Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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.

    We have a manual that explains all the features 

    Current refinement(s):

    Records 1 - 20 / 27

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    Graansorghum-SorghumBicolor / Eiwit en oliepad
    PPO Akkerbouw, Groene Ruimte en Vollegrondsgroente, - \ 2012
    sorghum bicolor - gewassen - graansoorten - voedselgewassen - voedergewassen - brandstofgewassen - vezelgewassen - akkerbouw - biobased economy - sorghum bicolor - crops - cereals - food crops - fodder crops - fuel crops - fibre plants - arable farming - biobased economy
    Factsheet van het Eiwit en Oliepad met korte informatie over het gewas Graansorghum. Met het project Eiwit & Oliepad wil Innovatief Platteland samen met de gemeente Venray en andere partners het publiek de gelegenheid geven zich een beeld te vormen van de enorme multifunctionaliteit en de nog steeds verder te ontdekken mogelijkheden van in Europa te telen gewassen als grondstof voor de biobased economie
    Understanding the diverse roles of soil organic matter in the cereal - Striga hermontica interaction
    Ayongwa, G.C. - \ 2011
    Wageningen University. Promotor(en): Thomas Kuijper, co-promotor(en): Tjeerd-Jan Stomph. - S.l. : s.n. - ISBN 9789085858430 - 131
    striga hermonthica - sorghum bicolor - parasitaire onkruiden - organisch bodemmateriaal - bodemvruchtbaarheid - experimenteel veldonderzoek - stikstof - mineralisatie - beperkingen - gewasproductie - kameroen - nigeria - striga hermonthica - sorghum bicolor - parasitic weeds - soil organic matter - soil fertility - field experimentation - nitrogen - mineralization - constraints - crop production - cameroon - nigeria

    Keywords: Striga hermonthica, Sorghum bicolor, soil fertility, organic matter, N-mineralisation, farmers’ priority, production constraints, intensification.


    The problem of the parasitic weed striga (Striga hermonthica (Del.) Benth.) has worsened for African farmers, in conjunction with degrading soil fertility. An analysis of the striga problem showed that scientists, policy makers and farmers conceptualise striga differently. Whether striga is viewed as a weed or a symptom of degraded soils raises two questions: Should farmers control striga, even when the impact on yields would be negligible? Or should fertility enhancement, leading to higher yields, be their focus, even when not accompanied by an immediate reduction in striga? This study seeks to understand how organic matter inputs affect nutrient dynamics, sorghum (Sorghum bicolor [L.] Moench) production and striga abundance.
    Surveys in northern Cameroon showed that striga infestation increased over the past two decades. Increased land pressure led to reduced fallow periods and enhanced cereal (mono-) cropping. Reduced access to fertiliser and manure hampered options to improve soil fertility. Yields from farmers’ fields did not correlate with striga incidence, confirming farmers’ prioritisation of soil fertility, weeds, and labour as production constraints, rather than striga. The entry point to tackle low yields and the worsening of the striga situation should follow farmers’ priority of alleviating low soil fertility.
    Whether and how soil fertility improvement, through organic matter, enhances agricultural productivity and reduces striga, was investigated in field experiments. Organic matter amendments significantly depressed striga seed survival, with the strongest effect achieved at higher quality; presumably due to higher microbial activity. Organic matter enhanced soil water retention and soil temperature but without effects on striga seed survival. Organic matter did not affect soil ethylene concentrations. The effect of organic matter amendments was directly related to N mineralisation, both for better cereal growth and reduced striga survival. The organic matter amendments and use of fallow, as applied here, however, may not be practicable for the resource-poor farmer.
    Increasing N-fertilisation increased sorghum root N mass concentration, which resulted in a lower striga seed germination. That relationship was linear up to a root N mass concentration of 19.5 mg g-1 where seed germination was close to but always still above 0%.
    In a broader framework of the research findings, the ultimate solution for farm productivity for Africa is in sustainable farm intensification by investing in soil fertility. However, the prevailing land tenure system and limited access to fertiliser and organic matter need to be overcome. A new conceptual model is proposed, indicating how changes in both cereal yield and striga infestation over time co-vary with changes in soil fertility. The implication of this model is that recovery of soil fertility should be the priority. The challenge to agronomists remains to consider how to make farm intensification rewarding and attainable for resource-poor farmers. In areas where striga is an obstacle, an integrated scheme for the intensification of cereal cropping should start with integrated soil fertility management. Crop rotation and intercropping with selected non-host leguminous crops are essential ingredients.

    Integrating science with farmer knowledge: Sorghum diversity management in north-east Ghana
    Kudadjie, C.Y. - \ 2006
    Wageningen University. Promotor(en): Paul Richards; Paul Struik, co-promotor(en): S.K. Offei; P.B. Atengdem. - Wageningen : WUR - ISBN 9789085044406 - 220
    farmers - knowledge - indigenous knowledge - management - sorghum - species diversity - genetic diversity - plant genetic resources - innovations - agricultural research - ghana - sorghum bicolor - boeren - kennis - inheemse kennis - bedrijfsvoering - sorghum - soortendiversiteit - genetische diversiteit - genetische bronnen van plantensoorten - innovaties - landbouwkundig onderzoek - ghana - sorghum bicolor
    Keywords:   Convergence of sciences, diversity management, experimentation, farmer knowledge, genetic diversity, Ghana, plant variation, private sector, research, Sorghum bicolor (L.)Moench, small-scale farmers, seed quality.

    Sub-optimal impact of agricultural research is connected to lack of involvement of farmers. This is especially true forAfricawhere problems are diverse and complex. Farmer participation might help research to become better focused and resulting technologies more adopted. However, linking researchers and farmers effectively in research is not easy. Even though African farmers are often very innovative, technology development is influenced by other stakeholders and takes place within a wide institutional context and policy framework over which farmers have little control. Convergence of Sciences offers an alternative way of organizing research whereby the agricultural innovation process is recognized as a multi-stakeholder process.

    This thesis situates science and farmer initiative within the context of sorghum genetic resource management. Sorghum plays a pivotal role in the agrarian life and culture of small farmers in north-eastGhana. The value of genetic diversity for farmers provides strong justification for placing emphasis on, and pursuing research into, two main areas: the need to support farmers' own efforts in diversity management and variety maintenance, and - as an important component of that aspect - the need to pay attention to farmers' seed management and storage practices.

    The thesis shows how farmers and scientists can effectively engage in agricultural research towards a sustainable use and management of sorghum genetic resources. Convergence is explored between researchers and farmers and between the biosciences and social sciences. The possibility for convergence between farmers, public sector researchers and private sector interests under market-driven conditions for sorghum production is also explored.

    The results indicate that joint learning and experimentation under local conditions is a useful and effective means through which unschooled small-scale farmers and scientists can actively engage in the research process. Such an approach provides the opportunity for an intensive and sustained interaction between both farmers and scientists. Going along the pathway of experimentation has shown that farmers are capable of joining in scientific research, have an indigenous capacity for astute observation, and are capable of forming a good working notion of science as it is practised in the formal sector. However, a conscious effort must be made to embed these scientific principles in the farmers' local and cultural context in order to make the capability of farmers as co-researchers become more apparent. Through farmers' own analysis (facilitated and stimulated by researchers) of test data, they correctly infer that in order to improve the physiological seed quality of their early maturing varieties, they need to pay closer attention to the conditions under which harvesting, seed selection, and storage occur.

    Scientific methods and tools from the biological and social science disciplines are used for gathering and analysing qualitative and quantitative data during the joint learning and experimentation phase of the study and for generating knowledge. Molecular marker techniques from bioscience helped to determine the extent of diversity used by farmers, while anthropological information provided a deeper understanding of how cultural and socio-economic factors influence farmers' use and management of sorghum varieties.

    The case of contract farming provided the important lesson that making contract farming work is often contingent upon mobilizing both technical and farmer knowledge for technological problem solving. Making technology part of the contracting process helps reinforce among all contracting parties the need to work jointly towards effective solutions to production problems in an uncertain world where effective new knowledge is at a premium. This requires the recognition by contracting companies of the fact that where the technology is an important problem, offering ways of negotiating about the various contributions of relevant parties in the contract would lead to better application of technology.

    Sorghum remains an important crop for farmers who stand to gain a lot more if researchers commit and apply themselves to partnership with farmers as co-researchers. This thesis has thrown some light on how such partnerships for new and effective knowledge might evolve. Convergence of Sciences, as an alternative approach to the linear model of planning, designing and implementing research, appears to hold much promise for small farmers such as those found in the north-eastern part ofGhana
    Effects of soil amendments and drought on zinc husbandry and grain quality in Sahelian sorghum
    Traore, K. - \ 2006
    Wageningen : Wageningen University and Research Centre (Tropical resource management papers no. 74) - ISBN 9789085850670 - 162
    sorghum - sorghum bicolor - grondverbeteraars - droogte - graan - kwaliteit - zinkmeststoffen - landbouwplantenteelt - sorghum - sorghum bicolor - soil amendments - drought - grain - quality - zinc fertilizers - crop husbandry
    Effects of soil amendments and drought on zinc husbandry and grain quality in Sahelian sorghum
    Traore, K. - \ 2006
    Wageningen University. Promotor(en): Leo Stroosnijder; Paul Struik, co-promotor(en): Tjeerd-Jan Stomph. - [S.l.] : S.n. - ISBN 9789085044376 - 162
    sorghum - sorghum bicolor - grondverbeteraars - droogte - graan - kwaliteit - zinkmeststoffen - landbouwplantenteelt - sorghum - sorghum bicolor - soil amendments - drought - grain - quality - zinc fertilizers - crop husbandry
    In developing countries, short supply of Zinc is limiting both crop yield and human health. Improving Zn bio-availability in staple foods would greatly improve public health. It¿s therefore a major challenge to design cereal production techniques resulting in higher Zn mass fractions (MF) in combination with a lower phytic acid (IP-6, the main form of phosphorus accumulation in the grain) MF. In northern Burkina Faso, soil and water conservation (SWC) and soil organic amendments (SOAs) techniques adopted by farmers have improved both water and nutrient availability which consequently increased crop yields. Potentially, this improvement in yield may also improve the bio-availability of Zn from staple foods. This research investigated possible modifications of SOAs as currently practiced by farmers, which increase both the quality and the yield of sorghum in the Sahel
    The influence of time and severity of Striga infection on the Sorghum bicolor - Striga hermonthica association
    Ast, A. van - \ 2006
    Wageningen University. Promotor(en): Martin Kropff, co-promotor(en): Lammert Bastiaans. - Wageningen : s.n. - ISBN 9789085043997 - 154
    striga hermonthica - striga - parasitaire planten - onkruiden - sorghum bicolor - sorghum - infectie - aantasting - onkruidbestrijding - plantenecologie - ecofysiologie - striga hermonthica - striga - parasitic plants - weeds - sorghum bicolor - sorghum - infection - infestation - weed control - plant ecology - ecophysiology
    Keywords: Striga hermonthica , Sorghum bicolor , infection time, infection level, tolerance.

    This thesis presents the results of a study on the interaction between the parasitic weed Strigahermonthica (Del.) Benth. and sorghum ( Sorghum bicolor [L.] Moench). The main objective of the study was to investigate the effects of time and level of Striga infection on the interaction between host plant and parasite. Consequences for sorghum performance and the growth and development of the parasite were examined. A comparison between two sorghum cultivars differing in level of Striga tolerance, revealed that the absence of a negative effect of Striga infection on photosynthetic rate and a delayed time of first Striga infection both contributed to the lower extent of yield reduction of the tolerant cultivar. Likewise, in an experiment with a wide range of Striga seed infestation levels, it was observed that higher soil infestations levels did not only result in a higher Striga infection level, but also in an advanced time of first Striga infection.The importance of time of infection was further investigated in a pot experiment in which the time of infection was artificially delayed.Striga parasitism and reproduction, and the detrimental effects of Striga on crop performance could be strongly reduced by delaying the time of first infection. Prospects of reducing Striga parasitism by means of cultural control methods that are based on the principle of a delayed onset of Striga attachment were assessed. In a pot experiment, the combination ofshallow soil tillage, deep planting and the use of transplantsresulted in a four-week delay in first emergence of the parasite, a strongly reduced infection level of the sorghum host and highly improved sorghum yields. Evaluation of these methods under field conditions resulted in a 85% reduction in Striga -infection level, but as no delay in time of parasite infection was established, no beneficial effect on crop yield was obtained. Potential causes of the absence of a delay in Striga infection time under field conditions were discussed and alternative options for establishing a delayed infection in the field were proposed.
    The influence of time and severity of Striga infection on the Sorghum bicolor - Striga hermonthica association
    Ast, A. van - \ 2006
    Wageningen : Wageningen University and Research Centre (Tropical resource management papers no. 77) - ISBN 9789085850588 - 154
    striga hermonthica - striga - parasitaire planten - onkruiden - sorghum bicolor - sorghum - infectie - aantasting - onkruidbestrijding - plantenecologie - ecofysiologie - striga hermonthica - striga - parasitic plants - weeds - sorghum bicolor - sorghum - infection - infestation - weed control - plant ecology - ecophysiology
    Getting genes: Rethinking seed system analysis and reform for sorghum in Ethiopia
    McGuire, S. - \ 2005
    Wageningen University. Promotor(en): Paul Richards, co-promotor(en): Conny Almekinders. - Wageningen : - ISBN 9789085041795 - 279
    plantenveredeling - sorghum - sorghum bicolor - zaden - zaadkwaliteit - boeren - bedrijfssystemenonderzoek - genetische bronnen van plantensoorten - ethiopië - inheemse kennis - opslag van zaden - plant breeding - sorghum - sorghum bicolor - seeds - seed quality - farmers - farming systems research - indigenous knowledge - plant genetic resources - ethiopia - seed storage
    Crop improvement and seed supply are central activities in agricultural development. Many interventions have sought to involve farmers more closely in crop development and seed supply, to improve the effectiveness of plant science, enhance biodiversity conservation, or empower farmers, with Participatory Plant Breeding' (PPB) being the most recent strategy for reform. However, there is little critical analysis of the existing technical and institutional practices of formal systems, and almost no knowledge at all of farmers' own strategies for accessing and using crop genetic resources. For these reasons, interventions risk being mis-directed. Moreover, without a broad analysis of institutions and policies, interventions may result lead to only temporary change, at best. This research analyses both farmer and formal seed systems for sorghum inEthiopia, identifying the specific challenges they face, set in historical, social, and institutional context. This is rarely done in discussions of reform, and suggests different that different types of interventions are needed than usually promoted by PPB, or other participatory reforms. Using practice and path-dependency as analytical starting points, this thesis explores the history, policies, key decisions, and institutional cultures in formal breeding and seed supply. Farmers own genetic resource management was directly observed in two communities, using both qualitative and quantitative approaches to explore social relations in seed exchange, seed storage and selection, and pathways of innovation. This broad scaled-approach highlighted how biological and social process interact in genetic resource management, particularly around the institutional forces shaping formal seed system practices, and the importance of social relationships in securing access to seed and germplasm in farmer seed systems. Analysing both seed systems together in this inter-disciplinary fashion offers fresh insights into seed system reform, and highlights key challenges, particularly in relation to securing access to seed and information, appropriate scale of work, and institutional barriers to change.
    The role of sorghum genotype in the interaction with the parasitic weed Striga hermonthica
    Rodenburg, J. - \ 2005
    Wageningen University. Promotor(en): Martin Kropff, co-promotor(en): Lammert Bastiaans. - Wageningen : - ISBN 9789085042761 - 138
    sorghum bicolor - sorghum - striga hermonthica - parasitaire planten - genotype-milieu interactie - genetische parameters - selectiemethoden - genetisch bepaalde resistentie - plantenveredeling - gevoeligheid van variëteiten - sorghum bicolor - sorghum - striga hermonthica - parasitic plants - genotype environment interaction - genetic parameters - selection methods - genetic resistance - plant breeding - varietal susceptibility
    Keywords:Strigahermonthica , Sorghum bicolor , selection measures, resistance, tolerance, genotypes.

    This thesis presents a study on the interaction between the parasitic weed Striga(S.hermonthica [Del.] Benth.) and the cereal crop sorghum ( S. bicolor [L.]Moench).Its main objective was to find suitable measures for the selection of breeding material (crop genotypes) with superior levels of resistance or superior levels of tolerance to Striga.To meet this objective the physiological background of tolerance, the relation between Striga infestation, infection and yield loss and the effect of host genotype on Striga parasitism and reproductionwere studied.

    These host-parasite interactions were studied with 4-10 different sorghum genotypes differing in level and mechanism of defence against Striga . Field experiments carried out inMaliwere used for yield assessments and development and validation of selection measures. Through pot and agar-gel experiments, aboveground resistance measures were validated with observations on belowground stages. Pot experimentation was also used to create infection response curves and to measure photosynthesis and chlorophyll fluorescence to develop tolerance measures.

    Strigaparasitism and reproduction, and the detrimental effect of Striga on crop yield can significantly be reduced through crop genotype choice. Maximum aboveground Striga number is a reliable selection measure for resistance. Striga flowerstalk dry weight can be used to identify genotypes that reduce Striga reproduction. The maximum relative yield loss is a suitable selection measure for tolerance in susceptible genotypes, while for more resistant genotypes the relative yield loss per Striga infection seems more appropriate. For these tolerance measures, yield assessment of nearby uninfected controls is indispensable. Chlorophyll fluorescence, more precisely photochemical quenching and electron transport rate, may enable screening for tolerance without this requirement.
    Input levels and intercropping productivity: exploration by simulation
    Wubs, A.M. ; Bastiaans, L. ; Bindraban, P.S. - \ 2005
    Wageningen : Plant Research International (Nota note 369) - 100
    sorghum bicolor - sorghum - vigna unguiculata - vignabonen - teeltsystemen - tussenteelt - simulatiemodellen - input van landbouwbedrijf - watergebruiksrendement - afrika - sorghum bicolor - sorghum - vigna unguiculata - cowpeas - cropping systems - intercropping - simulation models - farm inputs - water use efficiency - africa
    Voorstudie van het effect van verschillende niveaus van waterinput op een sorghum-cowpea intercrop
    De drieweg interactie tussen sorghum, Striga hermonthica en arbusculaire mycorrhiza schimmels
    Lendzemo, V.W. - \ 2004
    Gewasbescherming 35 (2004)6. - ISSN 0166-6495 - p. 319 - 322.
    striga hermonthica - striga - mycorrhizae - sorghum bicolor - sorghum - planteninteractie - onkruidbiologie - kameroen - striga hermonthica - striga - mycorrhizas - sorghum bicolor - sorghum - plant interaction - weed biology - cameroon
    Striga hermonthica is a major biological constraint to cereal production in Africa. The intricate association between this phytoparasite and the cereal host makes management difficult. Damage to the host begins before Striga comes out of the soil. Also, infestation correlates negatively with soil fertility. Arbuscular mycorrrhizal (AM) fungi have a variety of ecological functions ranging from improved uptake of immobile nutrients, protection of host from pathogens, to soil aggregation. The question whether these beneficial micro-organisms could play a role within the Striga-cereal (patho)system was addressed. Inoculating Striga-infested sorghum with AM fungi in pots or in the field resulted in a significant reduction in the performance of Striga in terms of numbers attached to the roots, relative time of emergence, numbers emerged and dry weight of Striga shoots at sorghum harvest. AM effects on Striga were more pronounced with the Striga-tolerant S-35 sorghum cultivar compared to effects with the Striga-sensitive CK60B. Inoculation with AM fungi compensated for damage by Striga in the S-35 cultivar. This compensation was independent of AM inoculum density and was not affected by P application. Germination of preconditioned Striga seeds after exposure to root exudates from sorghum colonized by AM fungi was significantly reduced, with effects more prominent with exudates from S-35 plants. AM fungi have the potential to affect Striga during germination, attachment, emergence, and possibly subsequent growth and development. It is important to understand the kind of management practices that farmers can apply to enhance mycorrhizal performance in an integrated management system
    The tripartite interaction between sorghum, Striga hermonthica, and arbuscular mycorrhizal fungi
    Lendzemo, V.W. - \ 2004
    Wageningen : Wageningen University and Research Centre (Tropical resource management papers 55) - ISBN 9789067547543 - 112
    striga hermonthica - striga - mycorrhizae - sorghum bicolor - sorghum - planteninteractie - onkruidbiologie - kameroen - striga hermonthica - striga - mycorrhizas - sorghum bicolor - sorghum - plant interaction - weed biology - cameroon
    The tripartite interaction between sorghum, Striga hermonthica, and arbuscular mycorrhizal fungi
    Lendzemo, V.W. - \ 2004
    Wageningen University. Promotor(en): Martin Kropff, co-promotor(en): Thomas Kuijper. - [S.l.] : S.n. - ISBN 9789085040309 - 112
    striga hermonthica - striga - mycorrhizae - sorghum bicolor - sorghum - planteninteractie - onkruidbiologie - kameroen - striga hermonthica - striga - mycorrhizas - sorghum bicolor - sorghum - plant interaction - weed biology - cameroon
    Striga hermonthica is a major biological constraint to cereal production inAfrica. The intricate association between this phytoparasite and the cereal host makes management difficult. Damage to the host begins before Striga comes out of the soil. Also, infestation correlates negatively with soil fertility. Arbuscular mycorrrhizal (AM) fungi have a variety of ecological functions ranging from improved uptake of immobile nutrients, protection of host from pathogens, to soil aggregation. The question whether these beneficial micro-organisms could play a role within the Striga -cereal (patho)systemwas addressed. Inoculating Striga -infested sorghum with AM fungi in pots or in the field resulted in a significant reduction in the performance of Striga in terms of numbers attached to the roots, relative time of emergence, numbers emerged and dry weight of Striga shoots at sorghum harvest. AM effects on Striga were more pronounced with the Striga -tolerant S-35 sorghum cultivar compared to effects with the Striga -sensitive CK60B. Inoculation with AM fungi compensated for damage by Striga in the S-35 cultivar. This compensation was independent of AM inoculum density and was not affected by P application. Germination of preconditioned Striga seeds after exposure to root exudates from sorghum colonized by AM fungi was significantly reduced, with effects more prominent with exudates from S-35 plants. AM fungi have the potential to affect Striga during germination, attachment, emergence, and possibly subsequent growth and development. It is important to understand the kind of management practices that farmers can apply to enhance mycorrhizal performance in an integrated management system.
    A model study on population dynamics of Striga that can infect a newly developed resistant Sorghum crop, with practical guidelines to safeguard the sustainability of resistant Sorghum varieties
    Kempenaar, C. ; Davies, J.A.R. ; Scheepens, P.C. - \ 2003
    Wageningen : Plant Research International (Note / Plant Research International 259) - 21
    striga hermonthica - striga - parasitaire planten - onkruiden - populatiedynamica - genetisch bepaalde resistentie - sorghum bicolor - zaadbanken - teeltsystemen - simulatiemodellen - tropen - striga hermonthica - striga - parasitic plants - weeds - population dynamics - genetic resistance - sorghum bicolor - seed banks - cropping systems - simulation models - tropics
    Glucuronoarabinoxylans from sorghum grain
    Verbruggen, M.A. - \ 1996
    Agricultural University. Promotor(en): A.G.J. Voragen; G. Beldman. - S.l. : Verbruggen - ISBN 9789054855026 - 131
    sorghum bicolor - polysacchariden - structuur - chemische reacties - sorghum - sorghum bicolor - polysaccharides - structure - chemical reactions - sorghum

    Water-unextractable cell wall materials (WUS) were prepared from raw, polished, and malted sorghum ( Sorghum vulgare cv. Fara Fara). Except for the amounts, hardly any difference could be observed between the WUS of these three raw materials. This means that cell wall materials of the endosperm cell walls are basically the same as those of the outer endosperm and pericarp layers, and that the cell walls largely persist, during malting. These preparations were further fractionated by a sequential extraction procedure using aqueous solutions of saturated Ba(OH) 2 , 1M KOH and 4M KOH. The WUS preparations were composed of glucuronoarabinoxylans (GAX), (1→3),(1→4)-β-D-glucans, cellulose, and some protein. GAX was primarily extracted by Ba(OH) 2 solutions. All GAX fractions were composed of a highly substituted (1→4)-β-D-xylan backbone, substituted by arabinose and uronic acid. It was concluded that sorghum GAX populations were characterized by a reasonable homogeneity, since they could not be separated further by several chromatographic and precipitation techniques.

    Degradation studies using purified xylanases, arabinofuranosidases and a glucuronidase alone or in combination, showed that the GAX populations were hardly broken down. Some oligomers were formed by digesting Ba(OH) 2 extracted GAX with a combination of endoxylanase I and (1→4)-β-D-arabinoxylan arabinofuranohydrolase, both purified from Aspergillus awamori . These oligomers were found to have a main chain of three or four xylose units, and to contain α-glucuronic acid linked to O -2 of the non-reducing terminal xylose unit. Two oligomers were found to have a dimeric (1→2)-linked arabinose side, chain linked at O -3 of an internal xylose unit. Also single arabinose substitution occured at O -3 of an internal xylose unit. There are strong indications that these side groups can also be linked at O -2 of an internal xylose residue. The reducing xylose units were unsubstituted. A model for the GAX populations from sorghum was proposed combining the results of the degradation studies, the identification of the oligomers, and knowledge about the mode of action of the enzymes used.

    Finally, the developed techniques to investigate GAX in particular, were used to study the behaviour of GAX in the brewing process. Worts and spent grains of mashes, supplemented with commercial enzyme preparations containing xylanases among others were studied. Except for the amount of solubilized GAX, the GAX hardly changed with respect to the sugar composition and molecular weight distribution. A direct relationship between GAX, xylanases, and filtration behaviour of worts prepared from malted sorghum, could therefore not be established.

    Simulation des cultures pluviales au Burkina Faso (CP-BKF3) : sorgho, mil et mais
    Verberne, E. ; Dijksterhuis, G. ; Jongschaap, R. - \ 1995
    Haren (Gr.) : AB-DLO (Nota / AB-DLO 18) - 71
    burkina faso - computersimulatie - maïs - gierst - modellen - onderzoek - simulatie - simulatiemodellen - sorghum bicolor - zea mays - burkina faso - computer simulation - maize - millets - models - research - simulation - simulation models - sorghum bicolor - zea mays
    Manuel du logiciel interactif (CP-BKF3): sorgho, mil et mais
    Bazi, H. ; Sanou, A. ; Verberne, E. - \ 1995
    Haren (Gr.) : AB-DLO (Nota / AB-DLO 20) - 29
    burkina faso - computersimulatie - maïs - gierst - modellen - onderzoek - simulatie - simulatiemodellen - sorghum bicolor - zea mays - burkina faso - computer simulation - maize - millets - models - research - simulation - simulation models - sorghum bicolor - zea mays
    From frustration to information. Diversity in agroecosystems
    Steenhuijsen Piters, B. de - \ 1995
    LEISA : ILEIA newsletter for low-external-input and sustainable agriculture 11 (1995)2. - ISSN 1569-8424 - p. 6 - 7.
    oogsttoename - oogstverliezen - opbrengsten - agrarische bedrijfsvoering - productiviteit - ecologie - gewassen - landbouw - fenologie - acclimatisatie - sorghum bicolor - samenleving - gemeenschappen - onderzoek - kameroen - agro-ecosystemen - yield increases - yield losses - yields - farm management - productivity - ecology - crops - agriculture - phenology - acclimatization - sorghum bicolor - society - communities - research - cameroon - agroecosystems
    Sources of yield variations within one agroecosystem in a village in northern Gabon were investigated combining biophysical, crop genotype and management characteristics of the fields with ethnic and socio-economic characteristics of the households and the farmers. The study shows that diversity and variation should be regarded as important sources of information instead of eliminating them from research
    Diversity of fields and farmers : explaining yield variations in northern Cameroon
    Steenhuijsen Piters, B. de - \ 1995
    Agricultural University. Promotor(en): L.O. Fresco. - S.l. : De Steenhuijsen Piters - ISBN 9789054853442 - 227
    ecologie - gewassen - landbouw - fenologie - acclimatisatie - sorghum bicolor - katoen - oogsttoename - oogstverliezen - opbrengsten - agrarische bedrijfsvoering - kameroen - ecology - crops - agriculture - phenology - acclimatization - sorghum bicolor - cotton - yield increases - yield losses - yields - farm management - cameroon

    This research was inspired by the inability of agricultural research to deal adequately with phenomena of variation, diversity and heterogeneity in agriculture. Although these phenomena were observed as long ago as the beginning of this century, they are still causing concern. Until recently, analysis of variance was applied to any form of undesired variation in the experimental results. The statistical elimination of variation from the research coincided with attempts to uniformise agriculture in order to optimise production. For a long time, deviations from the standardised average were regarded as undesirable random effects.

    Recent research has shown that variations in yield are very common in agroecosystems. They may be large, especially under difficult climatic conditions, and may even be considered as an asset to farmers. There is evidence that variations are not random, but are the result of systematic interaction between environment, crop genotype and management. This agrodiversity has important relations with the higher-level heterogeneity of the environment and diversity of farm households. At present, no comprehensive approach to its analysis is available, largely because agrodiversity is basically multidimensional in nature and may comprise several levels of aggregation.

    The objective of this study was to contribute to the understanding of diversity in agroecosystems by focusing explicitly on variations of yield and their explanation at field and household level. Between 1991 and 1993, field work was done in one village in northern Cameroon. Yield variations of three crops, field properties, crop and management characteristics and household characteristics were assessed systematically. Various techniques for statistical analysis were employed to determine the magnitude of variation and to define the agrodiversity of Within the agroecosystern of the selected village, variations in yield were observed for rainfed sorghum, cotton and dry season sorghum. The magnitude of variation was more or less constant over the years of observation, but varied between the crops. Two rainfed sorghum cropping systems were distinguished and within one cropping system, three field types were defined according to their distance from the homestead. Thus stratified it was possible to reduce overall yield variation and to explain it within each stratum by a reduced number of variables. It was concluded that the composition of agrodiversity was not uniform over the strata. Yield levels, limitations and constraints of rainfed sorghum production were specific to each cropping system and field type.

    Of the three crops, yield variation was greatest in cotton, despite many efforts of the cotton agency to standardise its cultivation. This variation was explained by distinguishing between types of variables, each explaining cotton yield variation to a different degree and in a particular way. Dry season sorghum showed least variation in yield, although it is subject to great environmental stress. Crop genotype and management proved to be adapted to one dominant field property, i.e. the water holding capacity of the soil. All farmers, irrespective of ethnic or socio-economic origin, agreed about the need to adjust mouskouari sorghum cultivation to field characteristics that define the water availability. Processes at field level leading to agrodiversity could be summarised by (1) spatial differentiation of the fields, (2) mechanisation of labour and (3) adaptation of cultivation to the environment.

    Ethnic diversity explained the absolute difference in cotton production, and the distinction between rainfed sorghum cropping systems within the agroecosystem. Socio-economic diversity explained the relative differences in cotton yield, and the distinction between rainfed sorghum field types.

    Finally, gender differences highlighted variations in rainfed sorghum yields and in non-agricultural income. Gender differences and ethnic and socioeconomic diversity proved to be interrelated, resulting in at least three classes of women farmers.

    It must be concluded that within one agroecosystem, crop yields may vary considerably. The agrodiversity explaining these variations proves to be cropspecific, One agroecosystern may comprise several cropping systems and field types of the same crop. Agrodiversity is also spatially specific and is largely determined by ethnic and socio-economic diversity and gender differences at household level. The potentials and problems of crops and fields also prove to be specific to the farmer. Within the context of rural development, it is essential to distinguish between well defined target groups in order to prevent interventions from uneffective generalisation. To do so, variation, heterogeneity and diversity must be accepted as realistic phenomena in agroecosystems and considered as an important source of information.

    Sorghum agronomy in West Kenya : investigations from a farming systems perspective
    Enserink, H.J. - \ 1995
    Agricultural University. Promotor(en): M. Flach. - S.l. : S.n. - ISBN 9789068321005 - 291
    sorghum bicolor - zea mays - maïs - bedrijfssystemen - cultuurmethoden - onderzoek - kenya - sorghum bicolor - zea mays - maize - farming systems - cultural methods - research - kenya

    An adaptive sorghum research and extension programme (1979-82) in West Kenya is reviewed. The focus is on factors operating at farm level. Research results are based on 70 on-farm trials and on some long-term experiments on NPK fertilizer and pest incidence. Extension results are based on two programmes using different approaches. 200 farmers participated in the demonstration approach; in the village approach 100 farmers participated the first year, and 400 the second year.

    The impact of the rainfall pattern on local cropping systems is highlighted with respect to 'first rains' (March-June) and 'second rains' (August-November). Until recently, the short unreliable season of second rains played a minor role. However, current constraints on ox-ploughing result in delays in land preparation. This reduces the growing period for cereal crops during the first rains and increases the risk of failure for local late-maturing varieties. Cropping areas are increasingly restricted to what can be cultivated manually; more farmers are tempted to grow cereal crops during the second rains. As an assured food supply dominates farmer decisions, it was hypothesized that introduction of early- maturing sorghum varieties with a potential for ratooning would increase farmers management flexibility.

    Initial knowledge of effects of sorghum pests, leaf blight and Striga hermonthica proved insufficient. Crop moisture availability analyses commonly used in Kenya do not permit sufficient quantification of variability to understand farmer response to uncertainty. Three types of sorghum cropping seasons must be distinguished based on the variable start of the first rains. These types differ not only in length of growing period but also in shoot fly and midge incidence. Success of late planted crops varies with type of season. Farmers must play each season by ear; conditional recommendations on variety use and time of planting were developed accordingly. Some early-maturing cultivars were selected. However, their ratooning potential proved limited. Hence, attention shifted to planting these cultivars at the start of the second rains. As such plantings are seriously affected by shoot fly, more research on control by seed treatments and cultural methods is required.

    Crop yields and weed composition in farmer fields are related to land use pattern and soil fertility depletion. P is the most limiting nutrient. As N applications often results in negative effects, P/N ratios may play a role. Current socio-economic conditions restrict P applications to first-rain crops to 20 kg/ha P 2 O 5 . Higher levels may only be recommended if residual effects of P on second-rain crops are optimized through land preparation. Row planting with 3 plants/hill is advised as it facilitates placement of P and rapid handhoe weedings.

    The on-farm demonstration approach proved ineffective in stimulating farmer participation in the sorghum technology development process; it puts too much emphasis on selling preconceived messages. Also, the small isolated plots are threatened by birds. In contrast, the village approach proved effective. Its large, clustered plots generated much discussions among farmers and minimized the bird damage threat. Farmer opinions and crop-cut sampling results were used to fine-tune the recommendations for husbandry practices.

    The former compartmentalized research structure in Kenya was not conducive to adaptive research. Insufficient critical mass was available within the small commodity sections at regional level. However, recent interdisciplinary adaptive Regional Research Programmes allow better priority setting. The Farming Systems Approach to Research, Extension and Training is used, which could lead to more demand-driven research.

    Check title to add to marked list
    << previous | next >>

    Show 20 50 100 records per page

     
    Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.