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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    Does the informal seed system threaten maize seed health?
    Biemond, P.C. ; Oguntade, O. ; Stomph, T.J. ; Termorshuizen, A.J. ; Struik, P.C. - \ 2013
    In: 10th International Congress of Plant Pathology: Bio-security, food safety and plant pathology, August 25-30, 2013, Beijing, China. - - p. 246 - 247.
    seed-producing farmers, the informal Seed System, despite the presence of seed companies selling hybrid maize seed. Overhead costs force seed companies to charge a relatively high seed price, while farmers have limited budget for seed, request small quantities, and live in remote areas far from seed company outlets. The informal SS can meet this seed demand, but seed quality remains unknown. The objective of this research was to test seed quality (germination, off-types and seed health) of 87 farmer-produced seed samples from Northern Nigeria, and to compare it with six seed company and six foundation seed samples. Seed health was quantified by plating disinfected seeds onto agar, and identifying all bacteria and fungi present after three days. The most prevalent seed-borne pathogen was Fusarium verticillioides, identified in all samples and infecting over 50% of the 49.500 seeds tested. Twelve seed-borne pathogens were identified. Bipolaris maydis (found in 45% of the farmer-produced samples), Botryodiplodia theobromae (97%), Curvularia lunata (38%), and Macrophomina phaseolina (74%) were the four most devastating pathogens detected. Seed company samples had lower infection incidences than farmer produced seed for three out of four of these pathogens, and had significantly less off-types (P
    Can seed systems contribute to mycotoxin control?
    Biemond, P.C. ; Stomph, T.J. ; Lava Kumar, P. ; Struik, P.C. - \ 2013
    In: 10th International Congress of Plant Pathology: Bio-security, food safety and plant pathology, 25-30 August 2013, Beijning, China. - - p. 363 - 363.
    Mycotoxins, toxins produced by fungi, are threatening millions of people in developing countries. Consumption of mycotoxin-contaminated maize can cause cancer and even sudden death. Infection with mycotoxigenic fungi is required for mycotoxin production to occur. Infection can take place by seed-to-seedling transmission when seeds are infected. Seed samples are often heavily infected with mycotoxigenic fungi. We carried out a risk analysis of infection with mycotoxigenic fungi in formal and informal seed systems. A schematic overview of the maize value chain is presented to identify key risks and opportunities in the formal and informal seed system. A range of potential control measurements is discussed based on criteria for effective and sustainable control. Finally, an integrated approach is recommended based on control measures in the seed system.
    Health of farmer-saved maize seed in north-east Nigeria
    Biemond, P.C. ; Oguntade, O. ; Stomph, T.J. ; Lava Kumar, P. ; Termorshuizen, A.J. ; Struik, P.C. - \ 2013
    European Journal of Plant Pathology 137 (2013)3. - ISSN 0929-1873 - p. 563 - 572.
    macrophomina-phaseolina - fusarium-verticillioides - charcoal rot - population - biocontrol - drought - cowpea - system
    Many Nigerian farmers depend for their seed on seed-producing farmers, the so-called informal Seed System (SS), but seed quality of the SS is unknown. Farmers planting low quality seed risk poor field emergence and low plant vigour as a result of low physiological quality or infection with seed-borne pathogens. The objective of this research was to test seed quality of maize seed from the informal SS in north-east Nigeria. A total of 46,500 seeds (93 samples of 500 seeds each) were tested for germination, off-types and seed health. Seed pathology was quantified by plating disinfected seeds onto agar, and identifying the fungi present after 3 days incubation. Twelve seed-borne pathogens were identified including Bipolaris maydis (found in 45 % of the farmer-produced samples), Botryodiplodia theobromae (97 %) and Curvularia lunata (38 %). All samples were infected with Fusarium verticillioides, with a median infection incidence of 59 % (2009) and 51 % (2010). None of the 93 samples tested passed the demands for certified seed of the National Agricultural Seeds Council (NASC) in Nigeria, in particular the maximum limit of five off-types per kg seed sample. Based on these results, seed-producing farmers must improve the health of seed. The NASC should revise the standards for off-type seeds to minimize the time spent by farmers sorting planting material.
    Seed quality in informal seed systems
    Biemond, P.C. - \ 2013
    Wageningen University. Promotor(en): Paul Struik, co-promotor(en): Tjeerd-Jan Stomph. - S.l. : s.n. - ISBN 9789461736420 - 120
    zaadkwaliteit - zaadfysiologie - vigna unguiculata - vignabonen - zaadkieming - zaadpathologie - mycotoxinen - zea mays - nigeria - seed quality - seed physiology - vigna unguiculata - cowpeas - seed germination - seed pathology - mycotoxins - zea mays - nigeria

    Keywords: informal seed systems, seed recycling, seed quality, germination, seed pathology, seed health, seed-borne diseases, mycotoxigenic fungi, Fusarium verticillioides, mycotoxins, Vigna unguiculata, Zea mays, Nigeria.

    Seed is a crucial input for agricultural production. Approximately 80% of the smallholder farmers in Africa depend for their seed on the informal seed system, consisting of farmers involved in selection, production and dissemination of seed. The lack of overhead, distribution and seed testing costs enables seed-producing farmers to offer seed for low prices, but seed quality is not always good. Seed-producing farmers multiply their seed on-farm without frequent seed renewal, referred to as seed recycling, which may lead to low seed quality. This research analysed the effect of seed recycling on physiological quality and seed health of cowpea and maize, and compared seed quality of the formal and informal seed system.

    We tested the physical and physiological quality of cowpea seeds produced by the formal and informal seed system. Five out of six foundation seed samples, 79 out of 81 samples of farmers’ seed, and six out of six seed company samples failed to meet standards for foundation and certified seeds of the National Agriculture Seed Council (NASC), the seed industry regulatory agency in Nigeria. No evidence was found for a negative effect of seed recycling on physiological quality of cowpea seeds. We analysed 45,500 cowpea seeds for seed-borne bacteria and fungi to compare the performance of formal and informal seed systems. All samples were heavily infected with seed-borne pathogens, including Fusarium oxysporum (69% of the samples) and Macrophomina phaseolina (76%). No evidence was found that seed recycling in the informal seed system did lead to increased levels of seed-borne pathogens. We also analysed seed quality of farmer-produced maize seed to compare it with the formal seed system. The seed company samples had significantly higher germination (99.3%) than farmer-produced seed (97.7%), but not a single sample passed the requirements for certified seed of the NASC. Twelve seed-borne pathogens were identified including Bipolaris maydis (found in 45% of the farmer-produced samples), Botryodiplodia theobromae (97%) and Fusarium verticillioides (100%). Seed recycling had no negative effect on the physiological quality or seed health of maize seed. We analysed formal and informal seed systems to assess the opportunities to prevent mycotoxigenic fungi infection in maize seeds. A range of control methods to avoid fungal infection and mycotoxin production is discussed in relation to three criteria for sustainable implementation in developing countries. An integrated approach is recommended, with special attention towards the local seed system. As an overall conclusion of the work it can be stated that the informal seed system did not underperform compared to the formal seed system for cowpea, but did underperform in relation to seed company samples of maize. There was no evidence that seed recycling reduces seed quality of cowpea and maize seed samples, so frequent seed renewal will not improve seed quality of the informal seed system. We recommend a new quality assurance system for the informal seed system based on seed quality testing by farmers themselves, without interference by government or external laboratories. Farmers publish their seed testing results on the bag, while buyers can retest the seed to verify the quality. Further research is required to develop and implement this system in different countries, agro-ecologies and crops, and to develop methods that enable farmers to test seed health quality themselves.

    Does the informal seed system threaten cowpea seed health?
    Biemond, P.C. ; Oguntade, O. ; Lava Kumar, P. ; Stomph, T.J. ; Termorshuizen, A.J. ; Struik, P.C. - \ 2013
    Crop Protection 43 (2013). - ISSN 0261-2194 - p. 166 - 174.
    nigeria
    Most smallholder farmers in developing countries depend on an informal Seed System (SS) for their seed. The informal SS is often criticized because farmer-produced seed samples are not tested for seed health, thus accepting the risk of planting infected seeds. Here we aimed at assessing the quality of seeds acquired from the informal SS, and compared this with the quality of seeds obtained from the formal SS. Cowpea seed production in northern Nigeria was used as a case study to evaluate the seed health of samples from farmers, seed companies, and foundation seed producers. In two years, a total of 45,500 seeds from 91 seed samples from 43 sources (farmers, seed companies and research) were tested for seed-borne bacteria and fungi by plating disinfested seed onto an agar medium. The most commonly isolated plant pathogens were Fusarium oxysporum (69% of the samples), Macrophomina phaseolina (76%) and Pseudomonas syringae pv. phaseolicola (48%). The infection incidence, the percentage of seeds infected per sample, varied from 0.2 to 75.6%. F. oxysporum had a median infection incidence of 9% in 2009 and 25% in 2010, while M. phaseolina had a median infection between 4 and 10%. On average, 8.8 species per sample were isolated from foundation seed, 9.2 from farmer-produced seed and 9.8 from seed companies' seed. No evidence was found that seed recycling in the informal SS did lead to increased levels of seed-borne pathogens. In contrast to farmers, seed companies distribute seed over large distances, and therefore form a potential threat for spreading diseases at relatively large scale. Responsible authorities are recommended to make seed dressing mandatory for all seeds sold by seed companies.
    Are investments in an informal seed system for cowpea a worthwhile endeavour?
    Biemond, P.C. ; Stomph, T.J. ; Kamara, A. ; Abdoulaye, T. ; Hearne, S. ; Struik, P.C. - \ 2012
    International Journal of Plant Production 6 (2012)3. - ISSN 1735-6814 - p. 367 - 385.
    developing-countries
    High seed quality is a critical component for realising yield potential. For smallholder cowpea farmers in northern Nigeria the informal seed system is a major supplier of genetically high-quality seed, but the physiological quality of farmers’ produced seed remains unknown. The project “Promoting Sustainable Agriculture in Borno State” (PROSAB) trained and supported farmers in seed production in Borno State, Nigeria. We analysed the quality of farmers’ produced cowpea seed based on standard quality testing criteria, and evaluated its field emergence as a proxy for non-genetic seed quality. We carried out a survey among seed producing farmers about their production and storage practices, and tested seed quality of samples from these farmers, from seed companies and compared these to foundation seed. Field emergence of farmers’ produced seed was not significantly different from that of foundation seed (P=0.47) or seed company samples (P=0.12). Cowpea seed quality, however, was inadequate in both the formal and informal seed systems. Five out of six foundation seed samples, 79 out of 81 samples of farmers’ seed, and six out of six seed company samples failed to meet standards for foundation and certified seeds of the National Agriculture Seed Council (NASC), the seed industry regulatory agency in Nigeria. Multiple regression analyses predicting field emergence showed that projects like PROSAB can improve seed quality. Especially proper storage and reducing seed damage can increase field emergence significantly. Our findings suggest that it is worth to invest in improving the informal seed system of cowpea
    Naar een geïntegreerde wijze van tripsbestrijding in de Brabantse preiteelt
    Biemond, H. ; Hadders, J. ; Ravensberg, W. ; Boer, R. de; Belder, E. den - \ 2004
    Provincie Noord-Brabant : Productschap Tuinbouw (PT rapport ) - 21 p.
    Role of cobalamin intake and atrophic gastritis in mild cobalamin deficiency in older Dutch subjects.
    Asselt, D.Z.B. van; Groot, C.P.G.M. de; Staveren, W.A. van; Blom, H.J.M. ; Wevers, R.A. ; Biemond, I. ; Hoefnagels, W.H.L. - \ 1998
    American Journal of Clinical Nutrition 68 (1998). - ISSN 0002-9165 - p. 328 - 334.
    Effects of nitrogen on accumulation and partitioning of dry matter and nitrogen of vegetables. 3. Spinach.
    Biemond, H. ; Vos, J. ; Struik, P.C. - \ 1996
    Netherlands Journal of Agricultural Science 44 (1996). - ISSN 0028-2928 - p. 227 - 239.
    Four greenhouse and 2 field experiments (the latter on a sandy soil) were carried out with different amounts and dates of N application to analyse the dynamics of dry matter and N accumulation in spinach (cv. Trias). Frequent measurements were carried out on dry matter and N accumulation in leaf blades, petioles and stems. The total accumulation of dry matter and N differed largely among and within experiments. Increasing N application increased yield of dry matter and N accumulation, whereas splitting N applications had much smaller effects. However, the partitioning of dry matter and N proved insensitive to N treatments. Harvest indices for dry matter (about 0.67) or N (about 0.74) of crops at a marketable stage were fairly constant over treatments and experiments. Increasing or splitting the N application affected N accumulation more than dry matter production, resulting in large effects on N concentrations. The lack of variation in response to N for different N regimes facilitates the development of N application techniques aimed at high yield, high quality and reduced emissions. The organic N concentration of leaf blades and petioles decreased with leaf age, although in most experiments this decrease was smaller at higher leaf numbers. The nitrate-N concentration decreased with increasing leaf number at any sampling date; it was higher when N was abundant. High yields in autumn crops were associated with high nitrate concentrations but also with potentially high losses of N.
    Dynamics of change of leaf attributes of Brussels sprouts in response to switches between high and low supply of nitrogen.
    Vos, J. ; Biemond, H. ; Struik, P.C. - \ 1996
    Netherlands Journal of Agricultural Science 44 (1996). - ISSN 0028-2928 - p. 31 - 42.
    In a greenhouse pot experiment with Brussels sprouts grown in sand, 4 treatments were compared: a control without N limitation, a continuously N-deficient control and 2 treatments with a switch from the high to the low supply or vice versa. All treatments received nutrient solution at 9 dates during the experiment. The high-N and low-N controls received 1.96 and 0.56 g/application, respectively. In the high-low treatment the switch from the higher to the lower application rate took place 57 days after planting (DAP) and in the low high treatment the reverse switch took place 85 DAP; these 2 treatments received the same total amount of N. Plant N concentrations changed rapidly upon changes in N supply regime. When the supply rate was increased, N concentration increased in leaves that had completed their expansion. Changes in leaf growth started about 15 days after the switch in N regime. Leaves that were expanding at the switch responded by increase in area when N supply increased without a change in mass, i.e. specific leaf area increased. Leaf areas and specific leaf area of expanding leaves decreased when the N supply became smaller. The control of leaf size during initiation and expansion is discussed.
    Effects of nitrogen on accumulation and partitioning of dry matter and nitrogen of vegetables. 1. Brussels sprouts.
    Biemond, H. ; Vos, J. ; Struik, P.C. - \ 1995
    Netherlands Journal of Agricultural Science 43 (1995). - ISSN 0028-2928 - p. 419 - 433.
    Three greenhouse trials and one field trial were carried out on Brussels sprout cv. Icarus SG2004 in which the treatments consisted of different N amounts and application dates. DM and N accumulation in stems, apical buds and groups of leaf blades, petioles and sprouts were measured frequently throughout crop growth. Total amounts of accumulated DM and N were affected by amount of N applied and date of application, but the final harvest indexes for DM and N (0.10-0.35 and 0.20-0.55, respectively) were not significantly affected by treatments in most experiments. Nitrate N concentrations were only high (up to about 2%) shortly after planting. The total N concentration of leaf blades and petioles increased with increasing leaf number. This increase resulted from a decreasing N concentration during the leaf's life. The total N concentration in sprouts changed little with leaf number.
    Effects of nitrogen on accumulation and partitioning of dry matter and nitrogen of vegetables. 2. Leek.
    Biemond, H. - \ 1995
    Netherlands Journal of Agricultural Science 43 (1995). - ISSN 0028-2928 - p. 435 - 446.
    Two greenhouse and 2 field trials were carried out on leeks cv. Albana with different N fertilizer rates and application dates. Observations included frequent measurements of DM and N accumulation in leaf blades, leaf sheaths and, if present, scapes. Both the amount of N applied and the time of application affected the total accumulation of DM and N in the plant. The relative partitioning rates of DM increase to the shaft were affected in such a way that the final harvest indices for DM (which ranged from 0.32 to 0.53) were significantly lower at higher N application rates. The final harvest indices for N (0.21-0.35) were not significantly affected by amount or timing of fertilizer applications. The total N concentrations of leaf blades and leaf sheaths decreased with increasing leaf age. Average nitrate N concentrations over all plant parts were always below 40%.
    Effects of nitrogen on development and growth of the leaves of vegetables. 3. Appearance and expansion growth of leaves of spinach.
    Biemond, H. - \ 1995
    Netherlands Journal of Agricultural Science 43 (1995). - ISSN 0028-2928 - p. 247 - 260.
    In a series of greenhouse and field trials, spinach cv. Trias plants were supplied with different amounts of N fertilizer in various split applications. Rates of leaf emergence and expansion were recorded, as well as final leaf size. The rate of leaf appearance varied between 0.16 and 0.57/day across experiments, but was hardly affected by N treatment. The rate of leaf expansion and mature leaf area increased with leaf number, reaching maximum values at leaf pair 3 4 or 5 6 and decreasing subsequently. Both characteristics were positively correlated with N supply. The duration of expansion was not influenced by N treatments and varied between 15 and 30 days in most experiments. The rate of leaf expansion was the main factor determining mature leaf size. Specific leaf area over all green leaves slowly decreased with time in most experiments and was around 300 cmsuperscript 2/g. As the differences in the number of leaves were small, the differences in total green leaf area per plant resulted from differences in the areas of individual mature leaves.
    Effects of nitrogen on development and growth of the leaves of vegetables. 2. Appearance, expansion growth and life span of leaves of leek plants.
    Biemond, H. - \ 1995
    Netherlands Journal of Agricultural Science 43 (1995). - ISSN 0028-2928 - p. 233 - 246.
    In greenhouse pot experiments and field trials, leek cv. Albana plants were supplied with different amounts of N fertilizer at various growth stages. Leaf emergence, expansion, size and senescence were monitored. The rate of leaf appearance was not affected by N treatments and almost constant across experiments at 0.15/day. The rate of leaf expansion and the mature leaf area increased with leaf number, reaching maximum values between leaf numbers 11 and 14 and decreasing with higher leaf numbers. Both variables increased with increasing N application rate. The duration of leaf expansion was more or less constant across leaf numbers and not influenced by N treatments; the leaf expansion rate was the main factor determining mature leaf area. The rate of leaf senescence was not influenced by N treatments. Differences in total green leaf area per plant were caused by differences in the area of individual mature leaves and not by differences in the number of leaves. The specific leaf area of all leaves was more or less constant at 100 cmsuperscript 2/g.
    Nitrogen nutrition effects on development, growth and nitrogen accumulation of vegetables
    Biemond, H. - \ 1995
    Agricultural University. Promotor(en): P.C. Struik; J. Vos. - S.l. : Biemond - ISBN 9789054854289 - 171
    stikstof - allium cepa - uien - spinacia oleracea - spinazie - solanum tuberosum - aardappelen - brassica oleracea var. gemmifera - spruitjes - groei - gewassen - plantenfysiologie - plantenontwikkeling - bladeren - nitrogen - allium cepa - onions - spinacia oleracea - spinach - solanum tuberosum - potatoes - brassica oleracea var. gemmifera - brussels sprouts - growth - crops - plant physiology - plant development - leaves

    In order to be able to match nitrogen supply and nitrogen requirement of vegetable crops, insight is necessary in the responses to nitrogen of important processes of growth and development. This study focused on effects of amount of nitrogen applied and fractionation of nitrogen supply on leaf attributes, accumulation and partitioning of dry matter and nitrogen in potato (Solanum tuberosum L.), Brussels sprouts ( Brassica oleracea L. var gemmifera DC), leek ( Allium porrum L.) and spinach ( Spinacia oleracea L.). Effects of amount of nitrogen applied were always much more important than effects of fractionation of nitrogen supply.

    Rate of leaf appearance varied among crops from 0. 15-0.60 leaves d -1; it increased with more nitrogen in Brussels sprouts and spinach. Rates of leaf senescence were enhanced by nitrogen in Brussels sprouts. Life span of leaves was about 70 d for all crops. Rates of leaf expansion and maximum sizes of leaves increased with leaf number until a certain leaf number after which they gradually decreased. Both characteristics increased with more nitrogen. Duration of leaf expansion varied among crops from 18-40 d and decreased in Brussels sprouts with more nitrogen. Maximum size of a leaf was mainly determined by rate of leaf expansion. Except in potato, more nitrogen increased specific leaf area. Differences among nitrogen treatments in total green leaf area reflected the effects of nitrogen on rates of leaf expansion.

    Total dry matter production was strongly related to leaf area duration. Although more nitrogen applied resulted in more nitrogen taken up and more total dry matter produced, considerable variation was observed in the relation between total nitrogen uptake and total dry matter production. Harvest indices for dry matter varied among crops and treatments from about 0.10-0.87; more nitrogen increased it for Brussels sprouts, but decreased it for leek. Harvest indices for nitrogen varied from about 0.22-0.86; more nitrogen increased it for Brussels sprouts. In general, organic nitrogen concentration increased with increasing node number for leaf blades, petioles and leaf sheaths but not for sprouts. The gradient with node number resulted from a decreasing nitrogen concentration during the leafs life. High nitrate concentrations in the marketable produce were only observed in spinach. Nitrate nitrogen concentrations of leaf blades, petioles and leaf sheaths decreased with increasing leaf number at any time of observation, but were not related to leaf age. However, in stems of Brussels sprouts and stems and tubers of potato, total nitrogen and nitrate nitrogen concentration were closely related.

    The present findings elucidate the reactions of the crops to nitrogen fertilisation. This is helpful for the fine-tuning of nitrogen fertilisation and to develop modules on plant development in crop simulation models.

    Effects of nitrogen on development and growth of the leaves of vegetables. 1. Appearance, expansion growth and life span of leaves of Brussels sprouts plants.
    Biemond, H. ; Vos, J. ; Struik, P.C. - \ 1995
    Netherlands Journal of Agricultural Science 43 (1995). - ISSN 0028-2928 - p. 217 - 232.
    In greenhouse pot experiments and field trials, leek cv. Albana plants were supplied with different amounts of N fertilizer at various growth stages. Leaf emergence, expansion, size and senescence were monitored. The rate of leaf appearance was not affected by N treatments and almost constant across experiments at 0.15/day. The rate of leaf expansion and the mature leaf area increased with leaf number, reaching maximum values between leaf numbers 11 and 14 and decreasing with higher leaf numbers. Both variables increased with increasing N application rate. The duration of leaf expansion was more or less constant across leaf numbers and not influenced by N treatments; the leaf expansion rate was the main factor determining mature leaf area. The rate of leaf senescence was not influenced by N treatments. Differences in total green leaf area per plant were caused by differences in the area of individual mature leaves and not by differences in the number of leaves. The specific leaf area of all leaves was more or less constant at 100 cmsuperscript 2/g.
    Stikstofhuishouding bij de teelt van prei en spruitkool.
    Booij, R. ; Biemond, H. - \ 1994
    In: Themadag Stikstofstromen in de vollegrondsgroenteteelt, Themaboekje nr. 18, A.J. Haverkort et al. (red.). AB-DLO Wageningen/Haren/LU Wageningen/PAGV Lelystad - p. 23 - 36.
    Relations between firm results, firm properties and management abilities of the market gardener on pot plants nurseries in The Netherlands.
    Niejenhuis, J.H. van; Slijkerman, A.J.M. ; Biemond, T. ; Soomer, K. de - \ 1994
    In: Paper 12th Int. Symp. Horticultural Economics. Montpellier - p. 125 - 131.
    Effecten van bemestingsstrategie op gewasstructuur en nitraatgehalte van spruitkool, prei en spinazie.
    Biemond, H. - \ 1994
    In: Themadag Stikstofstromen in de vollegrondsgroenteteelt. Themaboekje nr. 18, A.J. Haverkort et al. (red.). AB-DLO Wageningen/Haren/LU Wageningen/PAGV Lelystad - p. 37 - 51.
    De ontwikkeling, groei en fysiologie van planten in relatie tot abiotische omgevingsfactoren : rapport van een literatuurstudie
    Biemond, H. - \ 1992
    Wageningen : Landbouwuniversiteit (Mededeling / Landbouwuniversiteit, Vakgroep Landbouwplantenteelt en Graslandkunde no. 105) - 47
    plantenfysiologie - plantenontwikkeling - groei - milieufactoren - plant physiology - plant development - growth - environmental factors
    De ontwikkeling, groei en fysiologie van planten in relatie tot abiotische omgevingsfactoren.
    Biemond, H. - \ 1992
    Unknown Publisher (Mededeling vakgroep Landbouwplantenteelt en Graslandkunde 105) - 47 p.
    Effects of nitrogen on the development and growth of the potato plant. 1. Leaf appearance, expansion growth, life span of leaves and stem branching.
    Vos, J. ; Biemond, H. - \ 1992
    Annals of Botany 70 (1992). - ISSN 0305-7364 - p. 27 - 35.
    Effects of nitrogen on the development and growth of the potato plant. 2. The partitioning of dry matter, nitrogen and nitrate.
    Biemond, H. ; Vos, J. - \ 1992
    Annals of Botany 70 (1992). - ISSN 0305-7364 - p. 37 - 45.
    A tomato growth model as part of a bio-economic model.
    Biemond, T. - \ 1989
    Acta Horticulturae 260 (1989). - ISSN 0567-7572 - p. 285 - 293.
    gewassen, groeifasen - groeistadia - solanum lycopersicum - modellen - teelt onder bescherming - onderzoek - tomaten - crop growth stage - growth stages - solanum lycopersicum - models - protected cultivation - research - tomatoes
    A growth model for heated glasshouse tomatoes is described in detail. A mechanistic approach is used so that both development and real growth are distinguished for both crop and fruit. Some results of the growth model as part of a bio-economic model are given. Of the different phsyiological processes, the rate of photosynthesis showed the largest influence on productivity. Other regarded aspects are: rate of flowering and maturing, tomato type, intercropping and planting date.
    A glasshouse climate model as part of a bio-economic model.
    Biemond, T. - \ 1989
    Acta Horticulturae 260 (1989). - ISSN 0567-7572 - p. 275 - 284.
    klimaat - analyse van besluiten - besluitvorming - kassen - modellen - teelt onder bescherming - onderzoek - climate - decision analysis - decision making - greenhouses - models - protected cultivation - research
    Bio-economic models can be used as base for decision support systems. In protected cultivations, the glasshouse climate is of major importance on the financial result, both by costs and by yield. In this paper, a mechanistic climate model is described in detail. This glasshouse climate model is repartioned into four submodels: radiation- and lightintensity, heat- and daily ventilation need, mean day- and 24 hours temperature and a gas consumption submodel. Variation in CO2-concentration and low temperatures, especially at night had a large influence on the productivity.
    Gewasbescherming: zorgzaamheid op lange termijn.
    Biemond, T. - \ 1988
    Maandblad / Suiker Unie 22 (1988)apr. - ISSN 0024-8606 - p. 10 - 11.
    Een zorgvuldige bemesting levert suiker en geld op.
    Biemond, T. - \ 1988
    Maandblad / Suiker Unie 22 (1988)mrt. - ISSN 0024-8606 - p. 8 - 9.
    Invloed van grondbewerking, ras en zaadsoort op het resultaat.
    Biemond, T. - \ 1988
    Maandblad / Suiker Unie 22 (1988)febr. - ISSN 0024-8606 - p. 5 - 6.
    Meedoen aan Unitip bevordert beter resultaat.
    Biemond, T. - \ 1988
    Maandblad / Suiker Unie 22 (1988)jan. - ISSN 0024-8606 - p. 4 - 5.
    A bio-economic model for heated glasshouse tomatoes.
    Biemond, T. ; Trap, W.G. - \ 1988
    In: Proc. ISHS Int. Symp. Models for plant growth environmental control and farm management in protected cultivation, Hannover, FRG (1988) 8 pp
    GROMS, een managementondersteunend systeem voor potplantentuinders.
    Biemond, T. ; Hofstede, G.J. - \ 1988
    In: VIAS-Symp. Informatica-toepassingen in de agrarische sector / Huijbers, C., - p. 115 - 125.
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