Saskia L. G. E. Burgers (original) (raw)

Papers by Saskia L. G. E. Burgers

Research paper thumbnail of Pragmatische gevoeligheids- en onzekerheidsanalyse in het regionale waterbeheer

De komende jaren voert Waterschap Veluwe maatregelen uit ter voorkoming van wateroverlast. Om de ... more De komende jaren voert Waterschap Veluwe maatregelen uit ter voorkoming van wateroverlast. Om de eff ecten hiervan in het oppervlaktewatersysteem te bepalen, gebruikt het waterschap detailmodellen van haar watersysteem. Vanwege het ontbreken van meetgegevens is kalibratie beperkt mogelijk. Om die reden heeft de stochastische gevoeligheids-en onzekerheidsanalyse die het waterschap voor één stroomgebied uitvoerde, extra waarde. Met Monte Carlo-simulaties is op een pragmatische wijze inzichtelijk gemaakt welke parameters de grootste onzekerheid genereren in de maximale waterstand en het maximale debiet.

Research paper thumbnail of Sturen op nitraat: nitraatconcentraties in het grondwater en mogelijke indicatoren

Research paper thumbnail of Sturen op nitraat: waar zitten de knoppen?

Bemesting, beweiding en scheuren van grasland hebben een groot effect op de nitraatconcentratie i... more Bemesting, beweiding en scheuren van grasland hebben een groot effect op de nitraatconcentratie in het grondwater. Op maïsland heeft het achterwege laten van kunstmest, maar ook het achterwege laten van de bemesting van het vanggewas, behoorlijk effect. Dit blijkt uit een analyse van melkveebedrijven op zandgronden in het project Koeien & Kansen. De analyse omvat de effecten van bedrijfsvoering en van bodem, waterhuishouding en weer op de nitraatconcentratie

Research paper thumbnail of Deskstudie naar de mogelijkheden voor het aanwijzen van fosfaatarme gronden op basis van P-PAE

Het Bedrijfslaboratorium voor Grond- en Gewasonderzoek hanteert sinds twee jaar het onderzoekspak... more Het Bedrijfslaboratorium voor Grond- en Gewasonderzoek hanteert sinds twee jaar het onderzoekspakket Plant Available Elements (PAE). In dit pakket is fosfaat opgenomen (P-PAE). P-PAE is niet opgenomen in het protocol voor het aanwijzen van landbouwpercelen die in aanmerking komen voor een verhoogde fosfaatgebruiksnorm. Een deskstudie naar het opnemen van P-PAE als derde methode voor het aanwijzen van fosfaatarme gronden is uitgevoerd.

Research paper thumbnail of Predictive modeling of deoxynivalenol in winter wheat in The Netherlands

Research paper thumbnail of De betekenis van grondonderzoek met 0,01 M calciumchloride als basis voor het kaliumbemestingsadvies van bouwland

Research paper thumbnail of Grondonderzoek met 0.01 M CaCl2 als basis voor het kaliumbemestingsadvies van akkerbouwland. Herijking van de kaliumbemestingsadviezen

Research paper thumbnail of Nitrogen rate, surplus or residue? Performance of selected indicators for nitrate leaching

Research paper thumbnail of 1.3. 2 Gebruik van kwantitatieve TaqMan PCR in epidemiologisch onderzoek naar het optreden van aarfusarium in tarwe

Research paper thumbnail of Population dynamics in the belowground food webs in two different agricultural systems

Agriculture, Ecosystems & Environment, 1994

The biomass of 17 different groups of organisms was established every 6 weeks during 1 year in tw... more The biomass of 17 different groups of organisms was established every 6 weeks during 1 year in two arable fields cropped to winter wheat; one field was under conventional management (CONV) and the other under integrated management (INT). Bacteria showed the highest average biomass, followed by earthworms (INT only) and amoebae. Most of the groups of organisms had higher biomasses in INT than in CONV. The difference was statistically significant for protozoans, bacterivorous, fungivorous, and phytophagous nematodes and earthworms. Predatory Collembola, cryptostigmatic and bacterivorous mites, and enchytraeids showed a smaller biomass in INT than in CONV. The annual biomass production for each group was estimated using simulation model calculations. Bacteria showed the highest production followed by amoebae and earthworms (INT only). Most of the groups showed a higher biomass production in INT than in CONV. Exceptions were predatory and nematophagous mites, predatory and omnivorous Collembola, and enchytraeids. The total annual production was approximately 32 kg C ha-~ cm-~ depth in CONV and approximately 57 kg C in INT. The population dynamics were analysed by hierarchical cluster analysis. Four different clusters were found in CONV and INT. Bacteria, fungi, protozoans, bacterivorous nematodes and predatory mites showed the same trend in population dynamics in CONV and INT. All other groups showed different population dynamics in CONV and INT. This observation and the composition of these clusters suggested different conditions in CONV and INT.

Research paper thumbnail of Dynamics of microorganisms, microbivores and nitrogen mineralisation in winter wheat fields under conventional and integrated management

Agriculture, Ecosystems & Environment, 1994

To reduce environmental problems, integrated farming has been proposed, which may involve a consi... more To reduce environmental problems, integrated farming has been proposed, which may involve a considerable reduction of fertiliser-N input. A reduced fertiliser-N input must be compensated for by a higher N mineralisation from organic matter. To reduce losses and to facilitate optimal use of the N mineralised for crop growth, knowledge of the effects of management on soil organisms and on their role in N cycling is needed. Therefore, biomass and activity of bacteria, biomasses of fungi, bacterivorous amoebae, flagellates and nematodes, and in situ N mineralisation were monitored during a full year in a winter wheat field under conventional management (CONV) and integrated management (INT). Fungal biomass was about 100-fold lower than bacterial biomass. The average bacterial biomass was not significantly higher in INT than in CONV, whereas amoebae and nematodes were 64% and 22% higher, respectively. Average N mineralisation was 30% higher in INT. The differences are attributed to the approximately 30% higher organic matter content of INT. Bacterial biomass and frequency of dividing-divided cells (FDDC) were relatively low in December and January, probably owing to temperatures just above 0°C. At about 5°C in February and March, relatively high FDDC values and a doubling of bacteria occurred. During summer, FDDC values were relatively low and bacterial numbers were stable, probably owing to nutrient limitation. After harvest and skim ploughing, rapid increases in FDDC and bacteria were found. In the non-fumigated INT field, protozoan peaks coincided with the bacterial peak, whereas in CONV bacterivorous fauna were drastically reduced by soil fumigation. Nevertheless, the bacterial peaks were similar in CONV and INT, indicating that bacteria were not controlled by bacterivores. Nitrogen mineralisation was relatively low in winter. The increased bacterial growth in February and March, and in September appeared to enhance immobilisation rather than mineralisation of N. During the growing season from April to the end of August, bacterial growth was relatively low and N mineralisation was relatively high. This probably resulted from bacterivore feeding and from substrate-or nutrient-limited bacteria with a low growth

Research paper thumbnail of Mushroom Worker??s Lung

Journal of Occupational and Environmental Medicine, 1992

Indoor cultivation of the edible mushroom Shii-take (Lentinus edodes) regularly leads to symptoms... more Indoor cultivation of the edible mushroom Shii-take (Lentinus edodes) regularly leads to symptoms of mushroom worker's lung (MWL) in workers. An immunologic test is described allowing detection of IgG type antibodies against Shii-take spore antigens. It was found that MWL patients employed in Shii-take picking (n = 5) have significantly increased antibody titres against Shii-take spore antigens. Different control groups, viz, MWL patients employed in the cultivation of the white button mushroom Agaricus bisporus (n = 14) and of the oyster mushroom Pleurotus spp (n = 3), patients with Bechterew's syndrome (n = 7), sarcoidosis (n = 7), rheumatoid arthritis (n = 9), and healthy controls were found in the same range of low titres. The use of protective masks during picking reduced complaints of the workers (n = 14). However, their antibody titres increased with duration of employment despite the protection.

Research paper thumbnail of Ammonium deposition and the mycoflora in the rhizosphere of Douglas-fir

Soil Biology and Biochemistry, 1994

Ammonium deposition seems to be a major factor in the observed forest dieback in The Netherlands.... more Ammonium deposition seems to be a major factor in the observed forest dieback in The Netherlands. We studied the effects of ammonium sulphate (AS) on saprophytic fungi in the rhizosphere of Douglas-fir. In two Douglas-fir stands (Kootwijk and St Anthonis) with a different deposition rate of AS (ca 22 and 30 kgN ha-' yr-', respectively), fungi were isolated from the roots and identified. Canonical correspondence analysis (CCA) revealed that the fungal populations in the two stands differed significantly at the community level. Regression analysis showed that Trichoderma uiride and Penicillium spinulosum occurred significantly more frequently in the Kootwijk stand, whereas Cylindrocarpon didymum and Sesquicillium candelabrum were dominant species in the St Anthonis forest. P. brevicompactum appeared to be common in both Douglas-fir stands. To estimate the possible role of AS in the observed differences between the two stands, a laboratory experiment was performed in which 5, 50 and 200 kg N ha-' yr-' was applied to 3 yr old Douglas-firs for 23 months. Although the occurrence of Sesquicillium candelabrum, Trichoderma hamatum and T. viride increased and Sphaerodes retispora decreased with increasing ammonium deposition, CCA did not show that the overall fungal community was affected. The results of both CCA and regression analysis indicated that the differences between the two Douglas-fir stands were not primarily caused by different amounts of AS deposition. Separate analyses of the fungal communities of root tips and older roots showed that deposition of AS tended to alter the fungal community on the root tips; the occurrence of Sporothrix inpata was stimulated at increasing rates of AS, whereas the occurrence of 'unidentified chlamydospores' decreased.

Research paper thumbnail of Statistiek voor onderzoekers

Dit boek helpt onderzoekers statistiek toe te passen in hun onderzoek. Theoretisch (wiskundige) d... more Dit boek helpt onderzoekers statistiek toe te passen in hun onderzoek. Theoretisch (wiskundige) details zijn hierbij zoveel mogelijk achterwege gebleven. De in dit boek besproken methoden sluiten aan bij het onderzoek van Wageningen UR. De methoden worden toegelicht aan de hand van voorbeelden.

Research paper thumbnail of Odours of Plasmodium falciparum-infected participants influence mosquito-host interactions

Scientific reports, Jan 24, 2017

Malaria parasites are thought to influence mosquito attraction to human hosts, a phenomenon that ... more Malaria parasites are thought to influence mosquito attraction to human hosts, a phenomenon that may enhance parasite transmission. This is likely mediated by alterations in host odour because of its importance in mosquito host-searching behaviour. Here, we report that the human skin odour profile is affected by malaria infection. We compared the chemical composition and attractiveness to Anopheles coluzzii mosquitoes of skin odours from participants that were infected by Controlled Human Malaria Infection with Plasmodium falciparum. Skin odour composition differed between parasitologically negative and positive samples, with positive samples collected on average two days after parasites emerged from the liver into the blood, being associated with low densities of asexual parasites and the absence of gametocytes. We found a significant reduction in mosquito attraction to skin odour during infection for one experiment, but not in a second experiment, possibly due to differences in pa...

Research paper thumbnail of Feed the Crop or Feed the Soil? A Case Study in Leek (Allium Porrum L.)

Acta Horticulturae, 2010

The purpose of our study was to assess the role of soil quality parameters in leek production and... more The purpose of our study was to assess the role of soil quality parameters in leek production and to assess their importance relative to nitrogen (N) applied as fertilizer. We selected seven (2004) and seven (2005) fields on leek farms in the southern sand district of the Netherlands and measured physical and chemical soil properties. Three N rates (0, 90 and 360 kg N ha-1 as calcium ammonium nitrate; denoted as N 0 , N 90 , N 360) were given at each site. Leek (Allium porrum L. 'Kenton') was planted in June-July and harvested next spring. Measured response variables were shoot biomass yield (gross and net, fresh and dry) and shoot N-yield (gross, net) at harvest. Pooled data from both years were analyzed by linear regression. N uptake from unfertilized soil (U 0), and topsoil properties soluble organic N (N so), soil organic matter content (SOM), total nitrogen (N tot) and water content at field capacity (W fc) all had large and significant impacts on biomass yield and N yield. These five properties (X i) were correlated and were therefore used alternately in regression models. Effects of soil properties found by regression refer to a shift in the regressor from its 25% to its 75% percentile value, and are expressed here relative to mean yields (both years, all treatments). This normalization facilitates direct comparison with fertilizer effects. Normalized effects of X i variables on biomass yield and N yield were between +0.10 and +0.20. Effects of fertilizer application at N 90 were about +0.10 (biomass yield) and +0.20 (N yield). At N 360 effects were +0.10 to +0.20 (biomass yield) and +0.30 to +0.40 (N-yield). So while N fertilizer strongly promoted N-uptake relative to growth, soil properties X i affected growth and N yield more evenly. With shifts in X i variables, dry matter produced per kg additional N uptake was 1.49 to 1.77 times larger than with extra N uptake resulting from fertilizer application at N 90. This indicates that soil properties X i promoted yield not only via enhanced N supply. Besides effects of X i properties and N fertilizer, we found significant effects of year, soil texture, pH and inorganic soil N at planting, on biomass yield. Texture parameters F sfine (50-210 µm) and M 50 (median of particle size in 50-2000 µm fraction) had large and additive positive effects on net fresh yield. Apparent recovery of fertilizer N (ANR) averaged 0.35 at N 90 , and 0.17 at N 360. ANR decreased with higher N so and increased with higher W fc .

Research paper thumbnail of Discussie over het intercept in de relatie tussen Nminnitraat en de nitraatconcentratie in grondwater

Research paper thumbnail of Nitraat in het bodemprofiel als responsvariabele

Research paper thumbnail of Gegevensverzameling Sturen op nitraat; op zoek naar een indicator

Journal of Catalysis, 2003

In dit rapport worden de onderzoeksopzet en de bemonsteringsmethodieken van het project Sturen op... more In dit rapport worden de onderzoeksopzet en de bemonsteringsmethodieken van het project Sturen op nitraat beschreven. Het monitoringsysteem, de stratificering en de verdeling van proefplekken over de verschillende strata worden statistisch onderbouwd.Verder komen de bemonsterings- en meettechnieken aan bod die op proefplekniveau zijn gehanteerd. Hier worden zowel de metingen in het veld als de analyses in de laboratoria beschreven. In

Research paper thumbnail of Kiplekker, een kosten-batenanalyse van een reductie in de besmetting van pluimveevlees met salmonella en campylobacter

Het onderzoek tracht de kosten en baten van het Plan van Aanpak van het Productschap voor Vee, Vl... more Het onderzoek tracht de kosten en baten van het Plan van Aanpak van het Productschap voor Vee, Vlees en Eieren voor reductie van besmetting met salmonella en campylobacter voorzover mogelijk te kwantificeren aan de hand van een kosten-batenanalyse. Doel van het onderzoek is na te gaan of de maatschappelijke baten van het huidige beleid zich verhouden tot de kosten die met het beleid gemoeid gaan.

Research paper thumbnail of Pragmatische gevoeligheids- en onzekerheidsanalyse in het regionale waterbeheer

De komende jaren voert Waterschap Veluwe maatregelen uit ter voorkoming van wateroverlast. Om de ... more De komende jaren voert Waterschap Veluwe maatregelen uit ter voorkoming van wateroverlast. Om de eff ecten hiervan in het oppervlaktewatersysteem te bepalen, gebruikt het waterschap detailmodellen van haar watersysteem. Vanwege het ontbreken van meetgegevens is kalibratie beperkt mogelijk. Om die reden heeft de stochastische gevoeligheids-en onzekerheidsanalyse die het waterschap voor één stroomgebied uitvoerde, extra waarde. Met Monte Carlo-simulaties is op een pragmatische wijze inzichtelijk gemaakt welke parameters de grootste onzekerheid genereren in de maximale waterstand en het maximale debiet.

Research paper thumbnail of Sturen op nitraat: nitraatconcentraties in het grondwater en mogelijke indicatoren

Research paper thumbnail of Sturen op nitraat: waar zitten de knoppen?

Bemesting, beweiding en scheuren van grasland hebben een groot effect op de nitraatconcentratie i... more Bemesting, beweiding en scheuren van grasland hebben een groot effect op de nitraatconcentratie in het grondwater. Op maïsland heeft het achterwege laten van kunstmest, maar ook het achterwege laten van de bemesting van het vanggewas, behoorlijk effect. Dit blijkt uit een analyse van melkveebedrijven op zandgronden in het project Koeien & Kansen. De analyse omvat de effecten van bedrijfsvoering en van bodem, waterhuishouding en weer op de nitraatconcentratie

Research paper thumbnail of Deskstudie naar de mogelijkheden voor het aanwijzen van fosfaatarme gronden op basis van P-PAE

Het Bedrijfslaboratorium voor Grond- en Gewasonderzoek hanteert sinds twee jaar het onderzoekspak... more Het Bedrijfslaboratorium voor Grond- en Gewasonderzoek hanteert sinds twee jaar het onderzoekspakket Plant Available Elements (PAE). In dit pakket is fosfaat opgenomen (P-PAE). P-PAE is niet opgenomen in het protocol voor het aanwijzen van landbouwpercelen die in aanmerking komen voor een verhoogde fosfaatgebruiksnorm. Een deskstudie naar het opnemen van P-PAE als derde methode voor het aanwijzen van fosfaatarme gronden is uitgevoerd.

Research paper thumbnail of Predictive modeling of deoxynivalenol in winter wheat in The Netherlands

Research paper thumbnail of De betekenis van grondonderzoek met 0,01 M calciumchloride als basis voor het kaliumbemestingsadvies van bouwland

Research paper thumbnail of Grondonderzoek met 0.01 M CaCl2 als basis voor het kaliumbemestingsadvies van akkerbouwland. Herijking van de kaliumbemestingsadviezen

Research paper thumbnail of Nitrogen rate, surplus or residue? Performance of selected indicators for nitrate leaching

Research paper thumbnail of 1.3. 2 Gebruik van kwantitatieve TaqMan PCR in epidemiologisch onderzoek naar het optreden van aarfusarium in tarwe

Research paper thumbnail of Population dynamics in the belowground food webs in two different agricultural systems

Agriculture, Ecosystems & Environment, 1994

The biomass of 17 different groups of organisms was established every 6 weeks during 1 year in tw... more The biomass of 17 different groups of organisms was established every 6 weeks during 1 year in two arable fields cropped to winter wheat; one field was under conventional management (CONV) and the other under integrated management (INT). Bacteria showed the highest average biomass, followed by earthworms (INT only) and amoebae. Most of the groups of organisms had higher biomasses in INT than in CONV. The difference was statistically significant for protozoans, bacterivorous, fungivorous, and phytophagous nematodes and earthworms. Predatory Collembola, cryptostigmatic and bacterivorous mites, and enchytraeids showed a smaller biomass in INT than in CONV. The annual biomass production for each group was estimated using simulation model calculations. Bacteria showed the highest production followed by amoebae and earthworms (INT only). Most of the groups showed a higher biomass production in INT than in CONV. Exceptions were predatory and nematophagous mites, predatory and omnivorous Collembola, and enchytraeids. The total annual production was approximately 32 kg C ha-~ cm-~ depth in CONV and approximately 57 kg C in INT. The population dynamics were analysed by hierarchical cluster analysis. Four different clusters were found in CONV and INT. Bacteria, fungi, protozoans, bacterivorous nematodes and predatory mites showed the same trend in population dynamics in CONV and INT. All other groups showed different population dynamics in CONV and INT. This observation and the composition of these clusters suggested different conditions in CONV and INT.

Research paper thumbnail of Dynamics of microorganisms, microbivores and nitrogen mineralisation in winter wheat fields under conventional and integrated management

Agriculture, Ecosystems & Environment, 1994

To reduce environmental problems, integrated farming has been proposed, which may involve a consi... more To reduce environmental problems, integrated farming has been proposed, which may involve a considerable reduction of fertiliser-N input. A reduced fertiliser-N input must be compensated for by a higher N mineralisation from organic matter. To reduce losses and to facilitate optimal use of the N mineralised for crop growth, knowledge of the effects of management on soil organisms and on their role in N cycling is needed. Therefore, biomass and activity of bacteria, biomasses of fungi, bacterivorous amoebae, flagellates and nematodes, and in situ N mineralisation were monitored during a full year in a winter wheat field under conventional management (CONV) and integrated management (INT). Fungal biomass was about 100-fold lower than bacterial biomass. The average bacterial biomass was not significantly higher in INT than in CONV, whereas amoebae and nematodes were 64% and 22% higher, respectively. Average N mineralisation was 30% higher in INT. The differences are attributed to the approximately 30% higher organic matter content of INT. Bacterial biomass and frequency of dividing-divided cells (FDDC) were relatively low in December and January, probably owing to temperatures just above 0°C. At about 5°C in February and March, relatively high FDDC values and a doubling of bacteria occurred. During summer, FDDC values were relatively low and bacterial numbers were stable, probably owing to nutrient limitation. After harvest and skim ploughing, rapid increases in FDDC and bacteria were found. In the non-fumigated INT field, protozoan peaks coincided with the bacterial peak, whereas in CONV bacterivorous fauna were drastically reduced by soil fumigation. Nevertheless, the bacterial peaks were similar in CONV and INT, indicating that bacteria were not controlled by bacterivores. Nitrogen mineralisation was relatively low in winter. The increased bacterial growth in February and March, and in September appeared to enhance immobilisation rather than mineralisation of N. During the growing season from April to the end of August, bacterial growth was relatively low and N mineralisation was relatively high. This probably resulted from bacterivore feeding and from substrate-or nutrient-limited bacteria with a low growth

Research paper thumbnail of Mushroom Worker??s Lung

Journal of Occupational and Environmental Medicine, 1992

Indoor cultivation of the edible mushroom Shii-take (Lentinus edodes) regularly leads to symptoms... more Indoor cultivation of the edible mushroom Shii-take (Lentinus edodes) regularly leads to symptoms of mushroom worker's lung (MWL) in workers. An immunologic test is described allowing detection of IgG type antibodies against Shii-take spore antigens. It was found that MWL patients employed in Shii-take picking (n = 5) have significantly increased antibody titres against Shii-take spore antigens. Different control groups, viz, MWL patients employed in the cultivation of the white button mushroom Agaricus bisporus (n = 14) and of the oyster mushroom Pleurotus spp (n = 3), patients with Bechterew's syndrome (n = 7), sarcoidosis (n = 7), rheumatoid arthritis (n = 9), and healthy controls were found in the same range of low titres. The use of protective masks during picking reduced complaints of the workers (n = 14). However, their antibody titres increased with duration of employment despite the protection.

Research paper thumbnail of Ammonium deposition and the mycoflora in the rhizosphere of Douglas-fir

Soil Biology and Biochemistry, 1994

Ammonium deposition seems to be a major factor in the observed forest dieback in The Netherlands.... more Ammonium deposition seems to be a major factor in the observed forest dieback in The Netherlands. We studied the effects of ammonium sulphate (AS) on saprophytic fungi in the rhizosphere of Douglas-fir. In two Douglas-fir stands (Kootwijk and St Anthonis) with a different deposition rate of AS (ca 22 and 30 kgN ha-' yr-', respectively), fungi were isolated from the roots and identified. Canonical correspondence analysis (CCA) revealed that the fungal populations in the two stands differed significantly at the community level. Regression analysis showed that Trichoderma uiride and Penicillium spinulosum occurred significantly more frequently in the Kootwijk stand, whereas Cylindrocarpon didymum and Sesquicillium candelabrum were dominant species in the St Anthonis forest. P. brevicompactum appeared to be common in both Douglas-fir stands. To estimate the possible role of AS in the observed differences between the two stands, a laboratory experiment was performed in which 5, 50 and 200 kg N ha-' yr-' was applied to 3 yr old Douglas-firs for 23 months. Although the occurrence of Sesquicillium candelabrum, Trichoderma hamatum and T. viride increased and Sphaerodes retispora decreased with increasing ammonium deposition, CCA did not show that the overall fungal community was affected. The results of both CCA and regression analysis indicated that the differences between the two Douglas-fir stands were not primarily caused by different amounts of AS deposition. Separate analyses of the fungal communities of root tips and older roots showed that deposition of AS tended to alter the fungal community on the root tips; the occurrence of Sporothrix inpata was stimulated at increasing rates of AS, whereas the occurrence of 'unidentified chlamydospores' decreased.

Research paper thumbnail of Statistiek voor onderzoekers

Dit boek helpt onderzoekers statistiek toe te passen in hun onderzoek. Theoretisch (wiskundige) d... more Dit boek helpt onderzoekers statistiek toe te passen in hun onderzoek. Theoretisch (wiskundige) details zijn hierbij zoveel mogelijk achterwege gebleven. De in dit boek besproken methoden sluiten aan bij het onderzoek van Wageningen UR. De methoden worden toegelicht aan de hand van voorbeelden.

Research paper thumbnail of Odours of Plasmodium falciparum-infected participants influence mosquito-host interactions

Scientific reports, Jan 24, 2017

Malaria parasites are thought to influence mosquito attraction to human hosts, a phenomenon that ... more Malaria parasites are thought to influence mosquito attraction to human hosts, a phenomenon that may enhance parasite transmission. This is likely mediated by alterations in host odour because of its importance in mosquito host-searching behaviour. Here, we report that the human skin odour profile is affected by malaria infection. We compared the chemical composition and attractiveness to Anopheles coluzzii mosquitoes of skin odours from participants that were infected by Controlled Human Malaria Infection with Plasmodium falciparum. Skin odour composition differed between parasitologically negative and positive samples, with positive samples collected on average two days after parasites emerged from the liver into the blood, being associated with low densities of asexual parasites and the absence of gametocytes. We found a significant reduction in mosquito attraction to skin odour during infection for one experiment, but not in a second experiment, possibly due to differences in pa...

Research paper thumbnail of Feed the Crop or Feed the Soil? A Case Study in Leek (Allium Porrum L.)

Acta Horticulturae, 2010

The purpose of our study was to assess the role of soil quality parameters in leek production and... more The purpose of our study was to assess the role of soil quality parameters in leek production and to assess their importance relative to nitrogen (N) applied as fertilizer. We selected seven (2004) and seven (2005) fields on leek farms in the southern sand district of the Netherlands and measured physical and chemical soil properties. Three N rates (0, 90 and 360 kg N ha-1 as calcium ammonium nitrate; denoted as N 0 , N 90 , N 360) were given at each site. Leek (Allium porrum L. 'Kenton') was planted in June-July and harvested next spring. Measured response variables were shoot biomass yield (gross and net, fresh and dry) and shoot N-yield (gross, net) at harvest. Pooled data from both years were analyzed by linear regression. N uptake from unfertilized soil (U 0), and topsoil properties soluble organic N (N so), soil organic matter content (SOM), total nitrogen (N tot) and water content at field capacity (W fc) all had large and significant impacts on biomass yield and N yield. These five properties (X i) were correlated and were therefore used alternately in regression models. Effects of soil properties found by regression refer to a shift in the regressor from its 25% to its 75% percentile value, and are expressed here relative to mean yields (both years, all treatments). This normalization facilitates direct comparison with fertilizer effects. Normalized effects of X i variables on biomass yield and N yield were between +0.10 and +0.20. Effects of fertilizer application at N 90 were about +0.10 (biomass yield) and +0.20 (N yield). At N 360 effects were +0.10 to +0.20 (biomass yield) and +0.30 to +0.40 (N-yield). So while N fertilizer strongly promoted N-uptake relative to growth, soil properties X i affected growth and N yield more evenly. With shifts in X i variables, dry matter produced per kg additional N uptake was 1.49 to 1.77 times larger than with extra N uptake resulting from fertilizer application at N 90. This indicates that soil properties X i promoted yield not only via enhanced N supply. Besides effects of X i properties and N fertilizer, we found significant effects of year, soil texture, pH and inorganic soil N at planting, on biomass yield. Texture parameters F sfine (50-210 µm) and M 50 (median of particle size in 50-2000 µm fraction) had large and additive positive effects on net fresh yield. Apparent recovery of fertilizer N (ANR) averaged 0.35 at N 90 , and 0.17 at N 360. ANR decreased with higher N so and increased with higher W fc .

Research paper thumbnail of Discussie over het intercept in de relatie tussen Nminnitraat en de nitraatconcentratie in grondwater

Research paper thumbnail of Nitraat in het bodemprofiel als responsvariabele

Research paper thumbnail of Gegevensverzameling Sturen op nitraat; op zoek naar een indicator

Journal of Catalysis, 2003

In dit rapport worden de onderzoeksopzet en de bemonsteringsmethodieken van het project Sturen op... more In dit rapport worden de onderzoeksopzet en de bemonsteringsmethodieken van het project Sturen op nitraat beschreven. Het monitoringsysteem, de stratificering en de verdeling van proefplekken over de verschillende strata worden statistisch onderbouwd.Verder komen de bemonsterings- en meettechnieken aan bod die op proefplekniveau zijn gehanteerd. Hier worden zowel de metingen in het veld als de analyses in de laboratoria beschreven. In

Research paper thumbnail of Kiplekker, een kosten-batenanalyse van een reductie in de besmetting van pluimveevlees met salmonella en campylobacter

Het onderzoek tracht de kosten en baten van het Plan van Aanpak van het Productschap voor Vee, Vl... more Het onderzoek tracht de kosten en baten van het Plan van Aanpak van het Productschap voor Vee, Vlees en Eieren voor reductie van besmetting met salmonella en campylobacter voorzover mogelijk te kwantificeren aan de hand van een kosten-batenanalyse. Doel van het onderzoek is na te gaan of de maatschappelijke baten van het huidige beleid zich verhouden tot de kosten die met het beleid gemoeid gaan.