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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    Evaluatie Actieplan Stalbranden 2012-2016
    Bokma-Bakker, Martien ; Bokma, Sjoerd ; Ellen, Hilko ; Hagen, René ; Ruijven, Charlotte van - \ 2017
    Wageningen : Wageningen Livestock Research (Wageningen Livestock Research rapport 1035) - 80
    dierenwelzijn - dierlijke productie - diergezondheid - pluimvee - varkens - melkvee - schapen - geiten - paarden - stallen - brand - voorkomen van branden - veiligheid - animal welfare - animal production - animal health - poultry - pigs - dairy cattle - sheep - goats - horses - stalls - fire - fire prevention - safety
    Resilience of Amazonian forests : the roles of fire, flooding and climate
    Monteiro Flores, B. - \ 2016
    Wageningen University. Promotor(en): Marten Scheffer, co-promotor(en): Milena Holmgren Urba; Jose de Attayde. - Wageningen : Wageningen University - ISBN 9789462578876 - 128
    forests - resilience of nature - fire - flooding - floods - climate - floodplains - vegetation - amazonia - bossen - veerkracht van de natuur - brand - inundatie - overstromingen - klimaat - stroomvlakten - vegetatie - amazonia

    The Amazon has recently been portrayed as a resilient forest system based on quick recovery of biomass after human disturbance. Yet with climate change, the frequency of droughts and wildfires may increase, implying that parts of this massive forest may shift into a savanna state. Although the Amazon basin seems quite homogeneous, 14% is seasonally inundated. In my thesis I combine analyses of satellite data with field measurements and experiments to assess the role of floodplain ecosystems in shaping the resilience of Amazonian forests.

    First, I analyse tree cover distribution for the whole Amazon to reveal that savannas are relatively more common on floodplains. This suggests that compared to uplands, floodplains spend more time in the savanna state. Also, floodplain forests seem to have a tipping point at 1500 mm of annual rainfall in which forests may shift to savanna, whereas the tipping point for upland forests seems to be at 1000 mm of rainfall. Combining satellite and field measurements, I show that the higher frequency of savannas on floodplain ecosystems may be due to a higher sensitivity to fire. After a forest fire, floodplains lose more tree cover and soil fertility, and recover more slowly than uplands (chapter 2).

    In floodplains of the Negro river, I studied the recovery of blackwater forests after repeated fires, using field data on tree basal area, species richness, seed availability, and herbaceous cover. Results indicate that repeated fires may easily trap blackwater floodplains in an open-vegetation state, due the sudden loss of forest resilience after a second fire event (chapter 3).

    Analyses of the soil and tree composition of burnt floodplain forests, reveal that a first fire is the onset of the loss of soil fertility that intensifies while savanna trees dominate the tree community. A tree compositional shift happens within four decades, possibly accelerated by fast nutrient leaching. The rapid savannization of floodplain forests after fire implies that certain mechanisms such as environmental filtering may favor the recruitment of savanna trees over forest trees (chapter 4).

    In chapter 5, I experimentally tested in the field the roles of dispersal limitation, and environmental filtering for tree recruitment in burnt floodplain forests. I combine inventories of seed availability in burnt sites with experiments using planted seeds and seedlings of six floodplain tree species. Repeated fires strongly reduce the availability of tree seeds, yet planted trees thrive despite degraded soils and high herbaceous cover. Moreover, degraded soils on twice burnt sites seem to limit the growth of most pioneer trees, but not of savanna trees with deeper roots. Our results suggest a limitation of forest trees to disperse into open burnt sites.

    The combined evidence presented in this thesis support the hypothesis that Amazonian forests on floodplains are less resilient than forests on uplands, and more likely to shift into a savanna state. The lower ability of floodplains to retain soil fertility and recover forest structure after fire, may accelerate the transition to savanna. I also present some evidence of dispersal limitation of floodplain forest trees. Broad-scale analyses of tree cover as a function of rainfall suggest that savannas are likely to expand first in floodplains if Amazonian climate becomes drier. Savanna expansion through floodplain ecosystems to the core of the Amazon may spread fragility from an unsuspected place.

    Stalbranden. Impact, oorzaken en preventie.
    Hopster, Hans - \ 2012
    animal housing - stalls - fire - fire prevention - fire management - animal welfare - veterinarians - animal health - animal production
    Soil organic matter dynamics in a Cerrado Oxisol
    Roscoe, R. - \ 2002
    Wageningen University. Promotor(en): N. van Breemen; P. Buurman. - S.l. : S.n. - ISBN 9789058085627 - 156
    organisch bodemmateriaal - grondbewerking - brand - cerradogronden - koolstof - landgebruik - brazilië - soil organic matter - tillage - fire - cerrado soils - carbon - land use - brazil
    The Brazilian Cerrado is the second largest biome in the country, spreading over 23 % of the national territory. In the last three decades, it has increasingly contributed to the national production, being responsible in 1995 for 25% of the national agricultural production and sheltering 40% of the cattle flock. Development strategies have stimulated strongly mechanised and intensive agricultural practices, which has raised concerns about soil organic matter (SOM) losses and soil degradation.

    Cerrado soils are dominated by low-activity clays and are characterised by high acidity and low pH, cation exchange capacity (CEC), and available nutrients (especially P and N). SOM exerts important functions in these soils, which are closely related to soil quality and sustainability. It is responsible for most of the CEC, and is involved in process of soil aggregation and water dynamics. Losses of SOM due to cultivation may seriously affect these functions, and also represent an important source of CO 2 to the atmosphere. Studying the effects of different management systems on C dynamics in Cerrado soils may help to develop better ways of using these ecosystems.

    The initial objective of this thesis was to evaluate the impact of different management systems on SOM dynamics in one of the most representative soil classes in Cerrado, the Dark Red Latosol (18% of the total area; Oxisol - Soil Taxonomy; Ferrasol - FAO Legend). The research strategy adopted was to compare, in the same soil unit, paired plots with different management systems (native vegetation, pasture, no-tillage and conventional tillage). The Dark Red Latosol unit (Typic Haplustox) was located in the experimental research institution of EMBRAPA-CNPMS (Brazilian Institute of Agricultural Research - Maize and Sorghum National Research Centre), in Sete Lagoas - MG, Brazil. To assess SOM dynamics, a combination of two methodologies was proposed, (i) the physical fractionation of soil in particle-size and density separates, and (ii) replacement calculations using the natural abundance of the 13C isotope. The physical fractionation aimed at separating SOM pools with different chemistry, location, and turnover, which hypothetically would be more sensitive to soil alterations than total SOM. The natural abundance of 13C was proposed to assess the turnover time of SOM and its fractions. However, as very little data was available about the use of these methodologies in Cerrado ecosystems, the initial focus of the thesis was changed. The initial general objective was extended to three specific objectives:

    (i) to adapt the methodologies of physical fractionation of soil and 13C natural abundance to SOM studies in a Cerrado ecosystem;

    (ii) to contribute to a better understanding of the distribution and dynamics of different SOM pools in this specific environment; and

    (iii) to evaluate the long-term effect on SOM of converting a cerrado sensu stricto into cultivated pasture or to annual crops (maize and beans) under conventional tillage and no-tillage.

    In Chapter 2, an exploratory study was conducted to establish ad13C-reference profile under the native cerrado sensu stricto . In a native reserve located at EMBRAPA-CNPMS, three soil profiles were analysed in plots with different fire history. Results showed that the studied cerrado was a C 3 -dominated vegetation, presentingd13C values typical for soils under such a vegetation throughout the soil profile. Fire favoured the grass population and increased the amount of C 4 -derived carbon in the system. No alteration in carbon stocks in soils was observed with increasing fire incidence. It was concluded that different fire regimes may interfere with the establishment of a 13C standard profile for dynamic studies. The profiles under low fire intensity were considered a good reference for the further studies.

    In Chapter 3, the focus was on establishing a physical fractionation procedure for SOM in the Cerrado Oxisol under investigation. Special attention was given to the dispersion by ultrasonic energy, a crucial point in the methodology. A procedure to calibrate the ultrasonic equipment and to determinate the minimum of energy required for an efficient dispersion is proposed. Increasing ultrasonic energy significantly changed the amounts of C and N, the C:N ratio, and thed13C values of the particle size fractions analysed (0-2mm; 2-50mm; 50-100mm; 100-250mm; 250-2000mm). The results suggest that the soil (< 2 mm) can be divided into unstable (100-2000mm) and stable (50-100mm) aggregates. A threshold energy of 260-275 J ml -1is proposed for the dispersion of unstable aggregates. The use of this threshold energy, combined with particle-size fractionation, was not satisfactory for all purposes, since litter-like material and relatively recalcitrant organic carbon present in stable aggregates > 100mm were recovered in the same pool. An ultrasonic energy of 825 J ml -1was not sufficient to stabilize the redistribution of soil mass and organic matter among particle-size fractions, but at energies above 260-275 J ml -1relatively stable aggregates would fall apart and cause a mix of carbon with varied nature in the clay fraction.

    In order to better understand the dynamics of soil organic matter (SOM) in Oxisols, and the impact of converting the cerrado sensu stricto into pasture, the dynamics of physically separated SOM pools at different depths in a cerrado Oxisol (Typic Haplustox), under natural conditions and after 23 years of cultivated pasture ( Brachiariaspp . ) was studied via the replacement of the native C (C 3 -derived) by pasture C (C 4 -derived) (Chapter 4). Organic C stocks of the original cerrado (15±3 kg m -2) and pasture (17±3 kg m -2) were not significantly different, which was attributed to the high biomass production of the tropical grasses and the protective effect of the high clay content (> 800g kg -1). The clay + silt fraction accumulated 89-91% of the total organic C. The replacement of cerrado-derived C by pasture-derived C was in average 36%, 34%, and 19% for A p , AB 1 , and B w2 horizons respectively, suggesting a fast turnover rate of organic C, regardless of the high clay content. The replacement decreased in the order: free low-density organic matter (LDOM) > heavy fractions (sand, silt, clay) > occluded-LDOM. The lower replacement of the occluded-LDOM compared to the heavy fractions was attributed to protection inside aggregates and to a possible accumulation of C 3 -derived charcoal (black carbon) in that fraction. After 23 years of pasture, about 50% of the total organic C in the free-LDOM in the topsoil was still from cerrado, indicating that a significant part of this fraction was relatively recalcitrant. Charcoal fragments observed in the fraction suggested that the recalcitrance was probably due to charred material.

    In Chapter 5, the spatial continuity ofd13C and other soil organic matter (SOM) related variables (organic C, total N, and C:N ratio) were analysed in the native cerrado sensu stricto and in a nearby cultivated area with neighbouring plots under conventional and no-tillage systems. The aims were to describe the spatial variability of these properties in the cerrado, with especial attention to fire effects, and to analyse how management systems affect their spatial structure. Global, within strata, and stratified kriging were used to model the spatial variability in the areas. In cerrado, the total variability of all variables was relatively small, which was attributed to the high textural and mineralogical homogeneity of the clayey soil. Nevertheless, part of the variability was spatially structured. In cerrado locations with more open vegetation, long-term cumulative effect of repeated fires seemed to determine the spatial structure ofd13C and SOM-related variables. Cultivation reduced the variability of most of the variables and changed their spatial structure. The variables tended to be less spatially structured in no-tillage than in conventional tillage, due to small-scale variability. The spatial structure observed ford13C in the cultivated area was probably inherited from the former cerrado vegetation. This implies that, in studies of SOM dynamics, the variability of the replacements would be overestimated if the trends in both areas were not taken into account.

    In Chapter 6, as the different particle-size fraction in Chapter 4 presented similar dynamics, only density fractionation was used to assess changes in SOM upon 30 years of cultivation. The objectives of the study were (i) to evaluate the long-term impact of conventional and no-tillage systems on SOM stocks in the soil, and (ii) to better understand the dynamics of SOM in different density fractions of this soil. It was observed that cultivation led to compaction, significantly increasing soil bulk density. This resulted in a systematic overestimate of C and N stocks in cultivated areas when compared to the natural cerrado. Conversion of cerrado into conventional tillage (CT) or no-tillage (NT) system did not alter the total C (~100 Mg ha -1) and N (~7 Mg ha -1) stocks of the first 45cm depth in 30 years of cultivation. However, about 22% of the total carbon was replaced by maize material in this period. In accordance with results from Chapter 4, the relative replacement of carbon decreased the order: free light fraction (F-LF) > heavy fraction (HF) > occluded light fraction (O-LF). The low substitution in the O-LF was attributed to the possible presence of charcoal. The F-LF showed the highest sensitivity to changes in management system, and converting cerrado into cropland significantly decreased its quantity. The proportion of C replacement in this fraction was higher in CT than NT, suggesting a faster turnover in the first. Nevertheless, because most carbon (~95%) was held in the HF, carbon dynamics in the whole soil was controlled by the behaviour of this fraction.

    In Chapter 7, results form Chapter 4 and Chapter 6 were used to calculate proportions and stocks of carbon derived from a newly introduced C 4 vegetation in a C 3 ecosystem, by two different linear mixing models. One model assumed no 13C discrimination upon humification for the new introduced C 4 material, and the other assumed equal 13C discrimination for both C 3 and C 4 materials. The aims were to evaluate (i) how the assumption of equal 13C discrimination for C 3 and C 4 material may affect estimates of proportions and stocks of C 4 -derived carbon for different soil depths and soil organic matter fractions; (ii) the significance of a possible difference between outputs using the different models; and (iii) the sensitivity of this difference to variations in input parameters. The assumption of equal discrimination was discussed in the light of the current theoretical understanding of processes leading to 13C discrimination in soils. Taylor series approximation was applied to estimate the output uncertainties of the models. Sensitivity analysis was used to test the influence of these outputs in the magnitude of 13C discrimination with decomposition for the standard C 3 vegetation, the population standard deviation of soil and litterd13C, and the sample size for soil and litter. The two models may generate significantly discrepant outputs. This difference was most sensitive to the standard deviation of the soild13C population and the number of soil samples. A critical analysis of the current understanding of processes leading to 13C discrimination in soils suggests that the assumption of absence of 13C discrimination for the newly C 4 introduced material would provide the most realistic results.

    Carbon stocks in the studied soil did not change with land-use (pasture, conventional tillage, and no-tillage). The low capacity of occlusion in soil aggregates and their high stability, as well as the massive concentration of SOM in the heavy fraction (largely dominated by clay-sized organo-mineral complexes) explained the relative resilience of this soil upon disturbance. These characteristics were probably related to the large contents of oxi-hydroxides of Fe and Al in the studied soil. Nevertheless, a significant amount of SOM (about 1/4 to 1/3) was replaced in 30 years, suggesting that large part of the carbon is rather active. Conversely, the remaining 2/3 to 3/4 seemed to be fairly stable, since it was not recycled even after 30 years of intensive cultivation. This fraction probably represents the passive compartment used in dynamic models such as CENTURY and RothC.

    In the studied Oxisol, density fractionation separated SOM fractions with contrasting dynamics. This could potentially be used for separating measurable SOM pools, which would represent an important advance in the verification of current carbon dynamic models. However, these fractions were a mixture of labile and recalcitrant components, and procedures for distinguishing these components are needed. Quantification of charcoal in the light fraction and non-hydrolysable materials in the heavy fractions represents a promising alternative.

    The 13C natural abundance approach proved efficient for tracing SOM dynamics in the Cerrado Oxisol. The spatial variability ofd13C in different plots (e.g. cerrado vs. pasture or cultivated plots) is responsible for most of the final uncertainty in replacement calculations. To reduce such an uncertainty, samples should be taken at the same locations before and after conversion for a new vegetation. This implies that, ideally, experiments should be planed for long-term evaluation in the same area, instead of comparing neighbouring plots.

    The assumptions in the calculations can significantly affect the outputs (e.g. source proportions). When a C 4 plant is introduced into a C 3 ecosystem, the assumption of no fractionation for the newly introduced material seems the most reliable option. Nevertheless, further research is needed to better understand the process of isotope fractionation during decomposition.

    Einfluss mehrmaliger Belastungen auf Schwarzfleckigkeit bei Speisekartoffeln
    Molema, G.J. ; Verwijs, B.R. ; Bosma, A.H. - \ 1998
    Der Kartoffelbau 49 (1998)1/2. - ISSN 0022-9156 - p. 20 - 23.
    afwijkingen, planten - solanum tuberosum - aardappelen - oogstschade - fysische bodemeigenschappen - intern transport op landbouwbedrijven - mechanische schade - brand - plant disorders - solanum tuberosum - potatoes - crop damage - soil physical properties - intrafarm transport - mechanical damage - fire
    Onderzoek naar het ontstaan van stootblauw bij aardappelen
    Fysiologische en biochemische regulatie van de vorming van stootblauw bij aardappel
    Stevens, L.H. ; Davelaar, E. ; Haverkort, A.J. ; Helsper, J.P.F.G. ; Uenk, D. - \ 1998
    Wageningen : AB-DLO - 109
    plantenziektekunde - bewaarziekten - solanum tuberosum - aardappelen - oogstschade - mechanische schade - brand - plant pathology - storage disorders - solanum tuberosum - potatoes - crop damage - mechanical damage - fire
    Soil acidification effects on fine root growth of Douglas-fir on sandy soils
    Olsthoorn, A.F.M. - \ 1998
    Agricultural University. Promotor(en): R. Rabbinge; W.G. Keltjens; G.M.J. Mohren. - Wageningen : IBN-DLO - ISBN 9789076095059 - 153
    bosbouw - brand - verontreiniging - bomen - zandgronden - verzuring - bodem ph - bodemaciditeit - plantenfysiologie - plantenontwikkeling - wortels - nederland - pseudotsuga menziesii - forestry - fire - pollution - trees - sandy soils - acidification - soil ph - soil acidity - plant physiology - plant development - roots - netherlands - pseudotsuga menziesii

    The ammonium sulphate deposited in forest ecosystems in the Netherlands as a result of air pollution currently exceeds 80 kg N ha -1yr -1locally. To study the influence of this air pollution on fine root density and its dynamics, fine root growth was monitored for three years in two young mature stands of Douglas-fir on sandy soils in the central part of the Netherlands in the ACIFORN project (ACIdification of FORests in the Netherlands). In the drier site the fine root density in early summer was higher and more strongly reduced after a dry spring than at the more favourable site. The fine root density appeared to depend on the proximity of the tree stems in the stand. In normal years, the main peak of fine root growth occurred in spring, with less growth during summer. After a dry spring, fine root growth on the drier site reacted strongly to periods with rain in summer. In a greenhouse trial with one-year-old seedlings of Douglas-fir in sand, ammonium sulphate was added to simulate the present acidic deposition. Part of the ammonium was nitrified into nitrate. This resulted in different ammonium, nitrate, aluminium levels and pH in the different treatments. In the treatments with the highest applications, fine root length was reduced by 50 % compared to the control, and the specific root length was reduced by 40 %.

    A critical review of the results reported in the literature, to ascertain the total effect of the soil chemical changes since the start of the industrial revolution on the fine root density, revealed that aluminium is the main factor reducing fine root growth, even at sub-lethal concentrations in the soil solution. The fine root length is probably reduced by 50 % in the topsoil, and by 75 % in the subsoil. Excessive nitrogen availability reduces the total fine root biomass by 30 %. The net result is that the fine root system is less dense and more shallow than it would be without acidic deposition. This reduces the potential for water uptake on coarse sandy soils, and increases fine root mortality in long dry periods, especially on poor sites. An elementary model to describe fluctuations in the fine root density during and after a drought is used to illustrate the effects of soil acidification and nitrogen enrichment on drought susceptibility. Accumulated deposition has enhanced the risks of tree mortality or forest dieback induced by severe drought.

    Effecten van mechanische stress tijdens transport op de houdbaarheid van potplanten
    Slootweg, G. ; Bulle, A.A.E. - \ 1996
    Aalsmeer : PGB (Rapport / Proefstation voor Bloemisterij en Glasgroente 60)
    oogstschade - brand - mechanische schade - nederland - plantaardige producten - potplanten - onderzoek - behandeling - binnen kweken (van planten) - crop damage - fire - mechanical damage - netherlands - plant products - pot plants - research - treatment - indoor culture
    Stootblauw in de keten van tafelaardappelen
    Molema, G.J. ; Berg, J.V. van de; Bouman, A. ; Klooster, J.J. ; Verwijs, B.R. - \ 1995
    Wageningen : IMAG-DLO - ISBN 9789054061311 - 43
    solanum tuberosum - aardappelen - aardappelopslagplaatsen - oogstschade - mechanische schade - brand - intern transport op landbouwbedrijven - solanum tuberosum - potatoes - potato stores - crop damage - mechanical damage - fire - intrafarm transport
    Bestrijding tarwe-opslag in veldbeemd met twee typen onkruidbranders
    Baltus, P.C.W. - \ 1994
    In: Jaarboek 1993-1996 : verslagen van afgesloten onderzoeksprojecten op de regionale onderzoekcentra en het PAGV. Akkerbouw Lelystad : Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond [etc.] (Publikatie / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond, Regionale Onderzoekcentra No. 70a-81A) - p. 134 - 136.
    verbranden - gecontroleerd branden - brand - vlammenspuiten - hexaploïdie - gewasbescherming - Poa - Triticum aestivum - tarwe - burning - controlled burning - fire - flame cultivators - hexaploidy - plant protection - Poa - Triticum aestivum - wheat
    Biochemische factoren die een mogelijke rol spelen bij het ontstaan van stootblauw bij aardappel (Solanum tuberosum L.)
    Stevens, L.H. - \ 1994
    Wageningen : AB-DLO (Rapport / AB-DLO 27) - 29
    oogstschade - brand - mechanische schade - plantenziektekunde - aardappelen - solanum tuberosum - bewaarziekten - crop damage - fire - mechanical damage - plant pathology - potatoes - solanum tuberosum - storage disorders
    Zodebemesting op gras-klavermengsels; het ,,snij-effect'
    Schils, R.L.M. ; Sikkema, K. - \ 1992
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 5 (1992)1. - ISSN 0921-8874 - p. 1 - 3.
    dierlijke meststoffen - klavers - oogstschade - kunstmeststoffen - brand - graslanden - injectie - mechanische schade - drijfmest - bodeminjecteurs - trifolium - animal manures - clovers - crop damage - fertilizers - fire - grasslands - injection - mechanical damage - slurries - soil injectors - trifolium
    Het is mogelijk dat het aandeel witte klaver hierdoor beonvloed wordt. Dit artikel gaat vooral over dat tweede aspect, het zogenaamde snij-effect van zodebemesting.
    Invloed van berijden op produktie en persistentie van grassoorten = Effect of driving on yield and persistence of grass species
    Luten, W. ; Roozeboom, L. ; Remmelink, G.J. - \ 1983
    Lelystad : Proefstation voor de Rundveehouderij, Schapenhouderij enPaardenhouderij (Rapport / Proefstation voor de Rundveehouderij, Schapenhouderij en Paardenhouderij P.R. 90) - 18
    oogstschade - brand - graslanden - mechanische schade - bodemverdichting - oogsttoename - oogstverliezen - opbrengsten - voedergrassen - machines - crop damage - fire - grasslands - mechanical damage - soil compaction - yield increases - yield losses - yields - fodder grasses - machines
    Vergelijkende proef waarbij gedurende 3 jaren ('74-'76) is nagegaan in hoeverre de produktie en persistentie van verschillende soorten rassen en typen van gras door berijden na de oogst beinvloed wordt. De drogestofopbrengst werd na berijden van de graszode duidelijk nadelig beinvloed
    Mechanical damage to potatoes
    Hessen, J.C. ; Kroesbergen, E. - \ 1960
    Wageningen : [s.n.] (Publikatie / Instituut voor bewaring en verwerking van landbouwprodukten 34)
    oogstschade - brand - mechanische schade - aardappelen - solanum tuberosum - crop damage - fire - mechanical damage - potatoes - solanum tuberosum
    De toepassing van gedeelde stikstofgiften bij enkele zaadgewassen
    Roon, E. van - \ 1959
    Wageningen University. Promotor(en): A.C. Schuffelen. - Wageningen : Ponsen & Looijen - 131
    stikstofmeststoffen - oogstschade - mechanische schade - brand - bijproducten - stengels - vezels - stro - nitrogen fertilizers - crop damage - mechanical damage - fire - byproducts - stems - fibres - straw
    The influence was studied of split dressings of N on susceptibility to lodging, on yields of grain and straw and on seed quality of a number of seed crops: poppy (Papaver somniferum), spinach (Spinacia oleracea), radish (Raphanus sativus), caraway (Carum carvi), winter swede-like oilrape (Brassica napus var. biennis) and canary grass (Phalaris canariensis). The data on yield, lodging and quality were from field trials under normal management. The second application of N was just before flowering. Of the 6 seed crops, at least 3 (poppy, spinach, radish and sometimes caraway) increased in seed production. The other crops reacted either indifferently (caraway, winter swede-like oilrape) or always negatively (canary grass). Split dressings improved seed quality of poppy and radish. The commercial value of other crops was not affected. The effect on straw stiffness (lodging) of the crops concerned was not marked; only for poppy and to a lesser extent spinach and radish did split application provide some advantage. For poppy, spinach and radish seed N dressing could be delayed until plants were in full bloom.
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