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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Robotic-cell scheduling with pick-up constraints and uncertain processing times
Tonke, Daniel ; Grunow, Martin ; Akkerman, Renzo - \ 2019
IISE Transactions 51 (2019)11. - ISSN 2472-5854 - p. 1217 - 1235.
automated manufacturing equipment - cyclic scheduling - optimization - Robotic-cell scheduling - uncertainty

Technological developments have propelled the deployment of robots in many applications, which has led to the trend to integrate an increasing number of uncertain processes into robotic and automated equipment. We contribute to this domain by considering the scheduling of a dual-gripper robotic cell. For systems with one potential bottleneck, we determine conditions under which the widely used swap sequence does not guarantee optimality or even feasibility and prove that optimal schedules can be derived under certain conditions when building on two types of slack we introduce. With the addition of a third type of slack and the concept of fixed partial schedules, we develop an offline-online scheduling approach that, in contrast with previous work, is able to deal with uncertainty in all process steps and robot handling tasks, even under pick-up constraints. The approach can deal with single- or multiple-bottleneck systems, and is the first approach that is not restricted to a single predefined sequence such as the swap sequence. Our approach is well suited for real-world applications, since it generates cyclic schedules and allows integration into commonly-used frameworks for robotic-cell scheduling and control. We demonstrate the applicability of our approach to cluster tools in semiconductor manufacturing, showing that our approach generates feasible results for all tested levels of uncertainty and optimal or near-optimal results for low levels of uncertainty. With additional symmetry-breaking constraints, the model can be efficiently applied to industrial-scale test instances. We show that reducing uncertainty to below 10% of the processing time would yield significantly improved cycle lengths and throughput. We also demonstrate that the widely used swap sequence only finds solutions for less than 1% of the instances when strict pick-up constraints are enforced and processing times are heterogeneous. As our approach finds feasible solutions to all of these instances, it enables the application of robotic cells to a significantly broader application environment.

Optimizing ex situ genetic resource collections for European livestock conservation
Oliveira Silva, Rafael De; Ahmadi, Bouda Vosough ; Hiemstra, Sipke Joost ; Moran, Dominic - \ 2019
Journal of Animal Breeding and Genetics 136 (2019)1. - ISSN 0931-2668 - p. 63 - 73.
cryoconservation - ex situ conservation - gene bank - livestock diversity - optimization

Ex situ collections offer the potential to reduce extinction risks, affording option to society in maintaining future breeding opportunities for productivity and heritage traits. However, how much should we be seeking to collect and conserve in gene banks, and where? We developed a mathematical model to optimize logistical decisions of breed conservation choices and to evaluate alternative scenarios for efficiently re-allocating genetic materials currently stored in different European gene banks, allowing for cross-country collections, cost and cryogenic capacity differentials. We show how alternative allocations for the breeds that are currently stored in 11 European gene banks could reduce overall conservation costs by around 20% by selecting cryogenic banks that have relatively lower combination of fixed and collection costs, and are geographically closer to collection regions. Our results show that centralizing collections in one gene bank would double the costs, relative to collective European collections approaches. We also calculate marginal costs of collections and show that increasing diversity within the gene banks implies in higher costs per conserved breed.

Selection of fractionation pathways and intermediates for mixed consumer products
Castiglioni, Alberto ; Jonkman, Jochem ; Akkerman, Renzo ; Padt, Albert van der - \ 2018
In: Computer Aided Chemical Engineering. - Elsevier B.V. (Computer Aided Chemical Engineering ) - ISBN 9780444642356 - p. 651 - 656.
mild fractionation - optimization - process selection - product selection

Mixed consumers products, such as cosmetics and foods, normally consist of a mixture of intermediates. Most of these intermediates are currently produced by fractionation, a rather complex process where multiple intermediates are obtained from a single raw material, often focused on high purity. These intermediates can subsequently be combined to satisfy demand and quality requirements. The chemical purity of intermediates is, however, not always necessary, and mild fractionation of raw materials is often sufficient. Therefore, we propose an optimization-based decision support framework to select cost-efficient fractionation pathways and intermediates. We illustrate our approach for the processing of lupin seeds and yellow peas, and investigate mild fractionation as a more resource-efficient way of producing intermediates for mixed consumer products. The results show that, if only few intermediates are used, high purity is needed to comply with the quality requirements of a broad range of final applications. If more intermediates can be used, mildly refined intermediates can be selected to cover the demand of a part of the products with resource savings. In our illustrative case, using eight instead of four intermediates leads to water and energy reduction of about 29 % and 28 %, respectively. In general, our results indicate that using fractionation pathways leading to intermediates with lower purity provides opportunities for more resource-efficient production, and similar opportunities are expected to exist in integrated product and process design for other mixed consumer products.

Effects of macro and micronutrients on neutral lipid accumulation in oleaginous microalgae
Ghafari, Mohsen ; Rashidi, Behzad ; Haznedaroglu, Berat Zeki - \ 2018
Biofuels 9 (2018)2. - ISSN 1759-7269 - p. 147 - 156.
lipid accumulation - macronutrients - micronutrients - Oleaginous microalgae - optimization
In this study, effects of key macro and micronutrients on neutral lipid accumulation of six oleaginous microalgae species were investigated. For each nutrient, three different concentrations (0.5×, 1×, and 2×) were tested individually and compared to the most commonly utilized growth medium recipes. Neutral lipid accumulation was quantified using specific nonpolar dyes with long-wavelength absorption and fluorescence. Tested microalgae species showed different lipid accumulation responses to changes in nutrient concentrations. Optimum concentrations of nutrients were selected for each species based on either the most lipid productive case or no significant difference to the lipid contents. Selected optimal conditions were also validated where Chlorella sorokiniana, Chlorella vulgaris, Dunaliella tertiolecta, and Tetraselmis suecica showed 4, 10, 34, and 39% higher lipid productivities per unit volume, respectively. Botryococcus sudeticus and Ettlia oleoabundans did not show improved lipid productivities. Extensive optimization of macro and micronutrient concentrations offers several benefits of decreased material inputs and waste generation, improved biomass productivity, and overall cost savings.
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.

Efficient and economical way of operating a recirculation aquaculture system in an aquaponics farm
Karimanzira, Divas ; Keesman, Karel ; Kloas, Werner ; Baganz, Daniela ; Rauschenbach, Thomas - \ 2017
Aquaculture Economics & Management 21 (2017)4. - ISSN 1365-7305 - p. 470 - 486.
Aquaponics - dynamic modeling - economics - optimization
In this article, optimal control methods based on a metabolite-constrained fish growth model are applied to the operation of fish production in an aquaponic system. The system is formulated for the twin objective of fish growth and plant fertilization to maximize the benefits by optimal and efficient use of resources from aquaculture. The state equations, basically mass balances, required by the optimization algorithms are given in the form of differential equations for the number of fish in the stock, their average weight as mediated through metabolism and appetite, the water recirculation and waste treatment, hydroponic nutrient requirements and their loss functions. Six parameters, that is, water temperature, flow rate, stock density, feed ration size per fish, energy consumption rate and the quality of food (percentage of digestible proteins) are used to control the system under dynamic conditions. The time to harvest is treated as a static decision variable that is repeatedly adjusted to find the profit-maximizing solution. By modeling the complex interactions between the economic and biological systems, it is possible to obtain the most efficient decisions with respect to diet composition, feeding rates, harvesting time and nutrient releases. Some sample numerical results using data from a tilapia-tomato farm are presented and discussed.
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.

A meta-analysis of leaf nitrogen distribution within plant canopies
Hikosaka, Kouki ; Anten, Niels P.R. ; Borjigidai, Almaz ; Kamiyama, Chiho ; Sakai, Hidemitsu ; Hasegawa, Toshihiro ; Oikawa, Shimpei ; Iio, Atsuhiro ; Watanabe, Makoto ; Koike, Takayoshi ; Nishina, Kazuya ; Ito, Akihiko - \ 2016
Annals of Botany 118 (2016)2. - ISSN 0305-7364 - p. 239 - 247.
Canopy photosynthesis - functional group - leaf area index - light distribution - light extinction coefficient - model - nitrogen allocation - nitrogen use - optimization

Background and aims Leaf nitrogen distribution in the plant canopy is an important determinant for canopy photosynthesis. Although the gradient of leaf nitrogen is formed along light gradients in the canopy, its quantitative variations among species and environmental responses remain unknown. Here, we conducted a global meta-analysis of leaf nitrogen distribution in plant canopies. Methods We collected data on the nitrogen distribution and environmental variables from 393 plant canopies (100, 241 and 52 canopies for wheat, other herbaceous and woody species, respectively). Key Results The trends were clearly different between wheat and other species; the photosynthetic nitrogen distribution coefficient (Kb) was mainly determined by leaf area index (LAI) in wheat, whereas it was correlated with the light extinction coefficient (KL) and LAI in other species. Some other variables were also found to influence Kb. We present the best equations for Kb as a function of environmental variables and canopy characteristics. As a more simple function, Kb = 0·5KL can be used for canopies of species other than wheat. Sensitivity analyses using a terrestrial carbon flux model showed that gross primary production tended to be more sensitive to the Kb value especially when nitrogen content of the uppermost leaf was fixed. Conclusion Our results reveal that nitrogen distribution is mainly driven by the vertical light gradient but other factors such as LAI also have significant effects. Our equations contribute to an improvement in the projection of plant productivity and cycling of carbon and nitrogen in terrestrial ecosystems.

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.

Sampling design optimization of a wireless sensor network for monitoring ecohydrological processes in the Babao River basin, China
Ge, Y. ; Wang, J.H. ; Heuvelink, G.B.M. ; Jin, R. ; Li, X. ; Wang, J.F. - \ 2015
International Journal of Geographical Information Science 29 (2015)1. - ISSN 1365-8816 - p. 92 - 110.
linear model of coregionalization - optimization - spatial simulated annealing - universal cokriging

Optimal selection of observation locations is an essential task in designing an effective ecohydrological process monitoring network, which provides information on ecohydrological variables by capturing their spatial variation and distribution. This article presents a geostatistical method for multivariate sampling design optimization, using a universal cokriging (UCK) model. The approach is illustrated by the design of a wireless sensor network (WSN) for monitoring three ecohydrological variables (land surface temperature, precipitation and soil moisture) in the Babao River basin of China. After removal of spatial trends in the target variables by multiple linear regression, variograms and cross-variograms of regression residuals are fit with the linear model of coregionalization. Using weighted mean UCK variance as the objective function, the optimal sampling design is obtained using a spatially simulated annealing algorithm. The results demonstrate that the UCK model-based sampling method can consider the relationship of target variables and environmental covariates, and spatial auto- and cross-correlation of regression residuals, to obtain the optimal design in geographic space and attribute space simultaneously. Compared with a sampling design without consideration of the multivariate (cross-)correlation and spatial trend, the proposed sampling method reduces prediction error variance. The optimized WSN design is efficient in capturing spatial variation of the target variables and for monitoring ecohydrological processes in the Babao River basin.

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.

Wat zijn de laatste inzichten uit onderzoek rondom biggenopfok
Hoofs, Anita - \ 2015
pig farming - piglets - animal health - feed intake - optimization - returns - farm management - animal welfare - pig housing - animal housing - animal production
Fourier transform assisted deconvolution of skewed peaks in complex multi-dimensional chromatograms
Hanke, A.T. ; Verhaert, P.D.E.M. ; Wielen, L.A.M. van der; Eppink, M.H.M. ; Sandt, E.J.A.X. ; Ottens, M. - \ 2015
Journal of Chromatography. A, Including electrophoresis and other separation methods 1394 (2015). - ISSN 0021-9673 - p. 54 - 61.
multivariate curve resolution - purification process-development - ion-exchange chromatography - multicomponent chromatograms - liquid-chromatography - automatic program - parameters - optimization - algorithms - equations
Lower order peak moments of individual peaks in heavily fused peak clusters can be determined by fitting peak models to the experimental data. The success of such an approach depends on two main aspects: the generation of meaningful initial estimates on the number and position of the peaks, and the choice of a suitable peak model. For the detection of meaningful peaks in multi-dimensional chromatograms, a fast data scanning algorithm was combined with prior resolution enhancement through the reduction of column and system broadening effects with the help of two-dimensional fast Fourier transforms. To capture the shape of skewed peaks in multi-dimensional chromatograms a formalism for the accurate calculation of exponentially modified Gaussian peaks, one of the most popular models for skewed peaks, was extended for direct fitting of two-dimensional data. The method is demonstrated to successfully identify and deconvolute peaks hidden in strongly fused peak clusters. Incorporation of automatic analysis and reporting of the statistics of the fitted peak parameters and calculated properties allows to easily identify in which regions of the chromatograms additional resolution is required for robust quantification.
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
The time-dependent two-echelon capacitated vehicle routing problem with environmental considerations
Soysal, M. ; Bloemhof, J.M. ; Bektas, T. - \ 2015
International Journal of Production Economics 164 (2015). - ISSN 0925-5273 - p. 366 - 378.
road freight transportation - city logistics - emission - optimization - models - algorithm - windows - impact - costs
Multi-echelon distribution strategies in which freight is delivered to customers via intermediate depots rather than direct shipments is an increasingly popular strategy in urban logistics. This is primarily to alleviate the environmental (e.g., energy usage and congestion) and social (e.g., traffic-related air pollution, accidents and noise) consequences of logistics operations. This paper presents a comprehensive MILP formulation for a time-dependent two-echelon capacitated vehicle routing problem (2E-CVRP) that accounts for vehicle type, traveled distance, vehicle speed, load, multiple time zones and emissions. A case study in a supermarket chain operating in the Netherlands shows the applicability of the model to a real-life problem. Several versions of the model, each differing with respect to the objective function, are tested to produce a number of selected key performance indicators (KPIs) relevant to distance, time, fuel consumption and cost. The paper offers insight on economies of environmentally-friendly vehicle routing in two-echelon distribution systems. The results suggest that an environmentally-friendly solution is obtained from the use of a two-echelon distribution system, whereas a single-echelon distribution system provides the least-cost solution.
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