (P = 0.014), and feed conversion ratio (P = 0.009). Broilers fed coarse diets had approximately 11, 24, and 10% lower relative empty weights of the crop, proventriculus, and jejunum, respectively, whereas a 15% heavier gizzard was found compared with those fed the fine diets. Dietary coarseness resulted in approximately 16% lower gizzard pH, 21% greater villus heights, 27% lower crypt depths, 24% reduced branched-chain fatty acids, and 12% lower biogenic amines in the cecal digesta compared with broilers fed fine diets. In conclusion, feeding coarse particles improved broiler performance irrespective of digestibility of the diet. Hindgut protein fermentation can be reduced by coarse grinding of the diet.
Maize yield and quality in response to plant density and application of a novel plant growth regulator
Zhang, Q. ; Zhang, L. ; Evers, J.B. ; Werf, W. van der; Zhang, W. ; Duan, L. - \ 2014
Field Crops Research 164 (2014). - ISSN 0378-4290 - p. 82 - 89.
zea-mays l. - irrigated maize - spring wheat - grain-yield - corn - ethephon - height - climate - barley - ethyl
Farmers in China have gradually increased plant density in maize to achieve higher yields, but this has increased risk of lodging due to taller and weaker stems at higher plant densities. Plant growth regulators can be used to reduce lodging risk. In this study, for the first time, the performance of a mixture of the plant growth regulators ethephon and diethyl aminoethyl hexanoate (DA-6), called EDAH is tested at different plant densities and in different cultivars. Grain yield, yield components and grain quality as well as plant height and lodging percentage were determined in two years (2012 and 2013), using two maize hybrids, ZD 958 and Pioneer 335 at densities of 4.5, 6.0, 7.5 and 9.0 plants m-2 with and without foliar application of EDAH at 7 expanded leaves stage. EDAH significantly increased grain yield (by 7.8–8.0%), kernel number per ear (by 2.9–4.0%) and 1000-kernel weight (by 3.3–5.1%). Lodging percentage increased with plant density and was decreased by EDAH application in 2013. Optimal density was 7.5 plants m-2. The number of ears per unit ground area increased linearly with plant density, but number of kernels per ear and kernel weight showed an optimum. The two tested cultivars differed in yield and quality. No effects of EDAH on grain quality parameters (protein, oil and starch content) were found. We conclude that EDAH can improve lodging resistance and yield in maize, and that the yield effect of EDAH also occurs if lodging is not reduced.
Colour-encoded paramagnetic microbead-based direct inhibition triplex flow cytometric immunoassay for ochratoxin A, fumonisins and zearalenone in cereals and cereal-based feed
Peters, J. ; Thomas, D. ; Boers, E.A.M. ; Rijk, T.C. de; Berthiller, F. ; Haasnoot, W. ; Nielen, M.W.F. - \ 2013
Analytical and Bioanalytical Chemistry 405 (2013)24. - ISSN 1618-2642 - p. 7783 - 7794.
linked-immunosorbent-assay - surface-plasmon resonance - mycotoxin analysis - natural occurrence - food - b-1 - products - maize - corn - regulations
A combined (triplex) immunoassay for the simultaneous detection of three mycotoxins in grains was developed with superparamagnetic colour-encoded microbeads, in combination with two bead-dedicated flow cytometers. Monoclonal antibodies were coupled to the beads, and the amounts of bound mycotoxins were inversely related to the amounts of bound fluorescent labelled mycotoxins (inhibition immunoassay format). The selected monoclonal antibodies were tested for their target mycotoxins and for cross-reactivity with relevant metabolites and masked mycotoxins. In the triplex format, low levels of cross-interactions between the assays occurred at irrelevant high levels only. All three assays were influenced by the sample matrix of cereal extracts to some extent, and matrix-matched calibrations are recommended for quantitative screening purposes. In a preliminary in-house validation, the triplex assay was found to be reproducible, sensitive and sufficiently accurate for the quantitative screening at ML level. The triplex assay was critically compared to liquid chromatography–tandem mass spectrometry using reference materials and fortified blank material. Results for the quantification of ochratoxin A and zearalenone were in good agreement. However, the fumonisin assay was, due to overestimation, only suitable for qualitative judgements. Both flow cytometer platforms (Luminex 100 and FLEXMAP 3D) performed similar with respect to sensitivity with the advantages of a higher sample throughput and response range of the FLEXMAP 3D and lower cost of the Luminex 100.
The impact of climate and price risks on agricultural land use and crop management decisions
Lehmann, N. ; Finger, R. - \ 2013
Land Use Policy 35 (2013). - ISSN 0264-8377 - p. 119 - 130.
productivity - farmers - systems - policy - corn - profitability - uncertainty - algorithms - diversity - scenarios
This article aims to investigate the impacts of climate change and of lower and more volatile crop price levels as currently observed in the European Union (EU) on optimal management decisions, average income and income risks in crop production in Western Switzerland. To this end, a bioeconomic whole-farm model has been developed that non-parametrically combines the crop growth model CropSyst with an economic decision model using a genetic algorithm. The analysis focuses on the farm level, which enables us to integrate a wide set of potential adaptation responses, comprising changes in agricultural land use as well as crop-specific fertilization and irrigation strategies. Furthermore, the farmer's certainty equivalent is employed as objective function, which enables the consideration of not only impacts on average income but also impacts on income variability. The study shows that that the effects of EU crop prices on the optimal management decisions as well as on the farmer's certainty equivalent are much stronger than the effects of climate change. Furthermore, our results indicate that the impacts of income risks on the crop farm's optimal management schemes are of rather low importance. This is due to two major reasons: first, direct payments make up a large percentage of the agricultural income in Switzerland which makes Swiss farmers less vulnerable to market and climate volatility. Second, arable crop farms in Switzerland have by law to cultivate at least four different crops. Due to these diverse cropping systems and high government direct payments risk does neither under climate change, market liberalization nor combinations thereof, play a very decisive role in arable farming in Switzerland.
Processing Technologies and Cell Wall Degrading Enzymes To Improve Nutritional Value of Dried Distillers Grain with Solubles for Animal Feed: an in Vitro Digestion Study
Vries, S. de; Pustjens, A.M. ; Kabel, M.A. ; Salazar-Villanea, S. ; Hendriks, W.H. ; Gerrits, W.J.J. - \ 2013
Journal of Agricultural and Food Chemistry 61 (2013)37. - ISSN 0021-8561 - p. 8821 - 8828.
amino-acid - dietary fiber - growing pigs - nonstarch polysaccharides - corn - fermentation - gas - ingredients - ethanol - digestibility
Currently, the use of maize dried distillers grain with solubles (DDGS) as protein source in animal feed is limited by the inferior protein quality and high levels of non-starch polysaccharides (NSP). Processing technologies and enzymes that increase NSP degradability might improve digestive utilization of DDGS, enhancing its potential as a source of nutrients for animals. The effects of various combinations of processing technologies and commercial enzyme mixtures on in vitro digestion and subsequent fermentation of DDGS were tested. Wet-milling, extrusion, and mild hydrothermal acid treatment increased in vitro protein digestion but had no effect on NSP. Severe hydrothermal acid treatments, however, effectively solubilized NSP (48–78%). Addition of enzymes did not affect NSP solubilization in unprocessed or processed DDGS. Although the cell wall structure of DDGS seems to be resistant to most milder processing technologies, in vitro digestion of DDGS can be effectively increased by severe hydrothermal acid treatments.
Sustainability of European maize-based cropping systems: Economic, environmental and social assessment of current and proposed innovative IPM-based systems
Vasileiadisa, V.P. ; Moonen, A.C. ; Sattin, M. ; Otto, S. ; Pons, X. ; Kudsk, P.K. ; Veres, A. ; Dorner, Z. ; Weide, R.Y. van der; Marraccinib, E. ; Pelzerg, E. ; Angeving, F. ; Kiss, J. - \ 2013
European Journal of Agronomy 48 (2013). - ISSN 1161-0301 - p. 1 - 11.
conservation biological-control - ex ante assessment - agricultural sustainability - coniothyrium-minitans - model - future - crops - corn - performances - management
There is strong social and political pressure to reduce pesticide use in European agriculture. Evaluating the sustainability of cropping systems is a complex task due to the conflicting objectives underlying its economic, social and environmental dimensions. Multi-criteria assessment of different Integrated Pest Management (IPM) scenarios and evaluation of the most sustainable options at regional, national and European level is essential. Within the EU Network of Excellence ENDURE, two expert-based surveys were conducted (i.e. interviews), where experts from four European regions (northern region, Denmark and The Netherlands; central-eastern, Tolna and Békés counties in Hungary; south-western, Ebro Valley in Spain; southern, Po Valley in Italy) determined which are the main current maize-based cropping systems (MBCSs) in their region and proposed innovative IPM-based systems. The DEXiPM® (DEXi Pest Management) model for arable cropping systems was used to evaluate and compare the economic and environmental sustainability of these systems. The social sustainability was evaluated by adapting indicators of this model to the specificities of maize systems. The assessments showed that all innovative rotated MBCSs proposed in the four regions can have a higher environmental sustainability than and maintain the same economic sustainability as current rotated systems. These cropping systems are thus acceptable for testing under “real” field conditions. Only the innovative continuous maize system proposed in the central-eastern region was both economically and environmentally more sustainable than the current system. All innovative systems had a positive impact on work safety but according to local expert opinion producers and consumers are not ready to implement them or to accept their higher-priced products, with the exception of consumers in the northern region. These results suggest the need for European and regional policies to encourage the adoption of innovative rotated MBCSs that have positive agronomic and environmental impact through IPM implementation. The major constraints that inhibit this adoption were predominantly relating to (1) the lack of access that farmers have to the practical knowledge needed to effectively manage these systems and (2) the insufficient consumer awareness and acceptance of product improvements associated with IPM. To overcome these constraints supportive policy environments, well-functioning knowledge management systems (including good farmer support networks) and effective marketing is required
Seasonal nitrogen budgets of mature citrus trees on a sandy entisol
Morgan, K. ; Scholberg, J.M.S. ; Obreza, T. ; Wheaton, T. - \ 2012
Journal of Plant Nutrition 35 (2012)13. - ISSN 0190-4167 - p. 2009 - 2023.
uptake efficiency - leaching losses - soil - irrigation - mineralization - fertilization - management - sorghum - young - corn
Approximately 30% of Florida citrus is grown on well-drained Entisols with low nutrient-holding capacity, which are prone to high nitrogen (N) leaching losses. However, increasing application frequency of N-fertilizer via multiple fertigations does not increase crop yield, whereas in agronomic crops, such an approach typically enhances N uptake efficiency. We assessed seasonal tree N tissue concentration dynamics as affected by N rate for mature fourteen-year-old 'Hamlin' orange (Citrus sinensis L. Osbeck) trees on either Carrizo citrange (C. sinsensis L. Osbeck X Poncirus trifoliata L. Raf.) or Swingle citrumelo (C. paradisi Macf. X P. trifoliata L. Raf.) rootstocks. Nitrogen was applied as ammonium nitrate in six split fertigation applications with N target values of 179 and 269 kg ha(-1)yr(-1). Leaf, twig, and branch bark tissue N concentrations decreased through the spring to minima in May and June. This time period corresponds to a period of high N demand associated with both vegetative and reproductive growth. Tissue N concentrations increased from late spring minimums to fall and winter maximum concentrations. Reduction in branch bark and wood tissue N concentrations may have been due to a redistribution of N to leaf, twig, and fruit tissues in response to low N supply. The majority of the spring N should be supplied prior to May.
Application of an untargeted metabolomics approach for the identification of compounds that may be responsible for observed differential effects in chickens fed an organic and a conventional diet
Ruiz-Aracama, A. ; Lommen, A. ; Huber, M. ; Vijver, L. van de; Hoogenboom, L.A.P. - \ 2012
Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 29 (2012)3. - ISSN 1944-0049 - p. 323 - 332.
liquid-chromatography - phenolic-compounds - mass-spectrometry - farming system - food safety - antioxidant - health - corn - biosynthesis - metabolism
The aim of this study was to apply an untargeted NMR and LC-MS-based metabolomics approach to detect potential differences between an organically and a conventionally produced feed, which caused statistically significant differences in growth, in the response to an immunological challenge and in the gene expression profiles in the small intestine of laying hens. A fractionation procedure was set up to create multiple fractions of the feed, which were subsequently analysed by NMR and UPLC-TOF/MS operating in positive mode. Comparison of the profiles revealed that the most apparent differences came from the isoflavones in the soy as well as a compound with a molecular mass of 441.202 (M¿+¿1)+, which was identified as N,N'-diferuloylputrescine (DFP) and came from the corn. Whether the observed differences in effects are due to the higher levels of isoflavones and DFP is unclear, as is the fact whether the observed differences are typical for organic or conventional produced corn and soy. However, this study shows that this metabolomics approach is suitable for detecting potential differences between products, even in levels of compounds that would have been overlooked with a more targeted approach. As such, the method is suitable for a more systematic study on differences between conventionally and organically produced food. View full textDownload full text
Response to: Comments on the paper "A statistical assessment of differences and equivalences between genetically modified and reference plant varieties
Voet, H. van der; Perry, J.N. ; Amzal, B. ; Paoletti, C. - \ 2012
BMC Biotechnology 12 (2012). - ISSN 1472-6750
safety - grain - corn - l.
van der Voet et al. (2011) describe statistical methodology that the European Food Safety Authority expects an applicant to adopt when making a GM crop regulatory submission. Key to their proposed methodology is the inclusion of reference varieties in the
Modelling mycotoxin formation by Fusarium graminearum in maize in The Netherlands
Asselt, E.D. van; Booij, C.J.H. ; Fels-Klerx, H.J. van der - \ 2012
Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 29 (2012)10. - ISSN 1944-0049 - p. 1572 - 1580.
water activity - deoxynivalenol content - agricultural practices - zearalenone formation - fumonisin b-1 - zea-mays - ear rot - temperature - growth - corn
The predominant species in maize in temperate climates is Fusarium graminearum, which produces the mycotoxins deoxynivalenol and zearalenone. Projected climate change is expected to affect Fusarium incidence and thus the occurrence of these mycotoxins. Predictive models may be helpful in determining trends in the levels of these mycotoxins with expected changing climatic conditions. The aim of this study was to develop a model describing fungal infection and subsequent growth as well as the formation of deoxynivalenol and zearalenone in maize in The Netherlands. For this purpose, a published Italian model was used as a starting point. This model is a mixed empiric–mechanistic model that describes fungal infection during silking (based on wind speed and rainfall) and subsequent germination, growth and toxin formation (depending on temperature and water availability). Model input uses weather parameters and crop management factors, such as maize hybrid, sowing date, flowering period and harvest date. Model parameter values were obtained by fitting these parameters to deoxynivalenol and zearalenone measurements in Dutch maize, using national mycotoxin data from the years 2002–2007. The results showed that the adapted model is capable of describing the trend in average deoxynivalenol and zearalenone levels over these years. Validation with external data is needed to verify model outcomes. It is expected that the current model can be used to estimate the effect of projected climate change on trends in deoxynivalenol and zearalenone levels in the coming years.
Farmers' opinion on seed potato management attributes in Ethiopia: a conjoint analysis
Tufa, A.H. ; Meuwissen, M.P.M. ; Lans, I.A. van der; Lommen, W.J.M. ; Oude Lansink, A.G.J.M. ; Tsegaye, A. ; Struik, P.C. - \ 2012
Agronomy Journal 104 (2012)5. - ISSN 0002-1962 - p. 1413 - 1424.
nitrogen - design - corn
A low adoption of recommended seed potato (Solanum tuberosum L.) technologies in Ethiopia could be due to a lack of alternative seed potato production methods compatible with farmers’ economic and agro-ecological conditions. A conjoint analysis (a technique used to measure relative contribution of product attributes) was conducted to elicit farmers’ opinions on management attributes that they believed to affect yield and quality of potato. The study involved interviewing 324 farmers who grew seed potato in Jeldu and Welmera districts. The results showed that management attributes, such as storage method, hoeing combined with hill size, fertilizer rate (FR) and fungicide application (FA) frequency had larger effect on seed yield and quality than seed source, seed size, sprouting method, tillage frequency, and planting date. In both districts, using diffused light storage (DLS); hoeing twice, combined with big hills; and using recommended FR, combined with two FAs had significant positive effects on yield and quality of seed potato. In both districts, if all farmers switched to the best management attribute levels, potential increases in seed yield would be about two times the actual seed yield produced in 2010. The results suggest that it is possible to design better methods to produce seed potato compared with methods that farmers currently use. Extension personnel could use these results to recommend to farmers those management attributes that are the most important to improve yield and quality of seed potato in Ethiopia
Using hyperspectral remote sensing data for retrieving canopy chlorophyll and nitrogen content
Clevers, J.G.P.W. ; Kooistra, L. - \ 2012
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 5 (2012)2. - ISSN 1939-1404 - p. 574 - 583.
band vegetation indexes - higher-plant leaves - red-edge - spectral reflectance - leaf reflectance - narrow-band - model - meter - corn - management
Plant stress is often expressed as a reduction in amount of biomass or leaf area index (LAI). In addition, stress may affect the plant pigment system, influencing the photosynthetic capacity of plants. Chlorophyll content is the main driver for this primary production. The chlorophyll content is indirectly related to the nitrogen (N) content. In this paper emphasis is on estimation of canopy chlorophyll content and N content using remote sensing techniques. Hyperspectral reflectance data representing a range of canopies were simulated using the PROSAIL radiative transfer model at a 1 nm sampling interval. Various indices were tested for estimating canopy chlorophyll content. Subsequently, tests with field data were performed for sampling locations within an extensively grazed fen meadow using ASD FieldSpec measurements and within a potato field with a Cropscan radiometer for estimating canopy N content. PROSAIL simulations showed that the red-edge chlorophyll index (CIred edge) was linearly related to the canopy chlorophyll content over the full range of potential values (R-2 = 0.94). In contrast, highly non-linear relationships of chlorophyll content with most traditional red-edge indices were found. At the study sites the CIred edge was found to be a good and linear estimator of canopy N content (no chlorophyll was measured) for both the grassland site (R-2 = 0.77) and for the potato field (R-2 = 0.88). The latter number refers to plots showing no "luxury" N consumption. However, for the full potato data set, including highly fertilized plants, an exponential relationship yielded a better fit (R-2 = 0.85) as compared to a linear fit (R-2 = 0.65). Currently, this approach can, e. g., be applied with MERIS and Hyperion data and with the upcoming Sentinel-2 and -3 systems.
Using crop reflectance to determine sidedress N rate in potato saves N and maintains yield
Evert, F.K. van; Booij, R. ; Jukema, J.N. ; Berge, H.F.M. ten; Uenk, D. ; Meurs, E.J.J. ; Geel, W.C.A. van; Wijnholds, K.H. ; Slabbekoorn, J.J. - \ 2012
European Journal of Agronomy 43 (2012). - ISSN 1161-0301 - p. 58 - 67.
nitrogen status - fertilizer nitrogen - light reflectance - chlorophyll meter - vegetation index - management - soil - sensor - corn - recommendations
A low basal N application combined with in-season adjustment of the sidedressNrate has been proposed as a means to saveN in growing potato (Solanum tuberosum L.). We hypothesize that a measurement of canopy reflectance provides information which can be used to adjust sidedressNrate. The objective of our work was to develop and test a canopy reflectance-based Nsidedress system for potato in humid climates. In four years of experiments with ware potato on a sandy soil it was determined that the reflectance index WDVI correlates well with N uptake, that sidedressN should be applied at around the time of canopy closing, and that the sidedressNrate should be calculated as the difference between a (fixed) desired N uptake and a reflectance-based measurement of N uptake. The calculated N saving in these experiments was between 10 and 109 (average 56) kg N ha-1. The reflectance-based Nsidedress system was tested at an additional two locations, with ware potatoes on a loamy soil and with starch potatoes on a sandy soil, in two further years of experiments. N saving in these experiments was between 8 and 88 (average 44) kg N ha-1. In both sets of experiments, yields with the sidedress system were generally at the same level as yields obtained with recommended Nrates (basal N only). We conclude that the reflectance-based sidedressN system allows saving of N while maintaining yield
An innovation systems approach to institutional change: Smallholder development in West Africa
Hounkonnou, D. ; Kossou, D. ; Kuyper, T.W. ; Leeuwis, C. ; Nederlof, S. ; Roling, N. ; Sakyi-Dawson, O. ; Traoré, M. ; Huis, A. van - \ 2012
Agricultural Systems 108 (2012). - ISSN 0308-521X - p. 74 - 83.
agricultural-research - perspective - intensification - environment - management - prices - costs - corn
Sustainable intensification of smallholder farming is a serious option for satisfying 2050 global cereal requirements and alleviating persistent poverty. That option seems far off for Sub-Sahara Africa (SSA) where technology-driven productivity growth has largely failed. The article revisits this issue from a number of angles: current approaches to enlisting SSA smallholders in agricultural development; the history of the phenomenal productivity growth in the USA, The Netherlands and Green Revolution Asia; and the current framework conditions for SSA productivity growth. This analysis shows that (1) the development of an enabling institutional context was a necessary condition that preceded the phenomenal productivity growth in industrial and Green Revolution countries; and that (2) such a context is also present for successful SSA export crop production, but that (3) the context is pervasively biased against SSA’s smallholder food production. The article traces the origins of technology supply push (TSP) as a dominant paradigm that hinders recognition of the role of enabling institutions. The article then reviews the literature on institutional change and zooms in on Innovation Platforms (IPs) as a promising innovation system approach to such change. We describe the concrete experience with IP in the Sub-Sahara Challenge Program (SSA-CP) and in the Convergence of Sciences: Strengthening Innovation Systems (CoS-SIS) Program. The former has demonstrated proof of concept. The latter is designed to trace causal mechanisms. We describe its institutional experimentation and research methodology, including causal process tracing. --------------------------------------------------------------------------------
Fusarium spp. and levels of fumonisins in maize produced by subsistence farmers in South Africa
Ncube, E. ; Flett, B.C. ; Waalwijk, C. ; Viljoen, A. - \ 2011
South African Journal of Science 107 (2011)1-2. - ISSN 0038-2353 - p. 33 - 39.
quantitative detection - esophageal cancer - corn - moniliforme - mycotoxins - exposure - transkei
Fusarium spp. produce fumonisins - mycotoxins that are of importance to maize production in South Africa. Fumonisins have been associated with human oesophageal cancer and cause various diseases in animals that are of concern to the animal feed industry. Maize samples, collected from subsistence farm fields in the Eastern Cape, KwaZulu-Natal, Limpopo and Mpumalanga provinces of South Africa during the 2006 and 2007 growing seasons, were analysed for Fusarium spp. and contamination with fumonisins. Fusariumverticillioides was the most common Fusarium species in maize followed by F. subglutinans and F. proliferatum. Levels of contamination with fumonisins ranged from 0 µg/g to 21.8 µg/g, depending on the region where samples were collected. Levels of fumonisins were highest in northern KwaZulu-Natal (Zululand) where 52% and 17% of samples collected in 2006 and 2007, respectively, exceeded 2 µg/g. Regression analyses showed a positive correlation between fumonisin-producing Fusarium spp. determined by real-time polymerase chain reaction and concentration of fumonisins (r = 0.93). Many samples from Zululand, and some from Mokopane (Limpopo) and Lusikisiki (Eastern Cape), contained fumonisins at levels well above the maximum levels of 2 µg/g set by the Food and Drug Administration (USA) and therefore also the limit of 1 µg/g set by the European Union for food intended for direct human consumption. Regulations governing contamination of grain with fumonisins are not yet implemented in South Africa. The high incidence of fumonisins in subsistence farming systems indicates the need for awareness programmes and further research
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