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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    Van bloem tot komkommer (interview met Jan Janse)
    Janse, J. - \ 2011
    Leeuwarder Courant (2011). - p. 8 - 8.
    Van bloem tot komkommer De verkoop van komkommers is ingezakt door de commotie over de darmbacterie Ehec. De komkommers móeten geoogst, er zit niets anders op. Het telen van komkommers is precisiewerk. Als de vruchten oogstrijp zijn, kun je ze niet zomaar een paar dagen langer laten zitten. ,,Dan worden ze te groot, en zijn ze niet meer te verkopen. Als de komkommers te zwaar worden, gaat dat bovendien ten koste van de kleine vruchtjes aan dezelfde plant. En dan heb je over een week geen productie'', zegt Jan Janse, gewasonderzoeker komkommer van de Wageningen UR Glastuinbouw. Ruim 200 van de ongeveer 290 Nederlandse telers van komkommers zagen hun afzet de afgelopen dagen volledig instorten. Normaal worden er in deze tijd wekelijks 30 miljoen komkommers uitgevoerd, vooral naar Duitsland. Ook al is er geen enkele aanwijzing of bewijs dat de Nederlandse komkommers iets te maken hebben met de darminfectie die in het noorden van Duitsland huishoudt, de Duitsers hebben even geen zin meer in onze calorie-arme, frisse en gezonde rauwkost. In Nederlandse supers gaan ze eveneens watminder snel over de toonbank. De komkommers aan de plant laten zitten, kan echter niet. ,,Er moet nu elke dag geoogst worden'', zegt Janse. Alle komkommers in Nederland worden onder glas geteeld. De meeste tuinders wisselen de planten drie keer per jaar. Ze zittennuin de tweede teelt. Eind juli, begin augustus begint de derde. De telers kopen het jonge goed van speciale bedrijven die de komkommerplant in drie weken tijd opkweken van zaadje tot plantje van 40 centimeter hoog. In de 3meter hoge kassenworden de jonge planten in substraat gezet, meestal steenwol. Een kubieke meter basalt levert 50 kuub steenwol. Daarop kunnen ongeveer een miljoen komkommers groeien. De steenwol wordt vervolgens weer verwerkt tot 8 kubieke meter baksteen, zegt Vincent Deenen van steenwolproducent Grodan. Als de planten van de eerste teelt zijn weggehaald, kun je dezelfde dag nog nieuwe planten zetten, aldus Janse. Dan duurt het nogwel even-somsal binnen drie weken - voor die plant vruchten geeft. Hijmoet eerst flink groeien, rondom een draad tot ongeveer 2 meter hoogte. Twee zijscheuten krijgen daar de ruimte om horizontaal door te groeien. Naast elke plant staat een druppelaar voor de voeding - bijvoorbeeld kalium en stikstof - en het water. Per vierkante meter oogst een teler zo'n 165 tot 200 komkommers per jaar. De vruchten groeien in de bladoksels van de plant. Bestuiving is niet nodig. Van bloem tot volwassen komkommer is een razendsnel proces. In de winter kan het drie weken duren, maar in deze tijd heb je al binnen een week een rijp product. Als hij 350 tot 400 gram weegt, moet je 'm afsnijden. Janse: ,,Naar een komkommer van 800 gram is geen vraag.''
    Herbage and animal production responses to fertilizer nitrogen in perennial ryegrass swards. II. rotational grazing and cutting
    Lantinga, E.A. ; Deenen, P.J.A.G. ; Keulen, H. van - \ 1999
    Netherlands Journal of Agricultural Science 47 (1999)3/4. - ISSN 0028-2928 - p. 243 - 261.
    The yield response of grass swards to fertilizer nitrogen (N) differs under cutting and grazing, as grazing cattle exert positive and negative effects on pasture production, with varying negative effects on different soil types. Nevertheless, current N fertilization recommendations in the Netherlands are based mainly on economic cost-benefit analyses of long-term cutting trials in small plots. To contribute to formulation of improved N fertilizer recommendations for grassland, experiments were carried out on two soil types and under different management regimes. The effect of fertilizer N application on grassland production and sward quality in perennial ryegrass swards was studied during a number of consecutive years under both rotational grazing and 4-weekly cutting. Experiment 1 was performed with dairy cows on a loam soil at 250 and 550 kg fertilizer N ha-1 yr-1. Experiment 2 was performed with beef cattle on a sand soil and fertilizer rates varying from 250 to 700 kg N ha-1 yr-1 under grazing and from 0 to 700 kg N ha-1 yr-1 under cutting. The results indicate that on loam, N had no effect on sward quality. In the second experimental year, total herbage yield under grazing was almost 10% higher than under cutting at 250 kg N ha-1 yr-1 due to recycling of N, whereas at 550 kg N ha-1 yr-1 the yield under grazing and cutting was the same. On sand, the economically optimum fertilizer application rate was on average 430 kg N ha-1 yr-1 for 4-weekly cutting. Under grazing and at whole system level (integrated grazing and mowing for silage), the optimum rate was below 250 kg N ha-1 yr-1. Under grazing on the sand soil, N aggravated sward deterioration due to treading, poaching and especially urine scorching. This was reflected in an increased absence frequency of rooted perennial ryegrass tillers in quadrats with an area of 1 dm2 at increasing fertilizer N application rates. It is concluded that current fertilizer N recommendations for grassland can be further refined by taking into account the positive and negative effects of grazing cattle, in dependence of soil type and level of N supply.
    Nitrogen use efficiency in intensive grassland farming
    Deenen, P.J.A.G. - \ 1994
    Agricultural University. Promotor(en): L. 't Mannetje; E.A. Lantinga. - S.l. : Deenen - ISBN 9789054852704 - 140
    graslanden - stikstof - grasslands - nitrogen

    This thesis describes the effects of fertilizer nitrogen on herbage yield under rotational and continuous grazing of perennial ryegrass swards with beef cattle and dairy cows, and under cutting only on both a sand and a silty loam soil. Furthermore effects are described of nitrogen input and grassland management on yield of perennial ryegrass swards after severe winters on both soils and the effects of dung and artificial urine on nitrogen uptake and herbage accumulation on a sand soil.

    Differences in both the apparent nitrogen recovery and the response of grassland production to fertilizer nitrogen applied could be related to treatment (cutting versus grazing), soil type (loam versus sand), length of the growing season, the amount of soil inorganic nitrogen in spring, sward quality and, in case of grazing, recycling of excretal nitrogen. The calculated economical optimum fertilizer application rate was on average 430 and 5 10 kg N ha -1yr -1for 4-weekly cutting on the sand soil and the loam soil, respectively. Under grazing and on a wholefarm scale (integrated grazing and mowing for silage) on the sand soil the optimum rate was some 200 kg ha -1less. Under grazing, especially on sand, nitrogen enhanced sward deterioration due to treading, poaching and especially urine scorching, leading to a loss of productivity. On loam, nitrogen had on average a much smaller deleterious effect. Tiller densities were highest under continuous grazing. Efficiency of use of ingested nitrogen varied from 23 to 31 % for dairy cows and was less than 10% for beef cattle at a fertilizer level of 250 kg N ha -1yr -1. Efficiency decreased with increasing N rates.

    Divergent relationships were found between the level of nitrogen input in the preceding year and spring herbage growth after a severe winter. Differences were only temporary. In case of a negative relationship, reductions in first cut dry matter yields were smaller in frequently defoliated (weekly cutting and continuous grazing) than in less frequently defoliated swards (4-weekly cutting and rotational grazing). Positive effects of urine and dung on nitrogen uptake and herbage growth on the sand soil were only observed in a low N sward (250 kg N ha -1yr -1) and were confined to 15 cm from the edge of the dung and urine patches.

    Herbage and animal production responses to fertilizer nitrogen in perennial ryegrass swards. 1. Continuous grazing and cutting.
    Deenen, P.J.A.G. ; Lantinga, E.A. - \ 1993
    Netherlands Journal of Agricultural Science 41 (1993). - ISSN 0028-2928 - p. 179 - 203.
    The effects of fertilizer N application on herbage intake and animal performance under continuous grazing management with dairy cows, and on herbage accumulation under a weekly and an approximately 4-weekly cutting regime were studied in 1986-1988 in resown Lolium perenne cv. Wendy grassland on a silty loam soil in Oostelijk Flevoland, Netherlands. 250-700 kg N/ha was applied annually under grazing and from 0 to 700 kg N/ha was applied under cutting. At an assumed marginal profitability of 7.5 kVEM per kg N applied the optimum N application rate was on average 511 and 308 kg/ha per year for 4-weekly cutting and continuous grazing, respectively (1 kVEM = 6.9 MJ Net Energy for lactation). However, especially under grazing, there was a great variation in response to N between years which could be related to soil N availability, length of the growing season and sward quality. Throughout the experimental period the mean tiller density in the grazed swards was hardly affected by the level of N application. However, there were temporary differences in openness of the sward which increased with the level of N application, leading to a loss of productivity as a result of impeded N uptake. Herbage N was poorly converted into animal products. The average efficiency of use of ingested N at 250 kg N was 23%. Higher rates of fertilizer N decreased N use efficiency (19% at 700 kg N/ha per year) but markedly increased N excreted per ha.
    Effect of cattle dung and urine on nitrogen uptake and yield of perennial ryegrass.
    Deenen, P.J.A.G. ; Middelkoop, N. - \ 1992
    Netherlands Journal of Agricultural Science 40 (1992). - ISSN 0028-2928 - p. 469 - 482.
    Distribution of excreted nitrogen by grazing cattle and its effects on sward quality, herbage production and utilization.
    Lantinga, E.A. ; Keuning, J.A. ; Groenwold, J. ; Deenen, P.J.A.G. - \ 1987
    In: Animal manure on grassland and fodder crops / v.d. Meer, H.G., Dordrecht : Martinus Nijhoff - p. 103 - 117.
    Phosphatidylcholine transfer protein: model for lipid-protein interactions and probe for membrane research
    Wirtz, K.W.A. ; Visser, A.J.W.G. ; Kamp, J.A.F. op den; Roelofsen, B. ; Deenen, L.L.M. van - \ 1985
    In: Recent advances in biological membrane studies: Structure and biogenesis, oxidation and energetics / Packer, L., - p. 29 - 43.
    Opslag van koolrabi in verschillende verpakkingen
    Damen, P.M.M. ; Hendriks, A. ; Deenen, H.P.M. - \ 1981
    Wageningen : Sprenger Instituut (Rapport / Sprenger Instituut no. 2164) - 3
    brassica oleracea var. gongylodes - koolrabi - nederland - opslag - kohlrabi - netherlands - storage
    Afkoelproeven met asperges in verschillende verpakkingen
    Damen, P.M.N. ; Hendriks, A. ; Deenen, H. - \ 1981
    Wageningen : Sprenger Instituut (Rapport / Sprenger Instituut no. 2175) - 3
    asparagus - koeling - koelen - voedselbewaring - voedingsmiddelen - groenten - chilling - cooling - food preservation - foods - vegetables
    Bloei en bloeislaging van de robusta koffie op Sumatra's Westkust
    Deenen, W.J. - \ 1936
    Wageningen University. Promotor(en): J.E. van der Stok. - Wageningen : Veenman - 120
    koffie - bloei - sumatra - nederlands indië - coffee - flowering - sumatra - netherlands east indies
    As an insight into flowering and fruit yield the percentage of flowers yielding fruits was estimated. To allow for variation between branches, many flowers must be taken. The extent of flowering of robusta coffee depended on the relation between vegetative and generative growth, both showing a maximum and a minimum, while factors favouring one were often adverse-for the other. The physiological condition of the trees strongly influenced fruit setting. Stephanoderes hampei F. may penetrate berries 3-5 months old. Consequently rotting and damage may lead to a considerable fall. This fall depended much on the condition of the tree and not on the number of S.hampei. Falling was also favoured by sunny and dry periods.
    A good regular shading promoted flowering and fruit production, due mainly to a better water supply preventing yellowing and dying of the leaves. Too much shading may be harmful to the generative growth, so pruning must lead to more light during wetter months. For a better water supply the humus content of the soil could be improved. The percentage fruit set of primary, secondary, upper, medium and low branches showed that 'topping', preventing water shortage in dry periods, was not harmful for fruit set. Lower trees also facilitate the control of S.hampei and the harvesting.
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