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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Agronomic and socioeconomic sustainability of farming systems : A case in Chencha, South Ethiopia
Dersseh, Waga Mazengia - \ 2017
Wageningen University. Promotor(en): P.C.. Struik, co-promotor(en): R.P.O. Schulte; D. Griffin. - Wageningen : Wageningen University - ISBN 9789463436830 - 157
potatoes - solanum tuberosum - ethiopia - food security - farming systems - mixed farming - sustainability - optimization - efficiency - farm surveys - household surveys - socioeconomics - self sufficiency - profits - training - agronomic characteristics - productivity - soil fertility - rotation - animal feeding - improved varieties - inorganic fertilizers - aardappelen - solanum tuberosum - ethiopië - voedselzekerheid - bedrijfssystemen - gemengde landbouw - duurzaamheid (sustainability) - optimalisatie - efficiëntie - bedrijfsonderzoeken - huishoudonderzoeken - sociale economie - zelfvoorziening - winsten - opleiding - agronomische kenmerken - productiviteit - bodemvruchtbaarheid - rotatie - diervoedering - veredelde rassen - anorganische meststoffen

Potato has multiple benefits and thus can play a vital role in ensuring food security in Ethiopia. However, for diverse reasons, its productivity is low. The farming systems in Ethiopia in which potato is grown, are predominantly mixed farming systems.

Most of the research in Ethiopia is focused on crop-specific constraints and thus there is limited research in which the interrelations between crop and livestock management practices are investigated. There is also not enough research focused on combined analysis of soil nutrient and animal feed balances and agronomic and socioeconomic efficiencies at farm level.

This study assessed production constraints and agronomic and socioeconomic sustainability of the farming systems in South Ethiopia and explored the possible synergetic options to alleviate major constraints. More specifically, the study intended to quantify the variation in input and output among farms, to identify constraints hindering expansion of potato production, to evaluate the sustainability of the farming systems at farm level, to identify constraints of sustainable intensification, and to explore synergetic solutions for the major constraints. Different research approaches were used ranging from lab analysis, household surveys, group discussions, to farm surveys.

Results showed that constraints related to input and product use in potato production vary across households indicating a need for a pluriform advisory model recognizing (and building upon alleviation of) the diversity of constraints identified in this analysis. The sustainability of the farming system is constrained by low agricultural productivity, low soil fertility, poor labour efficiency and limited economic return associated with improper crop rotation, inappropriate soil fertility management practices, shortage of animal feed, labour- and economically inefficient farm practices and labour shortage. However, there is ample scope to overcome the major constraints and simultaneously to optimize farm management.

The core messages of the study can be summarized as follows:

1) the current potato production is characterized by low productivity and economic returns due to various socioeconomic, agronomic and biological factors;

2) the soil fertility is low and there is uneven distribution of nutrients over plots with relatively high fertility levels in the homestead areas;

3) the current labour shortage can be attributed to mainly inefficiency of agricultural management practices and labour migration to towns for economic reasons indicating that the farming system is not sustainable in terms of labour;

4) considering the direct return from animal production, most of the farms had very low gross margin with the current management system and this reduced the overall operating profit of farms. The low return from animal rearing was offset by the relatively high profit from crop production indicating the benefit of mixed farming system in sustaining agricultural production; and

5) each farm can have a wide range of optimized solutions mainly through introduction of improved technologies and subsequent redesigning of the farm managements.

In general, the findings of the current study indicate that it is worthwhile to assess the sustainability of agricultural production in different farming systems and agro-ecologies of Ethiopia. In addition, the combined effect of introducing improved agricultural technologies and subsequent reconfiguring the farm management is very crucial to increase and sustain agricultural production.

Optimization of productivity and quality of irrigated tomato (Solanum lycopersicum L.) by smallholder farmers in the Central Rift Valley area of Oromia, Ethiopia
Gemechis, Ambecha O. - \ 2017
Wageningen University. Promotor(en): P.C. Struik, co-promotor(en): B. Emana. - Wageningen : Wageningen University - ISBN 9789463431576 - 262
solanum lycopersicum - irrigation - crop production - optimization - photosynthesis - chlorophyll - gas exchange - water use efficiency - crop yield - ethiopia - solanum lycopersicum - irrigatie - gewasproductie - optimalisatie - fotosynthese - chlorofyl - gasuitwisseling - watergebruiksrendement - gewasopbrengst - ethiopië

Tomato (Solanum lycopersicum L.) is a vegetable crop with high potential to contribute to poverty reduction via increased income and food security. It is widely grown by smallholders, has high productivity and its demand is increasing. Ethiopia produced about 30,700 Mg of tomatoes on 5,027 ha annually in 2014/2015. Average yields are only 6.1 Mg ha-1, below the world average yields. There is both a need and a potential to increase tomato production per unit area.

The aim of this thesis is to analyze the irrigated tomato production systems of smallholder farmers in Ethiopia, to survey and characterize the tomato in selected ecoregions and seasons, and to identify yield-limiting or yield-reducing factors and opportunities to enhance yield by using a combination of surveys and field experiments. Field experiments on optimization of yield and quality of field-grown tomato were carried out at Ziway, Ethiopia, for two seasons to study the impact of different irrigation practices applied, based on local empirical practices, deficit irrigation, or crop water requirement.

This thesis begins with a survey of tomato production systems. The survey details the area and production in various zones and for each of these zones yield- determining, yield-limiting, and yield-reducing factors and opportunities for improving yield and quality are indicated. It also avails area, production and yield data for each growing season and typifies the production systems in these zones. Low temperature (cold) from October-January and shortage of improved seeds are recognized as yield-determining factors, whereas insufficient water and nutrient (fertilizer) supply proved to be yield-limiting factors across zones. Late blight (Phytophthora infestans), Fusarium wilt (Fusarium oxysporum) and different pests and weeds are identified as yield-reducing factors in the zones. Experienced growers who have access to extension service recorded significant yield increment. Farmers Research Groups improved actual average yield with the use of improved technology (improved varieties and quality seed), and better efficiencies of water and fertilizer use. This study quantified influences of irrigation systems and strategies on growth-determining tomato features. Variation in irrigation systems and strategies accounted for variation in growth and dry matter accumulation. Greater performance for yield-related traits was obtained with drip irrigation based on crop water requirement for tomato varieties. Examination of plants showed also that local empirical irrigation is responsible for the occurrence of Phytophthora root rot, whereas deficit irrigation proved cause for occurrence of Fusarium wilt (Fusarium oxysporum), blossom end rot and broome rape (Orobanche ramosa) on roots or leaves, stems or fruits.

The experiments on irrigation scheduling with different irrigation systems and strategies gave useful indications on the possibility to improve commercial yield (CY) and water use efficiency. Promising results on CY and agronomical water use efficiency of tomato were achieved with drip irrigation based on crop water requirement, while for the biological water use efficiency higher value was obtained with deficit drip irrigation in both seasons. The findings indicate that the CY was decreased significantly for deficit by 50% in drip irrigation and deficit by 50% in furrow irrigation in both seasons. Mean CY for drip irrigation according to crop water requirement increased by 51% and 56% compared with deficit drip irrigation, whereas furrow irrigation based on crop water requirement increased by 52% and 54% compared with deficit furrow in Experiments 1 and 2, respectively. However, water use efficiency decreased with the increasing water volume.

Simultaneous measurements of rate of photosynthesis based on gas exchange measurements and the thylakoid electron flux based on chlorophyll fluorescence were used to investigate physiological limitations to photosynthesis in leaves of deficit irrigated tomato plants under open field situations. Combined leaf gas exchange/chlorophyll fluorescence measurements differentiated the treatments effectively. Reduction in rate of photosynthesis, stomatal conductance and the maximum quantum efficiency of photosystem II varied across seasons of all varieties, whereas leaf temperature was increased by deficit irrigation in all varieties. Among varieties studied, Miya was found relatively tolerant to deficit irrigation. Stomatal limitation of rate of photosynthesis increased significantly as a result of water stress suggesting a strong influence of the stomatal behaviour.

We also determined the influence of irrigation systems and strategies on water saving and tomato fruit quality. Using deficit drip irrigation was the best management strategy to optimize water use and tomato quality. Fruit dry matter content, acid content and total soluble solids were significantly higher with deficit drip irrigation than with other treatments.

From this thesis it appeared that agro-climatic conditions, access to resources and culture all contribute to the relatively low yields of tomato in the Central Rift Valley of Ethiopia. The thesis also proved that significant advances can be made in yield, quality and resource use efficiency.

The citizen goes shopping : a framework for the assessment and optimization of production from the perspective of society
Michalopoulos, Tassos - \ 2016
Wageningen University. Promotor(en): Alfons Oude Lansink; Michiel Korthals, co-promotor(en): Henk Hogeveen. - Wageningen : Wageningen University - ISBN 9789462579828 - 207
food production - food ethics - labelling - consumer behaviour - consumer preferences - optimization - consumer information - philosophy - political attitudes - animal production - animal ethics - cattle - dairy cattle - voedselproductie - voedselethiek - etiketteren - consumentengedrag - consumentenvoorkeuren - optimalisatie - consumenteninformatie - filosofie - politieke houding - dierlijke productie - dierethiek - rundvee - melkvee

Nowadays, product labels are often used to enable consumers choose products that are friendly to the environment and to animals, natural, healthful and socially responsible. However, certain features of commonly used labels limit their usefulness. This thesis identifies a number of these limitations and presents an innovative labeling approach designed to address them.

More specifically, the following features limit the usefulness of the commonly used “endorsement” labels: they (1) offer a single certification grade, the requirements for which (2) are ‘static’ in the sense that certification standards do not depend on the evolution of the market, (3) are voluntary, and (4) are defined by stakeholders. Consequently, common labels fail to remove information asymmetry regarding the ethical performance of non-certified products; limit the opportunities for moderately –yet positively– concerned consumers to reveal ethical preferences; fail to motivate product improvement beyond certification standard; allow the emergence of a confusing variety of overlapping labels; and allow production stakeholders to resist socially desirable certification requirements when these are unfavorable to their business. In shoft, ethical labels currently fail to unleash on ethical aspects of production the inherently ‘free-market’ dynamics according to which products and firms must continuously innovate and improve, or else become obsolete and vanish.

As an alternative, this thesis proposes and works out an innovative “comparative” labeling approach that is designed to address these limitations. The proposed type of label is (1) multi-grade or continuous, (2) dynamic, (3) mandatory, and (4) society-defined. An example of this type of label is given at Figure 1.

Figure 1: Two variations of an example intuitive color-coded label format. The variations depict different sets of product attributes, and also different aggregation levels of the Environmental Impact attribute.

This type of labeling could motivate the creation of a ‘vitruous cyrcle’ or ‘race to the top’, in which the ethical performance of products moves to the direction that society at large regards as ‘positive’. This process is outlined at Figure 2.

Figure 2: Expected effects on the environmental performance of marketed product substitutes from the introduction of the proposed labeling system, in three phases. In Phase 1, the label is introduced on product substitutes available in the market (supply). In Phase 2, the supply evolves. To the standard (negative) incentives for cost minimization, are now added (positive) incentives to avoid negative reputation and to improve further the environmental frontiers of production through innovation. In Phase 3, the label is adjusted (updated) to the evolved supply. Products that failed to improve since last update might become downgraded (blue arrows).

It is argued that the proposed labeling approach has the potential to boost ethical consumerism as a force for the ethical optimization of the market. This can be directly relevant to issues about which society is concerned, and democratically elected goverments have limited ability to regulate. Among possible uses of the method developed to assess the relative performance of substitute products, are the comparative ranking of presently available labels (so as to inform consumers on the relative impact of different certified products), the justification of the allocation of incentives and discincentives in state policy, and also the ethical optimization and promotion of own production by socially responsible suppliers. Overall, the described approach aspires to transform markets into instruments that work to the direction willed by society, so as to bring market-driven and continuous improvement for production aspects of societal concern, such as environmental and socioeconomic aspects of the real economy.

Optimizing soil and water management in dryland farming systems in Cabo Verde
Santos Baptista Costa, I. Dos - \ 2016
Wageningen University. Promotor(en): Coen Ritsema; Violette Geissen, co-promotor(en): Luuk Fleskens. - Wageningen : Wageningen University - ISBN 9789462577367 - 189
water management - soil management - farming systems - dry farming - optimization - watershed management - watersheds - runoff - erosion control - cape verde - waterbeheer - bodembeheer - bedrijfssystemen - dry farming - optimalisatie - beheer van waterbekkens - stroomgebieden - oppervlakkige afvoer - erosiebestrijding - kaapverdië
Soil and land degradation poses a great challenge for sustainable development worldwide and, in Cabo Verde, has strongly affected both people’s livelihood and the environment. Dryland food production in Cabo Verde faces steep slopes, inadequate practices, irregular intense rain, recurrent droughts, high runoff rates, severe soil erosion and declining soil fertility, leading to the inefficient use of rainwater. Despite the enormous investment in soil and water conservation measures (SWC), land degradation due to water erosion is still rife and dryland crop productivity remains low. Sustainable land management (SLM) techniques that reduce runoff, erosion and nutrient loss are the key to mitigating/preventing land degradation and assuring long-term soil productivity.

This thesis investigated soil and water management techniques for Cabo-Verdean dryland farming systems to increase the efficiency of rainwater and crop yield, combining traditional and scientific knowledge in a field-based participatory approach. Field experiments were conducted in different agro-ecological zones of the Santiago Island aiming to evaluate the effects of water conservation techniques (mulching of crop residue, soil surfactant and pigeon-pea hedges) combined with organic amendments (compost and animal or green manure) on runoff, erosion, soil nutrients and crop yield. The PESERA-DESMICE modelling approach allowed assessing the biophysical and socio-economic benefits of the promising SLM techniques against a local baseline condition and their potential application at larger scale, under climate variability.

Following the general introduction (chapter 1), chapter 2 of the thesis reviews the national strategies towards building resilience against the harsh environmental conditions, analyses the state of land degradation and its drivers, surveys the existing SWC measures, and assesses their effectiveness against land degradation and in supporting people’s livelihoods. The analysis allows inferring that the relative success of Cabo Verde in tackling desertification and rural poverty is due to an integrated governance strategy that comprises awareness raising, institutional framework development, financial resource allocation, capacity building, and active participation of rural communities. The chapter provides a panoramic view of the importance of SWC measures for Cabo Verde drylands and recommends further specific, science-based assessment of the biophysical and socioeconomic impact of SLM and potential for upscaling.

Chapter 3, first, discusses the participatory approach used in selecting the SLM techniques that are field-tested in this research and, then, evaluates the effects of the selected water conservation techniques combined with organic amendments on the generation of runoff and soil loss from rain-fed agricultural fields compared with traditional farmers’ practices. The chapter also discusses the main factors influencing runoff and soil loss in semiarid dryland hilly areas, including the degree of soil cover, rainfall amount and erosivity, slope and soil infiltration rate. Runoff was significantly reduced only with the treatments containing mulch on slopes >10% and in the treatment containing surfactant and organic amendment on slopes <10%. Observed soil erosion rates were highest for the silty-clay-loam soil, followed by the sandy-loam soil and the loamy-soil, reaching a maximum value of 17 Mg ha-1 in the traditional practice, but were reduced by more than 50% with the SLM techniques. Residue mulch and pigeon-pea combined with an organic amendment (T3) almost eliminated runoff and erosion from agricultural fields even on steep slopes, contributing to improved use of rainwater at the plot level. The chapter recommends that SLM techniques, such as T3, be advocated and promoted for the semiarid hillsides of Cabo Verde prone to erosion to increase rainwater-use and to prevent further soil degradation.

As soil erosion, runoff and related nutrient losses constitute a high risk to soil fertility in Cabo Verde drylands, chapter 4 focuses on the effects of the techniques tested in chapter 3 on erosion and runoff related nutrient losses (NO3-N and PO4-P) and on crop productivity. The traditional system lost significantly higher amounts of both NO3-N and PO4-P than the tested SLM techniques, with the T3 technology reducing soil loss, runoff and nutrient losses to nearly a 100%. Nutrient losses from the amended plots were low, while the significant losses from the traditional system could result in long-term nutrient depletion in the soil. The treatments did not consistently increase crop yield or biomass in all three sites, but the combination of organic amendment with soil surfactant increased both crop yield and biomass in some cases. T3 was the best treatment for steep slope areas, although it is crucial to manage the pigeon-pea hedges to achieve higher maize yield. For flatter areas with deeper soils, the combination of organic amendment with soil surfactant could be a less expensive and effective choice. The chapter identifies and recommends SLM techniques to prevent nutrient depletion, improve dryland crop yield and avoid further land degradation due to erosion by water, both in steep slope areas and flatter areas.

Given the potential of the SLM techniques, but also significant spatial-temporal yield variability, chapter 5 considers the PESERA-DESMICE modelling approach to capture a greater range of climatic conditions and evaluate the biophysical and socio-economic benefits of the promising SLM technique (residue mulch combined with pigeon-pea hedges and an organic amendment - T3) against the traditional baseline practice of maize-bean intercropping (T0). It also evaluates the potential for upscaling the selected technique at Island scale. From stations in semi-arid and sub humid climates, long-term historic rainfall statistics allowed construction of 50-year rainfall realizations providing a unique time-series of rainfall scenarios and an envelope of the potential biomass production. T3 elevates yield under both sub-humid and semi-arid climates with greater security for sub-humid areas even though risk of crop failure still exists. The T3 technology offered good potential to increase yields by 20% in 42% of the area and reduce erosion by 8.6 Mg ha-1, but in terms of cost effectiveness, it might be prohibitively expensive for farmers lacking inputs. Such findings can inform policy options or influence adoption of conservation measures under the climatic variability of the Cabo Verde drylands and resilience to future climate change.

The thesis ends with a synthesis chapter (6) that presents the research findings, highlights the new contributions made to the current scientific debates on Climate-Smart Agriculture (CSA) technologies for sub-Saharan Africa, sustainable intensification and land degradation neutrality. The T3 technology can be a promising CSA practice that could be widely used by smallholder farmers in semiarid regions to maintain food production and secure farmers’ livelihoods, while contributing to ecosystem services by storing water in the soil. The synthesis concludes with policy recommendations for optimizing soil and water management on hilly drylands to prevent further degradation.

Hence, the thesis presents options to support moving from degrading and low yielding land management practices towards more sustainable land intensification in hilly drylands that reduce runoff and soil loss, increase crop nutrient and crop productivity, ultimately, contributing to the mitigation/adaptation of climate change, food security and land degradation neutrality in Cabo Verde.

Beheersing emissie grondgebonden kasteelten
Voogt, W. ; Balendonck, J. ; Janse, J. ; Swinkels, G.L.A.M. ; Winkel, A. van - \ 2015
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1363) - 38
teelt onder bescherming - snijbloemen - emissie - beslissingsondersteunende systemen - biologische landbouw - irrigatie - lysimeters - sensors - water - voedingsstoffenbalans - voedingsstoffen - optimalisatie - protected cultivation - cut flowers - emission - decision support systems - organic farming - irrigation - nutrient balance - nutrients - optimization
To make growers to be in control of the emission, a decision support system is developed for irrigation in soil grown crops. In 2013-2014 the implementation was continued and several greenhouse crops were monitored. As was found earlier, the organic greenhouse growers are able to control irrigation in a way that emission is reduced to a minimum. The results obtained at (conventional) flower growers show sometimes high emission of nitrogen. This is due at one hand to high irrigation surpluses but also to high fertilisation of nitrogen. Better tuning of the water- and nitrogen supply to the crop demand is necessary. For these stapes growers need better soil-moisture sensors.
Prototype van een Dynamisch Input Advies Systeem voor biogasinstallaties
Timmerman, M. ; Riel, J.W. van - \ 2015
Wageningen : Wageningen UR Livestock Research (Livestock Research rapport 897) - 58
bio-energie - biogas - gasproductie - co-vergisting - mestvergisting - beslissingsondersteunende systemen - optimalisatie - energieproductie in de landbouw - melkveehouderij - biobased economy - bioenergy - gas production - co-fermentation - manure fermentation - decision support systems - optimization - agricultural energy production - dairy farming
Het Dynamisch Input Advies Systeem (Dynamisch Vergisten) voor biogasinstallaties maakt gebruik van bedrijfsspecifieke procesgegevens voor de dagelijkse bijsturing van de input naar een biogasinstallatie. Het adviessysteem bestaat uit een methodiek die dagelijks de actuele invloed bepaalt van de input op de biogasproductie en een control algoritme die op basis van de relatie tussen de input en de biogasproductie de optimale input bepaalt. Op basis hiervan wordt de input bijgesteld in de richting van de optimale input. Het control algoritme kan worden ingesteld om de input voor de maximaal haalbare biogasproductie te bepalen of om de input te bepalen waarbij het voersaldo (energieopbrengst minus voerkosten) maximaal is. Het doel van het onderzoek was het vaststellen van het “proof of principle” van de methodiek van Dynamisch Vergisten onder praktijkomstandigheden. Het onderzoek heeft plaatsgevonden op een melkveeproefbedrijf en een praktijkbedrijf. Uit de resultaten blijkt dat het principe van Dynamisch Vergisten in staat was om de input zo te sturen dat de biogasproductie toe nam zonder dat het vergistingsproces nadelig werd beïnvloed. De toename in biogasproductie leidde tot hogere voersaldo’s. De methodiek van Dynamisch Vergisten biedt perspectief om het financiële rendement van biogasinstallaties te verbeteren.
Voorsorteren op quotumloos tijdperk
Doornewaard, G.J. - \ 2015
Nieuwsbrief Koeien & Kansen (2015)41. - p. 2 - 2.
melkveehouderij - agrarische bedrijfsvoering - melkproductie - kosten per eenheid - optimalisatie - efficiëntie - melkproductiekosten - melkprijzen - dairy farming - farm management - milk production - unit costs - optimization - efficiency - milk production costs - milk prices
Frank en Ilona Post produceren in Nieuweroord (Drenthe) met 135 koeien bijna 1,2 mln. kg melk op zo’n 44 ha cultuurgrond. Het bedrijf is met ruim 27.000 kg melk per ha behoorlijk intensief. De afgelopen jaren was één van de doelstellingen van de maatschap om de kosten en de financiering per kg melk te verlagen.
Daqu : a traditional fermentation starter in China: microbial ecology and functionality
Zheng, X. - \ 2015
Wageningen University. Promotor(en): Marcel Zwietering; E.J. Smid, co-promotor(en): Rob Nout. - Wageningen : Wageningen University - ISBN 9789462572805 - 175
fermentatieproducten - fermentatie - optimalisatie - starterculturen - micro-organismen - kwaliteit - china - fermentation products - fermentation - optimization - cultured product starters - microorganisms - quality - china
Abstract

Fermented products have high nutritional value and constitute an important part of the Chinese dietary profile; they are also gaining popularity throughout the world. Daqu is a traditional natural fermentation starter culture that has a significant impact on the quality and flavour of Chinese liquor and vinegar.

A review of the literature was conducted focusing on the classification, composition, and manufacture of Daqu. The review provided a preliminary understanding of the link between the fermentation process and the characteristics of the final Daqu product. Then the occurrence, levels, and diversity of microorganisms were studied in different types of Daqu produced by various fermentation processes. The results showed that Bacillus licheniformis and Saccharomycopsis fibuligera were present in all the tested samples of Daqu. Regional comparisons showed Staphylococcus gallinarum and Staphylococcus saprophyticus in southern Daqu. The fungi Sm. fibuligera and Lichtheimia ramosa were found in low/medium-temperature Daqu and Thermomyces lanuginosus occurred in high-temperature Daqu.

In order to study the functionality of Daqu and the contribution of the predominant microorganisms to alcoholic fermentation, the mesophilic and thermophilic bacteria and spores, Enterobacteriaceae, lactic acid bacteria, yeasts, and moulds present in the core and outer portions of Fen-Daqu were isolated. The isolates were identified by culture-dependent sequencing of rRNA genes (16S rRNA for bacteria; 18S rRNA, 26S rRNA, and ITS rRNA for fungi). A succession of fungi, lactic acid, and Bacillus spp. was associated with prevailing acidity, moisture content, and temperature during Daqu fermentation. The predominant species in fermentation were B. licheniformis, Pediococcus pentosaceus, Lactobacillus plantarum, Pichia kudriavzevii, Wickerhamomyces anomalus, Sacchromyces cerevisiae, and Sm. fibuligera.

One strain of the each of the above-mentioned predominant species, with the highest starch degrading ability and alcohol tolerance, was selected and used in different combinations to perform alcoholic fermentation. Metabolite composition differed significantly between various fermentation trials. S. cerevisiae provided superior ethanol production. Sm. fibuligera and B. licheniformis provided the amylolytic activity that converted starch and polysaccharides into fermentable sugars. Finally, W. anomalus was found to be an important contributor to formation of the liquor aroma.

Understanding the microbial diversity and functional activity, as well as the production dynamics and safety of Daqu will enable commercial producers to improve and/or scale-up traditional processes and enhance product quality and safety, thus facilitating entry into international markets.

Economic optimization of surveillance in livestock production chains
Guo, X. - \ 2015
Wageningen University. Promotor(en): Alfons Oude Lansink, co-promotor(en): Helmut Saatkamp; Frits Claassen. - Wageningen : Wageningen University - ISBN 9789462572485 - 180
agrarische economie - optimalisatie - dierziekten - risico - risicobeheersing - gevaren - economie van de veehouderij - vee- en vleesindustrie - agro-industriële ketens - nederland - vee - agricultural economics - optimization - animal diseases - risk - risk management - hazards - livestock economics - meat and livestock industry - agro-industrial chains - netherlands - livestock

Abstract

Hazard surveillance in livestock production chains is an essential activity that is usually conducted by surveillance organizations. Its importance has been highlighted by the major crises that occurred in the field of livestock production and food safety during the last decades. Although extensive research has been conducted to achieve surveillance improvement in livestock production chains, they have limitations in terms of coverage of economic aspects and in the level of detail in modelling the interactions between hazard dynamics and surveillance activities. Hence, the dissertation aims to (1) improve the understanding of hazard surveillance in livestock production chains from an economic perspective, and (2) to apply the obtained knowledge for better model-based in-depth analysis of livestock hazard surveillance.

In this thesis, we first presents a conceptual framework for the economic analysis of single-hazard surveillance systems in livestock production chains which differs from most of the previous research focusing on the technical aspect of livestock hazard surveillance. We conclude that that the conceptual approach is scientifically credible for economic analysis of single-hazard surveillance systems and that the applicability of the approach critically depends on data availability. Then we present a conceptual framework for the economic optimization of a surveillance- portfolio consisting of multiple livestock hazards to survey. This framework applies the portfolio perspective to investigate the surveillance resource allocation problem, which is beyond the state of art that mainly focuses on single hazard surveillance analyses. The credibility and practicability of the framework were also checked.

To demonstrate the usefulness of the developed frameworks, two case studies are conducted. We applied the single-hazard surveillance framework to conduct a comprehensive economic analysis of classical swine fever (CSF) surveillance in the Netherlands. The results of the cost-effectiveness analysis show that the alternative surveillance setups with “PCR on rendered animals” are effective for the moderately virulent CSF strain, whereas the surveillance setups with “routine serology in slaughterhouses” or “routine serology on sow farms” are effective for the low virulent strain. Moreover, the current CSF surveillance system in the Netherlands is cost-effective for both moderately virulent and low virulent CSF strains. The results of the cost-benefit analysis for the moderately virulent CSF strain indicate that the current surveillance system in the Netherlands is adequate. From an economic perspective, there is little to be gained from intensifying surveillance. We also applied the surveillance-portfolio analysis framework to conduct economic optimization of a pig-hazard surveillance-portfolio, consisting of five pig-related hazards, in a Dutch food company. We draw the conclusion that surveillance organizations need to use a portfolio perspective to guide their surveillance resource allocation. This is because the case clearly shows that arbitrarily allocating surveillance resource can cause efficiency losses (either in terms of higher surveillance costs or low SP performance).

Agricultural water productivity optimization for irrigated Teff (Eragrostic Tef) in water scarce semi-arid region of EthiopiaAgricultural water productivity optimization for irrigated Teff (Eragrostic Tef) in water scarce semi-arid region of Ethiopia
Yihun, Y.M. - \ 2015
Wageningen University. Promotor(en): E. Schultz, co-promotor(en): T. Erkossa Jijo; A. Mehari Haile. - Leiden : CRC Press/Balkema - ISBN 9789462571709 - 82
eragrostis tef - waterbeheer - watergebruik - water - watergebruiksrendement - optimalisatie - ethiopië - eragrostis tef - water management - water use - water - water use efficiency - optimization - ethiopia
Optimization-based decision support systems for planning problems in processing industries
Claassen, G.D.H. - \ 2014
Wageningen University. Promotor(en): Jack van der Vorst. - Wageningen : Wageningen University - ISBN 9789462572089 - 171
operationeel onderzoek - logistiek - voedselverwerking - voedselindustrie - pulp- en papierwarenindustrie - beslissingsondersteunende systemen - optimalisatie - procesoptimalisatie - wiskundige modellen - operations research - logistics - food processing - food industry - pulp and paper industry - decision support systems - optimization - process optimization - mathematical models

Summary

Optimization-based decision support systems for planning problems in processing industries

Nowadays, efficient planning of material flows within and between supply chains is of vital importance and has become one of the most challenging problems for decision support in practice. The tremendous progress in hard- and software of the past decades was an important gateway for developing computerized systems that are able to support decision making on different levels within enterprises. The history of such systems started in 1971 when the concept of Decision Support Systems (DSS) emerged. Over the years, the field of DSS has evolved into a broad variety of directions. The described research in this thesis limits to the category of model-driven or optimization-based DSS.

Simultaneously with the emergence of DSS, software vendors recognized the high potentials of available data and developed Enterprise Systems to standardize planning problems. Meanwhile, information oriented systems like MRP and its successors are extended by the basic concepts of optimization based decision support. These systems are called Advanced Planning Systems (APS). The main focus of APS is to support decision making at different stages or phases in the material flow, i.e. from procurement, production, distribution to sales (horizontal-axis), on different hierarchical aggregation levels (vertical-axis) ranging from strategic (long-term) to operational (short- term) planning. This framework of building blocks decomposes planning tasks hierarchically into partial planning problems. This basic architecture of the planning processes in APS is known as the Supply Chain Planning Matrix (SCPM).

Compared to, for instance, discrete parts manufacturing, planning tasks are much more complicated in processing industries due to a natural variation in the composition of raw materials, the impact of processing operations on properties of material flows, sequence dependent change-over times, the inevitable decline in quality of product flows and relatively low margins. These specific characteristics gave rise to focus on optimization-based decision support in the domain of processing industries. The problems to be addressed in this field call for (inter-related) decisions with respect to the required raw materials, the production quantities to be manufactured, the efficient use of available resources, and the times at which raw materials must be available.

Although different APS modules can interact directly, coordination and integration is often restricted to the exchange of data flows between different modules. Given the need for specific integrated decision support, the research presented in this thesis focusses particularly on medium to short term decision support at production stage in processing industry, including the vertical and horizontal integration and coordination with adjacent building blocks in the SCPM.

Extensive reviews from literature show that the gap between research and practice of DSS is widening. As the field of DSS was initiated as an application oriented discipline, the strategy of what is referred to as “application-driven theory” was taken as the preferred approach for this thesis. “Application-driven” refers to a bottom-up approach which means that the relevance of the research should both be initiated and obtained from practice. The intended successful use of the proposed approaches should, where possible, be represented by tests of adequacy. Simultaneously, the contribution to “theory” aims to be a recognizable part of the research effort, i.e.

obtained understanding and insights from problems in practice should provide the basis for new approaches. Based on the preceding considerations we defined the following general research objective:

General research objective

To support medium- to short term planning problems by optimization-based models and solution techniques such that:

i) The applicability and added value of (prototype) systems is recognized and carried by decision makers in practice

ii) The proposed approaches contribute to knowledge, understanding and insights from a model building and solving point of view.

In order to link the general objective with the different studies in the thesis, we defined five, recurring research premises, i.e. Professional relevance and applicability (P1), Aggregation (P2), Decomposition and reformulation (P3), Vertical integration at production level (P4), and Horizontal coordination and integration (P5).

The overarching premise P1 refers to the first part of the research objective. All other premises refer to the second part of the research objective, i.e. model building and/or – solving. Several planning issues are studied to give substance to the research objective and each study is connected to at least two research premises.

Study 1: Planning and scheduling in food processing industry

The main question in Chapter 2 was:” How to apply aggregation, decomposition and reformulation in model-based DSS at planning and scheduling level such that the aspect of decision support is recognized and appreciated by decision makers in practice, and which level of aggregation is needed to integrate production planning (i.e. lot-sizing) and scheduling problems in a single model?

The study consists of two parts. The first part of the study refers to a case study for the bottleneck packaging facilities of a large dairy company. The goal was to develop, implement and test a pilot DSS which was able to deliver solutions recognized and carried by decision makers at lower decision levels. The latter aim implied that a straight-forward aggregation on time, product type, resources or product stage, was not preferred. The key to develop an approach for regular use was to identify and take advantage of specific problem characteristics. Clustering of numerous jobs, while retaining information at order level, could be exploited in a reformulation approach. The inclusion of (combined) generalized- and variable upper bound constraints gave very tight lower bounds and sparse search trees.

An extensive test phase in daily practice showed that the main benefit of the DSS was the initial quality of the generated plans including the time needed to generate these schedules. Hence, decision makers could i) postpone their planning tasks, ii) conveniently cope with rush orders or planned maintenance and iii) easily generate

alternatives or revised plans when unforeseen disturbances occur. Moreover, the graphical presentation and overview of the (future) working schedule enabled order acceptance to make use of remaining capacity.

The study also showed that planning problems in practice cannot be captured exhaustively by a (simplified) model. Decision makers need the opportunity to modify automatically generated plans manually and use human judgement and experience such that the solution is tuned to the actual situation. Hence, the DSS should not be considered as an optimizer but rather as a tool for generating high quality plans to be used for further analysis. Within this context the various options of a user-friendly, graphical, and fully interactive user interface, were of major importance.

Although the case study clearly demonstrates the validity of earlier case based DSS research for current days APS, the proposed approach is hardly a generic solution for a complete vertical integration between lot-sizing and scheduling. If lot-size decisions are strongly affected by the sequence of jobs, production planning and scheduling should be performed simultaneously.

As the described case refers to an earlier study and today’s APS do not provide modules for integrated lot-sizing and scheduling, the second part of the study gives an overview of developments in literature regarding lot-sizing and scheduling models and assess their suitability for addressing sequence-dependent setups, non-triangular setups and product decay. The review shows a tendency in which so-called Big Bucket (BB) models are currently proposed for short term time horizons too. However, we argue that segmentation of the planning horizon is a key issue for simultaneous lot-sizing and scheduling. The advantage of BB models may become a major obstacle for i) the effectiveness of simultaneous lot-sizing and scheduling, and ii) addressing specific characteristics in food processing industry.

Study 2: Vertical integration of lot-sizing and scheduling in food processing industry

Chapter 3 focused on a complete integration of lot-sizing and scheduling decisions in a single model. The main question was:” How to integrate production planning (i.e. lot- sizing) and scheduling problems in a single model, such that common assumptions regarding the triangular setup conditions are relaxed and issues of product decay and limited shelf lives are taken into account?”

The literature research in Chapter 2 revealed that the computational advantage of time oriented aggregation in BB models may become a major obstacle in addressing the identified characteristics in FPI. In addition, product decay is primarily associated with the “age” of products and consequently relates to the segmentation of the time- horizon. Therefore, two SB models are developed to demonstrate the impact of non- triangular setups and product decay on the generated solutions. Small scale examples were used to demonstrate how a small change in the balance between inventory - and

changeover costs may generate significantly different solutions, especially when the triangular setup conditions do not hold.

The developed models are potentially very large formulations and, as expected, hard to solve. Exploratory research was conducted with a Relax-and-Fix (R&F) heuristic. The heuristic is based on a decomposition of the time horizon. Numerical results of small to medium sized problem instances are promising. However, solving real-size problem instances is not possible yet.

Study 3: Integrated planning between procurement and production

The case study in Chapter 4 focussed on the need for horizontal coordination and integration between the phases procurement and production, which is of particular importance in inter-organizational supply chains. The main question was:” How to model and solve an integrated planning problem between procurement and production, both on a mid-term and short-term planning level, in an inter-organizational supply chain? The research question was projected on an illustrative milk collection problem in practice.

The aim was to develop a pilot DSS that lifted decision support for a “weaker” partner in a food supply chain to a higher level, and to illustrate the importance of horizontal integration between the phases procurement and production in an APS framework.

Problem analysis revealed that the problem can be classified as an extension of the Periodic Vehicle Routing Problem (PVRP). The problem was decomposed into more tractable sub problems on different hierarchical levels, i.e. the daily (vehicle) routing problem was separated from a medium-term planning problem. On the higher planning level, numerous suppliers were aggregated such that total supply within a cluster met (multiple) vehicle loading capacities. The continuous supply of relatively small amounts from many suppliers had to be balanced with strict delivery conditions at processing level. A model was developed to assign a single (stable) collection rhythm to each cluster such that the total, weighted deviation of desired processing levels on various days in the planning horizon was minimized.

The applied aggregation on the higher planning level turned out to be very beneficial for the required disaggregation at the lower planning level. Once supplier farms were geographically grouped into clusters and the aggregated supply within a cluster was assigned to a single collection rhythm with fixed collection days, the (initial) daily routing problem was considerably easier to solve for vehicle schedulers.

The computational complexity of the problem was reduced by exploiting application-based properties algorithmically in a specific branch-and-bound scheme, i.e. a customized approach of Special Ordered Sets type 1 (SOS1) This approach made it possible to solve the generated problems exactly for real-size problem instances.

The various facilities of a user-friendly and interactive man-machine interface (i.e. an input, planning, simulation and analysing module) turned out to be essential. Decision makers could easily change the data, and the generated plans, in a separate simulation module. However, the impact of any modification was immediately visualised by several (conflicting) indicators in the output screens, both on supply and demand level.

Study 4: Mixed Integer (0-1) Fractional Programming in Paper Production Industry

The study in Chapter 5 focussed on the impact of technical settings of production units on material flows. The main question was:” How to support decision-makers in practice if crucial properties of end products simultaneously depend on (endogenous) types of raw materials with different chemical or physical properties and (endogenous) technical settings of processing units?

The goal of the study was to revise and upgrade an existing, locally used DSS, to a tailored and flexible tool for decision support within the enterprise. The study revealed that the aimed extension towards multi-objective decision support, together with new physical insight for calculating properties of end products due to process operations, had a substantial impact on the optimization module.

The proposed solution procedure takes advantage of the problem characteristics and gives rise i) to apply and extend a classical reformulation approach for continuous linear fractional programming (FP) problems to a more general class of mixed integer (binary) FP problems and ii) to exploit the special structure between the original non- linear mixed integer model and the continuous, linear reformulation by applying the concept of Special Ordered Sets type 1 (SOS1).

Although Chapter 5 focusses in particular on the reformulation and solution approach, the DSS consists of four main building blocks, i.e. the user interface, a scenario manager, a simulation- and optimization routine. The optimization module provides a powerful tool to find feasible solutions and the best (unexpected) recipes for any available set of raw materials. Moreover, it provides an innovative way of decision support for purchasing (new) pulps on the market, for assigning available pulps to different paper grades, and for attuning available stock levels of raw materials to (changing) production targets for different paper grades. The results of the optimization routine are mainly used to obtain alternative recipes for different paper grades. Usually, these recipes are stored as base scenarios and adapted to daily practice in the simulation module.

Main conclusions and future research

Based on the studies in the Chapters 2 and 3 we conclude that no generically applicable models and/or solution approaches exist for simultaneous planning and scheduling in processing industries. More industry-specific solutions are needed incorporating specificities of different production environments into those models. The key to develop solvable approaches for contemporary practice may be i) to use knowledge and experience from practice and take advantage of specific characteristics in different problem domains during model construction, and/or ii) to identify and exploit special problem structures for solving the related models.

We conclude that surprisingly little research has been devoted to issues of coordination and integration between “procurement” and “production”. The studies in the chapters 4 and 5 confirm that sourcing of (raw) materials flows needs more attention in processing industries, particularly in push-oriented, inter-organizational networks. The valorisation of raw materials can be improved even more if the composition of raw materials is considered too in future planning problems at production level.

In the second part of this thesis we focused on extensions for the applicability of Special Ordered Sets type 1 (SOS1), both from an algorithmic (Chapter 4) and modelling (Chapter 5) point of view. We conclude that the concept of SOS1 can extend a classical reformulation approach for continuous fractional programming (FP) problems, to a specific class of mixed integer (0-1) FP problems. Moreover, we conclude that a natural ordering of the variables within the sets is not necessary to make their use worthwhile. A separate (user defined) reference row or weights associated to the variables in the sets might be omitted for an efficient use of SOS1 in commercially available mathematical programming packages. However, this requires further research and extensive computational tests.

Proceedings of the XII Global Optimization Workshop, Mathematical and Applied Global Optimization, MAGO 2014
Casado, L.G. ; García, I. ; Hendrix, E.M.T. - \ 2014
Almería : Universidad de Almería - ISBN 9788416027576 - 164
optimalisatie - wiskunde - optimization - mathematics
Vroege detectie van dracht bij koeien door Proteomics Biomerkers in melk = Early pregnancy detection using proteomics biomarkers in milk
Pas, M.F.W. te; Kruijt, L. ; Wit, A.A.C. de; Hulsegge, B. ; Riel, J.W. van; Heeres-van der Tol, J.J. ; Sulkers, H. ; Woelders, H. - \ 2014
Lelystad : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research nr. 747) - 10
melkkoeien - zwangerschap - eiwitexpressieanalyse - merkers - melkproductie - melkveehouderij - rundveehouderij - productiebeperkingen - optimalisatie - voortplantingsefficiëntie - dairy cows - pregnancy - proteomics - markers - milk production - dairy farming - cattle husbandry - production restrictions - optimization - reproductive efficiency
The aim of this study is to develop an accurate, fast, cheap, and reliable test to detect pregnancy before day 35 on the basis of markers in milk. The ultimate goal is to have a method that can be implemented in a practical setting.
Perspectief inlandse teelt eiwithoudende gewassen voor de mengvoederindustrie
Mheen, H.J.C.J. van der; Timmer, R.D. - \ 2013
Kennisakker.nl 2013 (2013)11 dec.
akkerbouw - glycine soja - glycine (fabaceae) - eiwitleverende planten - peulvruchten - opbrengst - rentabiliteit - optimalisatie - prijsvorming - erwten - vicia faba - arable farming - protein plants - grain legumes - outturn - profitability - optimization - price formation - peas
In 2011 en 2012 is door PPO, in opdracht van het Productschap Akkerbouw, een 2-jarig onderzoek uitgevoerd waarbij de teelttechnische aspecten en de gewasproductie van een zevental eiwithoudende gewassen in twee Nederlandse teeltgebieden (Zuidoostelijk- en Noordoostelijk zandgebied) werden onderzocht.
Kan de verdeling van biologische bestrijders beter?
Os, E.A. van - \ 2013
glastuinbouw - kasgewassen - organismen ingezet bij biologische bestrijding - optimalisatie - plantenplagen - toepassing - methodologie - ziektebestrijding - sensors - greenhouse horticulture - greenhouse crops - biological control agents - optimization - plant pests - application - methodology - disease control
Poster met informatie over optimalisatie van de verdeling van biologische bestrijders in kassen. Waarbij aandacht voor de methode van doseren van biologische bestrijders, ziektedetectie en aanpassing van de doseerhoeveelheid aan de plek van de plaag en de plantgrootte en beslissen hoeveel en waar bestrijders moeten worden uitgezet.
Efficiëntie van de fotosynthese kan met een factor tien omhoog : plant gaat slordig om met zonne-energie
Klein Lankhorst, R.M. ; Kierkels, T. ; Heuvelink, E. - \ 2013
Onder Glas 10 (2013)4. - p. 44 - 45.
zonne-energie - glastuinbouw - teelt onder bescherming - plantenontwikkeling - fotosynthese - lichtrelaties - optimalisatie - landbouwkundig onderzoek - biobased economy - solar energy - greenhouse horticulture - protected cultivation - plant development - photosynthesis - light relations - optimization - agricultural research
Een plant gaat bijzonder slordig om met zonne-energie. Hij vertaalt slechts 0,5% van de opgevangen energie in biomassa. Voor de plant zelf is dat genoeg, voor ons niet. Als je de fotosynthese-efficiëntie weet te verbeteren, kan de (voedsel) productie enorm omhoog. Daar wordt nu hard aan gewerkt binnen het project BioSolar Cells.
One size fits all? : optimization of rainbow trout breeding program under diverse preferences and genotype-by-environment interaction
Sae-Lim, P. - \ 2013
Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Hans Komen; A. Kause. - S.l. : s.n. - ISBN 9789461734648 - 200
regenboogforel - dierveredeling - veredelingsprogramma's - genotype-milieu interactie - optimalisatie - kenmerken - genetische winst - selectief fokken - simulatie - visteelt - aquacultuur - rainbow trout - animal breeding - breeding programmes - genotype environment interaction - optimization - traits - genetic gain - selective breeding - simulation - fish culture - aquaculture

Global fish breeders distribute improved animal material to several continents to be farmed under diverse environments, and for very different market conditions. When establishing a global breeding program, there is a need to assess whether or not a single breeding objective satisfies the markets across different countries. It may be challenging to develop a single fish stock that performs well across all environments due to genotype-by-environment interaction (GxE). GxE is a phenomenon describing the possibility that different genotypes have a different sensitivity to changes in an environment. The objective of this thesis was to develop an optimized global breeding program for rainbow trout (Oncorhynchus mykiss) in terms of a balanced breeding goal that satisfies preferences of trout producers and maximized genetic gains across environments in the presence of GxE in production traits. Analytic hierarchy process (AHP) was used to estimate preferences, which can be aggregated to consensus preference values using weighted goal programming (WGP). The analysis revealed that the 6 most important traits were thermal growth coefficient (TGC), survival (Surv), feed conversion ratio (FCR), condition factor (CF), fillet percentage (FIL%), and late maturation (LMat). Individual trait preferences are different for farmers having different farming environments and producing different end-products. Calculating consensus preference values resulted in consensus desired genetic gains. To satisfy most farmers, consensus desired genetic gains can be taken into account in a global breeding strategy. Strong genotype re-ranking was found for all growth traits across environments. Based on simulation, re-location of breeding program led to highest total genetic gain for body weight at harvest. Alternatively, including sib performance into selection index increased genetic gain in all environments. Finally, environment-specific program can be used, but this is costly. There is a possibility of a conflict between 2 profits: from a breeding company and fish farmers and an optimum solution for that conflict can be found by using macroeconomics and cost-benefit analysis.

tapsgewijs ontwerpen : nieuwe methodiek voor het ontwerpen van teeltsystemen met de Chrysantenteelt als voorbeeld
Jansen, M. ; Vermeulen, T. ; Blok, C. ; Khodabaks, M.R. - \ 2012
Wageningen : Wageningen UR Glastuinbouw - 16
chrysanthemum - teeltsystemen - innovaties - energiebesparing - emissiereductie - optimalisatie - methodologie - substraten - kweekmedia - alternatieve methoden - cropping systems - innovations - energy saving - emission reduction - optimization - methodology - substrates - culture media - alternative methods
Het ontwerpen van een geheel nieuw teeltsysteem is complex. Het samenspel tussen levende organismen, techniek, voedingssturing en plantgezondheid maakt de ontwikkeling lastig. Toch zijn er voldoende redenen om nieuwe teeltsystemen te ontwikkelen. Voorbeelden hiervan zijn energiegebruik en de noodzaak om te komen tot een nagenoeg emissieloze tuinbouw in 2027. Deze laatste vergt alternatieven voor de huidige grondgebonden teeltwijze. Naast de ‘bovengrondse’ eisen voor het teeltsysteem zijn hier vooral de ‘ondergrondse’ voorwaarden cruciaal in het ontwerpproces. De geschiedenis leert dat juist hier veel fouten gemaakt worden. Het valt ook niet mee om een verregaand gemechaniseerde en kostenefficiënte teelt zoals de chrysantenteelt over te zetten op een nieuw teeltsysteem. Al sinds de jaren ‘70 zijn er onderzoeken gedaan om te komen tot een nieuw systeem. Hier en daar zijn kleine successen gehaald maar tot een doorbraak is het nog niet gekomen. Het ontwerpproces moest daarom onder de loep.
Verbetering spuittechniek in de teelt van potplanten
Staaij, M. van der; Weel, P.A. van; Hamelink, R. - \ 2012
Bleiswijk : Wageningen UR Glastuinbouw (Rapporten GTB 1207) - 36
spuiten - verbetering - technieken - glastuinbouw - potplanten - vergelijkingen - teeltsystemen - optimalisatie - nederland - spraying - improvement - techniques - greenhouse horticulture - pot plants - comparisons - cropping systems - optimization - netherlands
In de teelt van potplanten is spuittechniek een belangrijk aandachtspunt. Twee type potplantenbedrijven zijn te onderscheiden: teelten op de grond/betonvloer (vaste teelten) of op rolcontainers (mobiele teelten). Beide typen vragen om een verschillende aanpak. Potplanten op rolcontainer (Calathea): Voor potplanten op rolcontainers (mobiele teelt) werden een spuitboom met luchtondersteuning, het Hoge Druk Systeem van Arend-Sosef en het Pieton Systeem van Van der Ende Pompen vergeleken met een conventionele spuitboom. De bedekking van de onderkant van de bladeren verbeterde bij alle spuitconfiguraties t.o.v. de conventionele spuitboom. De percentages bedekking liepen op van 15 naar 30 procent bij grote planten van 50 cm hoogte tot 60 procent op kleine planten van 30 cm hoog. Het heen en weer spuiten leverde bij alle methoden een verbetering van 7 tot 14 procent op t.o.v. een enkelvoudige bespuiting. Hierbij moet worden aan getekend dat dit alleen in grote planten is uitgevoerd. Tijdens de proeven werd stekend gespoten onder een hoek van 45°. Bij grote planten bleek deze hoek te groot. De wolk druppeltjes rolde over het gewas heen in plaats van er doorheen. Verkleinen van de hoek naar 35° en 25° gaf een verbetering van de bedekking van de onderkant van de bladeren. Potplanten op betonvloeren (Bananenplanten): Voor potplanten op beton vloeren (vaste teelt) werden aan een conventionele spuitboom spuitlansen met elk twee spuitkopjes gemonteerd. Met de spuitlansen werd van onderaf in het gewas gespoten (onderdoor spuiten). Met een conventionele spuitboom werd een bedekkingspercentage op de onderkant van de bladeren behaald van 0,5 tot 5 procent. Met het onderdoor-spuiten werden bedekkingspercentages behaald tot 50 procent. Abstract Spraying techniques are a major concern in the cultivation of potted plants. Two types of potted plant cultivation can be distinguished: crops on the ground / concrete floor (immobile culture), or crops on roll containers (mobile culture). Each type requires a different approach. Pot plants on a mobile container (Calathea): For pot plants in mobile containers (mobile culture), two spraybars with air support, were compared to a conventional spraybar. The spraybars with air support were the high pressure system from Arend-Sosef and the Pieton system from Van der Ende Pumps. The deposition of liquid on the untherside of the leaves increased with with both spraybars compared to the conventional spraybar. The coverage rates rose from 15 to 30% for large plants (50 cm high) to 60% for small plants (30 cm high). Spraying back and forth improved coverage by 7 to 14% for all methods compared to a single spraying. It should be noted that this was only performed with large plants. The spray was applied at an angle of 45 degrees during the trials, however this angle was to large for large plants. The droplets passed over the crop, rather than through it. Reduction of the angle to 35 and 25 degrees improved the deposition on the untherside of the leaves. Pot on concrete floors (Banana Plants): For potted plants on concrete floors (immobile culture) spraylances with two spray nozzles were added to a conventional spraybar. The crop was sprayed from below (spraying underneath) with the lances. The covered area on the untherside of the leaves was 0.5 to 5% with the conventional spraybar, whereas the coverage percentages achieved went up to 50% by spraying from below.
Modelling and optimization of the downstream processing of microalgal biomass to biodiesel
Koetzier, B.J. ; Slegers, P.M. ; Boxtel, A.J.B. van - \ 2012
algen - productieprocessen - biodiesel - modellen - optimalisatie - biomassaconversie - biobased economy - algae - production processes - models - optimization - biomass conversion
Poster met onderzoeksinformatie.
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