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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Using yield gap analysis to give sustainable intensification local meaning
Silva, João Vasco - \ 2017
University. Promotor(en): Martin van Ittersum, co-promotor(en): Ken Giller; Pytrik Reidsma. - Wageningen : Wageningen University - ISBN 9789463437141 - 361
crops - yields - crop yield - modeling - simulation models - cereals - farming systems - yield losses - gewassen - opbrengsten - gewasopbrengst - modelleren - simulatiemodellen - graansoorten - bedrijfssystemen - oogstverliezen

Yield gap analysis is useful to understand the relative contribution of growth-defining, -limiting and -reducing factors to actual yields. This is traditionally performed at the field level using mechanistic crop growth simulation models, and directly up-scaled to the regional and global levels without considering a range of factors intersecting at farm and farming system levels. As an example, these may include farmers' objectives and resource constraints, farm(er) characteristics, rotational effects between subsequent crops or decisions on resource allocation and prioritization of crop management. The objective of this thesis is to gain insights into yield gaps from a farm(ing) systems perspective in order to identify opportunities for sustainable intensification at local level.

Three contrasting case studies representing a gradient of intensification and capturing a diversity of agricultural systems were selected for this purpose, namely mixed crop-livestock systems in Southern Ethiopia, rice based-farming systems in Central Luzon (Philippines) and arable farming systems in the Netherlands. A theoretical framework combining concepts of production ecology and methods of frontier analysis was developed to decompose yield gaps into efficiency, resource and technology yield gaps. This framework was applied and tested for the major crops in each case study using crop-specific input-output data for a large number of individual farms. In addition, different statistical methods and data analyses techniques were used in each case study to understand the contribution of farmers' objectives, farm(er) characteristics, cropping frequency and resource constraints to yield gaps and management practices at crop level.

Yield gaps were largest for maize and wheat in Southern Ethiopia (ca. 80\\\\% of the water-limited yield), intermediate for rice in Central Luzon (ca. 50\\\\% of the climatic potential yield) and smallest for the major arable crops in the Netherlands (ca. 30\\\\% of the climatic potential yield). The underlying causes of these yield gaps also differed per case study. The technology yield gap explained most of the yield gap observed in Southern Ethiopia, which points to a lack of adoption of technologies able to reach the water-limited yield. The efficiency yield gap was most important for different arable crops in the Netherlands, which suggests a sub-optimal timing, space and form of the inputs applied. The three intermediate yield gaps contributed similarly to the rice yield gap in Central Luzon meaning that sub-optimal quantities of inputs used are as important in this case study as the causes mentioned for the other case studies.

Narrowing the yield gap of the major crops does not seem to entail trade-offs with gross margin per unit land in each case study. However, the opposite seems to be true for N use efficiency and labour productivity particularly in Southern Ethiopia and Central Luzon, and to a less extent in the Netherlands. This means that (sustainable) intensification of smallholder agriculture in the tropics needs to go hand-in-hand with agronomic interventions that increase land productivity while ensuring high resource use efficiency and with labour-saving technologies that can reduce the drudgery of farming without compromising crop yields.

Other insights at farm(ing) system level were clearer in Southern Ethiopia than in Central Luzon or in the Netherlands. For example, alleviating capital constraints was positively associated with intensification of maize-based farming systems around Hawassa and increases in oxen ownership (an indicator of farm power) was associated with extensification of wheat-based farming systems around Asella. In Central Luzon, farm and regional factors did not lead to different levels of intensification within the variation of rice farms investigated and the most striking effect was that direct-seeding (and thus slightly lower rice yields) was mostly adopted in larger farms, and used lower amounts of hired labour, compared to transplanting. In the Netherlands, the analysis of rotational effects on crop yields provided inconclusive results but confounding effects with e.g. rented land do not allow to conclude that these are not at stake in this farming system.

This thesis broadens the discussion on yield gaps by moving from the technical aspects underlying their estimation towards the broader farm level opportunities and constraints undermining their closure. Overall, insights from contrasting case studies support conventional wisdom that intensification of agriculture needs to occur in the 'developing South', where yield gaps are large and resource use efficiency low, while a focus on improving sustainability based on sustainable intensification (or even extensification) is more appropriate in the 'developed North', where yield gaps are small and resource use efficiency high.

On the role of soil organic matter for crop production in European arable farming
Hijbeek, Renske - \ 2017
University. Promotor(en): Martin van Ittersum, co-promotor(en): Hein ten Berge. - Wageningen : Wageningen University - ISBN 9789463436632 - 211
soil fertility - soil fertility management - soil management - soil conservation - organic matter - soil organic matter - nitrogen - nitrogen fertilizers - green manures - manures - straw - soil carbon sequestration - cover crops - crop yield - yields - meta-analysis - food security - europe - drivers - barriers - bodemvruchtbaarheid - bodemvruchtbaarheidsbeheer - bodembeheer - bodembescherming - organische stof - organisch bodemmateriaal - stikstof - stikstofmeststoffen - groenbemesters - mest - stro - koolstofvastlegging in de bodem - dekgewassen - gewasopbrengst - opbrengsten - meta-analyse - voedselzekerheid - europa - chauffeurs - barrières

The aim of this thesis was to improve understanding of the role of organic inputs and soil organic matter (SOM) for crop production in contemporary arable farming in Europe. For this purpose, long-term experiments were analysed on the additional yield effect of organic inputs and savings in mineral fertiliser. In addition, a farm survey was conducted to find drivers and barriers for the use of organic inputs and to assess if arable farmers in Europe perceive a deficiency of SOM.

The findings in this thesis suggest that at least on the shorter term, on average, there seems to be no immediate threat from a deficiency of SOM to crop production in arable farming in Europe. The long-term experiments showed that with sufficient use of only mineral fertilisers, on average, similar yields could be attained over multiple years as with the combined use of organic inputs and mineral fertiliser. This was reflected in the farm survey, in which a large majority of farmers indicated not to perceive a deficiency of SOM. Analysis of long-term experiments also showed that more mineral fertiliser N was saved when using farmyard manure at high N rates (with mineral fertiliser application) than at low N rates (without mineral fertiliser application), based on comparisons at equal yield.

Specific crops and environments did benefit from organic inputs and more SOM in terms of crop production. Long-term experiments showed that organic inputs give benefit to crop production in wet climates and on sandy soils. In addition, farmers perceived a higher deficiency of SOM on steep slopes, sandy soils, wet and very dry climates. The additional yield effect of organic inputs was significant for potatoes. More in general, farmers who cultivated larger shares of their land with specialized crops (including potatoes, sugar beets, onions and other vegetables) than cereals perceived a higher deficiency of SOM. It seems that while the functions of SOM can be replaced with technical means to a large extent (e.g. tillage, use of mineral fertilisers), there are limits to this technical potential when environmental conditions are more extreme and crops are more demanding.

The farm survey revealed that farmers perceive a trade-off between improved soil quality on the one hand and increased pressures from weeds, pests and diseases and financial consequences on the other hand when using organic inputs. If policies aim to stimulate the maintenance or increase of SOM, more insight is needed into the conditions that regulate the pressures of weeds, pests and diseases in response to organic inputs. Financial consequences (at least on the short term) should also be accounted for. More importantly however, benefits from SOM for crop production cannot be taken for granted. Only in specific situations such benefits will exist. If European policies on SOM aim to include benefits for crop production, focus should be on areas with more extreme environmental conditions (very dry or wet climates, steep slopes, sandy soils), or cropping systems with more specialized or horticultural crops rather than cereals.

Species mixing effects on forest productivity in the Netherlands
Lu, Huicui - \ 2017
University. Promotor(en): Frits Mohren, co-promotor(en): Frank Sterck. - Wageningen : Wageningen University - ISBN 9789463436397 - 134
mixed forests - temperate zones - deciduous forests - soil fertility - light - yields - netherlands - gemengde bossen - gematigde klimaatzones - loofverliezende bossen - bodemvruchtbaarheid - licht - opbrengsten - nederland

Many monoculture forests (dominated by a single tree species) have been converted to mixed-species forests (dominated by more than one tree species) in Europe over the last decades. The main reason for this conversion was to increase productivity, including timber production, and enhance other ecosystem services, such as conservation of biodiversity and other nature values. In addition, it has been suggested that mixed-species forests are more resistant, resilient and stable to disturbances.

In line with the niche complementarity hypothesis, inter-specific differences in crown architecture, leaf phenology, shade tolerance and root distribution may allow tree species to partition resources in mixed forests. Such mechanisms may lead to a higher productivity of mixed forests versus monoculture forests, a phenomenon often referred to as overyielding. Interestingly, the stress-gradient hypothesis and the resource-ratio hypothesis suggests that such inter-specific interactions vary along a soil fertility gradient, but in different ways. The stress-gradient hypothesis emphasizes that more efficient partitioning increases overyielding at low fertility soils, whereas the resource ratio hypothesis considers that the denser packing of crowns on fertile soils allows for partitioning of light and overyielding on high fertility soils. Several studies have been carried out about species mixing effects on forest productivity, but so far their findings are ambiguous. Probably, this ambiguity comes from the sites that they studied, which differ in species, age, management history, and/or environmental conditions.

This thesis analyses the mixing effect on productivity in relation to the combination of species, stand age and soil fertility, and discusses possible consequences of forest management, for five two-species mixtures in the Netherlands: Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)beech (Fagus sylvatica L.), pine (Pinus sylvestris L.)oak (Quercus robur L.), oakbeech, oakbirch (Betula pendula Roth) and pinebirch. These mixtures and their corresponding monoculture stands were studied using long-term permanent forest plots over multiple decades, but also using two inventories (around 2003 and 2013) across the entire Netherlands. These forest plots data were used together with empirical models at total stand level (chapter 2), species level (chapter 3) and tree level (chapter 4) to evaluate the mixing effect on forest productivity.

In chapter 2, four two-species mixtures and their corresponding monospecific stands were compared for productivity (volume stem wood in m3 ha-1 year-1). It was explored whether mixing species differing in leaf phenology and shade tolerance would lead to overyielding of mixed forest stands, and whether overyielding changes with stand development. In line with the niche complementarity hypothesis, the two evergreen–deciduous species mixtures (Douglas-fir–beech and pine–oak) showed overyielding whereas deciduous–deciduous species mixtures (oakbeech and oakbirch) did not. The overyielding was strongest for the Douglas-fir–beech mixture than the pine–oak mixture, which can be attributed to the greater difference in shade tolerance in the former mixture. Overyielding did not significantly change with stand development. It is argued that the regular thinning maintained the ability of species to partition resources, i.e. the complementary resource use in those mixed stands over all stand ages.

In chapter 3, it was analysed which of the two species in these four mixtures contributed to overyielding, and whether this overyielding changed along a soil fertility gradient. It was discovered that both the fast-growing and the slow-growing species could contribute to overyielding. Yet, it was mainly the fast-growing Douglas-fir that contributed to higher productivity in the Douglas-fir–beech mixtures, and the slow-growing oak that did so in the pine–oak mixtures. For both mixtures, the greatest relative productivity gain was achieved by mixtures on the poorer soils. At first sight, these results seem in line with the stress-gradient hypothesis and not the resource-ratio hypothesis. Yet, it was argued that not only complementary use of soil resources, but also use of light, may contribute to the higher productivity of mixed stands on the poorer soils.

In chapter 4, it was assessed how the growth of individual trees in mixtures was influenced by inter- and intra-specific competition, and whether this competition was mainly size-symmetric for soil resources or size-asymmetric for light on soils differing in fertility. This chapter focussed on three mixtures, i.e. oak–birch, pine–oak and pine–birch, which were available at sufficient numbers in the Dutch national forest inventory data. It was concluded that intra-specific competition was not necessarily stronger than inter-specific competition and this competitive reduction was less seen at lower soil fertility and dependent on species mixtures, which is not in line with the stress-gradient hypothesis. Moreover, size-asymmetric competition for light was more associated with tree basal area growth than size-symmetric competition for soil resources, suggesting that light is the most limiting resource. Competition for light was generally much stronger at high fertility soils, supporting the resource-ratio hypothesis. These results suggest that light is the most limiting resource for tree basal area growth and that reduced competition for light can be explained to some degree by complementarity in light use to increase tree growth in mixed forests.

This thesis thus described the productivity patterns when mixing tree species and explored possible mechanisms of higher productivity in mixed stands compared with monoculture stands in the Netherlands. Complementary use of aboveground and belowground resources probably contributes to the higher productivity in mixed stands, but other factors including pathogens, nutrient cycling and litter decomposition were not addressed but cannot be excluded. Overyielding in Douglas-fir–beech and pine–oak mixtures was maintained over time, probably owing to the intensive thinning in Dutch forests. The results shed new light on the stress-gradient and resource-ratio hypotheses. For mixtures in Dutch forest, the greatest productivity gain in Douglas-fir–beech and pine–oak mixtures was achieved on the poorer soils, and it was argued that this is at least partially driven by complementary use of light, while the role of complementarity in use of soil resources is more obscure. Overall, this thesis suggest a substantial potential of species mixing for increasing productivity, which may run in parallel with enhancing other ecosystem services such as conservation of diversity and other nature values. Yet, more experimental studies on productivity in mixed stands are required to better unravel alternative mechanisms. Such understanding is required to manage the forests effectively in a century of unpreceded human driven changes in environmental conditions.

Mogelijke oorzaken van een dalende opbrengst van witte klaver (Trifolium repens L.) in de tijd
Boer, H.C. de; Eekeren, N. van - \ 2017
Wageningen : Wageningen Livestock Research (Wageningen Livestock Research rapport 1025) - 36
trifolium repens - opbrengsten - reductie - voedingsstoffen - melkveehouderij - yields - reduction - nutrients - dairy farming
Onderzoek naar oorzaken en oplossingen van grasklaverdaling in de landbouw.
Algae production pilot open ponds Lelystad : Results 2013 - 2015
Dijk, W. van; Weide, R.Y. van der; Gennep, Coen van - \ 2016
Lelystad : ACRRES - Wageningen UR (PPO rapport 583) - 63 p.
algae culture - biomass production - aquatic biomass - yields - pilot projects - growout ponds - cropping systems - biobased economy - algenteelt - biomassa productie - aquatische biomassa - opbrengsten - proefprojecten - groeivijvers - teeltsystemen
In 2012 two open microalgae ponds (one indoor and one outdoor, both 250 m2) were built at the ACRRES pilot site in Lelystad. Both ponds are connected to an anaerobic digester and utilise excess heat and flue gas (CO2) from the Combined Heat and Power unit (CHP). In this report the results of the algae production monitoring and the additional experiments are given for the period 2013-2015.
Examining growth, yield and bean quality of Ethiopian coffee trees : towards optimizing resources and tree management
Bote, Adugna - \ 2016
University. Promotor(en): Niels Anten, co-promotor(en): Jan Vos; F.L. Ocho. - Wageningen : Wageningen University - ISBN 9789462578319 - 138
coffea - coffea arabica - trees - growth - yields - quality - radiation - nitrogen - agroecosystems - bomen - groei - opbrengsten - kwaliteit - straling - stikstof - agro-ecosystemen

Coffee (Coffeaarabica L.)bean production and quality are determined by a diversity of interacting factors (e.g. shade, nitrogen, crop traits). Bean yield increases with increase in radiation, but adequate fertilizer suppliesare needed to sustain the productivity. This thesis analysed coffee tree growth, bean production and bean quality in relation to different degrees of exposure to radiation and nitrogen supply. Growth of leaves and branches and properties of leaves such as specific leaf area, nitrogen content per unit leaf area and light-saturated rate of photosynthesis were determined. Radiation interception and nitrogen uptake were also determined as were radiation use efficiency and apparent nitrogen recovery. Tree biomass and coffee bean yield responded positively to both radiation and nitrogen supply. Abundant bean yield to the detriment of vegetative growth, however, resultedin biennial bearing in coffee trees. Effects of fruit load on coffee treegrowth and productivity were studied for two consecutive years and the resultshowed that competition between fruit growth and vegetative growth predisposed the trees for biennial bearing. Reduced vegetative growth when fruit load is high reduces the number of flower bearing nodes and hence yields in the next season. Coffee quality is a sum of favourable characteristics that satisfies requirements of different actors in the coffee chain and is the factor determining the price on the coffee market. This study has also examined coffee quality attributes in relation to radiation and nitrogen, fruit load manipulation, and genotype by environment (different altitudes) interactions. The result indicated that factors and conditions that support non-limiting supply of resources for bean to grow and a sufficient long period of maturation promote coffee bean quality. Overall, the study gained further understanding of coffee tree growth, yield and bean quality responses to aforementioned factors and explored traits that underlie the patterns. Further works are required to use the traits and describe the behaviour of coffee trees in different agro-ecosystems.

Boseigendom in Twente en Salland : resultaten van een enquête onder kleine boseigenaren in Twente en Salland
Clerkx, A.P.P.M. ; Hengeveld, G.M. ; Schelhaas, M. ; Helmink, A.T.F. - \ 2016
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2731) - 57 p.
bossen - bosbezit - bosbedrijfsvoering - biomassa - opbrengsten - salland - twente - forests - forest ownership - forest management - biomass - yields
In de regio Twente/Salland is onderzoek uitgevoerd naar het boseigendom en motivatie van boseigenaren. Alle eigenaren met bosbezit van ten minste 0,5 ha hebben een enquête ontvangen met persoonlijke vragen over de eigenaar, het eigendom, beheer en oogst. Daarnaast is gekeken hoe gevoelig de eigenaren zijn voor verschillende strategieën die gericht zijn op vergroting van de houten biomassaoogst uit hun bos. Met deze antwoorden is voor de regio een indeling in eigenaarsgroepen gemaakt. Voor elke groep is een schatting gemaakt van het effect van de mobilisatiestrategieën en de hoeveelheid extra te mobiliseren hout.
Grasgroei meten met de grashoogtemeter
Holshof, G. ; Stienezen, M.W.J. - \ 2016
Wageningen : Wageningen UR Livestock Research (Livestock Research rapport 925) - 23 p.
grassen - groei - meting - opbrengsten - graslandbeheer - grasses - growth - measurement - yields - grassland management
De waarde van een gedetailleerde bodemkaart van een waterwingebied
Knotters, M. - \ 2015
Stromingen : vakblad voor hydrologen 21 (2015)2. - ISSN 1382-6069 - p. 29 - 41.
water catchment - groundwater level - yields - damage - soil surveys - soil types - calculation - estimates - noord-brabant - waterwinning - grondwaterstand - opbrengsten - schade - bodemkarteringen - bodemtypen - berekening - schattingen
Boeren in waterwingebieden hebben recht op vergoeding van schade veroorzaakt door daling van de grondwaterstand als gevolg van waterwinning. Bij de berekening van de schades wordt onder meer gebruik gemaakt van bodemkaarten. De vraag die in dit artikel centraal staat is of gedetailleerde kaarten (schaal 1:25.000) opweegt tegen de baten, of dta met toepassing van de landelijke bodemkaart (schaal 1: 50.000) kan worden volstaan. Een validatiestudie is verricht voor het gebied Vierlingsbeek.
Opbrengsten en kosten in de kottersector : product van Kenniskringen visserij
Turenhout, M.N.J. ; Klok, A.J. ; Zaalmink, W. - \ 2015
visserij - vissersschepen - economische analyse - kosten - opbrengsten - duurzaamheid (sustainability) - fisheries - fishing vessels - economic analysis - costs - yields - sustainability
Als kottereigenaar is het van belang om economisch duurzaam te ondernemen. De kosten mogen gemiddeld niet hoger liggen dan de verkregen opbrengsten. Maar waar bestaan de kosten en opbrengsten in de kottersector daadwerkelijk uit? In deze factsheet van Kenniskringen Visserij wordt een overzicht gegeven van de belangrijkste kosten en opbrengsten.
Strain improvement of oleaginous microalgae
Jaeger, L. de - \ 2015
University. Promotor(en): Gerrit Eggink; Rene Wijffels, co-promotor(en): Dirk Martens. - Wageningen : Wageningen University - ISBN 9789462574847 - 200
algen - biomassa - oliën - productiviteit - opbrengsten - transcriptomica - triacylglycerol lipase - bioreactoren - transformatie - mutanten - algenteelt - biomassa productie - algae - biomass - oils - productivity - yields - transcriptomics - bioreactors - transformation - mutants - algae culture - biomass production

The increasing world population and living standards have enlarged the demand for food, feed, and for chemicals. Traditional fossil fuel based commodities need to be replaced, not only because these resources are finite, but also to relieve the impact of carbon emission and pollution, resulting from fossil fuel derived processes. Much attention is on using plants to produce sustainable, renewable alternatives to petrochemical based processes. Palm oil is the crop with the highest lipid yield known today, but the production of palm oil causes deforestation on a large scale. Microalgae are a promising platform for the production of sustainable commodity products. A commodity product that can be produced in microalgae is triacylglycerol (TAG). The TAG molecules that are accumulated in microalgae are comparable to the TAG profiles of commonly used vegetable oils, and can directly be applied for edible oil as well as for biodiesel production. Currently, microalgae derived products have proven to be functional and a potential replacement for conventional crops. However, microalgae derived products, especially TAGs, are not economically feasible yet. In order to make microalgal derived products a reality we need to decrease the production costs by smart technological solutions, biological understanding and metabolic engineering.

To get more insight in the lipid accumulation mechanism of microalgae, and to define targets for future strain improvement strategies, transcriptome sequencing of the oleaginous microalgae Neochloris oleoabundans was done. This oleaginous microalga can be cultivated in fresh water as well as salt water. The possibility to use salt water gives opportunities for reducing production costs and fresh water footprint for large scale cultivation.

In chapter 2 the lipid accumulation pathway was studied to gain insight in the gene regulation 24 hours after nitrogen was depleted. Oil accumulation is increased under nitrogen depleted conditions in a comparable way in both fresh and salt water. The transcriptome sequencing revealed a number of genes, such as glycerol-3-phosphate acyltransferase and via glycerol-3-phosphate dehydrogenase, that are of special interest and can be targeted to increase TAG accumulation in microalgae. NMR spectroscopy revealed an increase in proline content in saline adapted cells, which was supported by up regulation of the genes involved in proline biosynthesis. In addition to proline, the ascorbate-glutathione cycle seems to be of importance for successful osmoregulation by removal of reactive oxygen species in N. oleoabundans, because multiple genes in this pathway were upregulated under salt conditions. The mechanism behind the biosynthesis of compatible osmolytes in N. oleoabundans can be used to improve salt resistance in other industrially relevant microalgal strains.

Another very promising candidate for TAG production is the oleaginous green microalga Scenedesmus obliquus.

In chapter 3, UV mutagenesis was used to create starchless mutants, since no transformation approach was available for this species, due to its rigid and robust cell wall. All five starchless mutants that were isolated from over 3500 screened mutants, showed an increased triacylglycerol productivity. All five starchless mutants showed a decreased or completely absent starch content. In parallel, an increased TAG accumulation rate was observed for the starchless mutants and no substantial decrease in biomass productivity was perceived. The most promising mutant (Slm1) showed an increase in TFA productivity of 41% at 4 days after nitrogen depletion and reached a TAG content of 49.4% (%CDW).

In chapter 4 the Slm1 strain was compared to the wild type strain using photobioreactors. In the wild type, TAG and starch accumulated simultaneously during initial nitrogen starvation, and starch was subsequently degraded and likely converted into TAG. The Slm1 did not produce starch and the carbon and energy acquired from photosynthesis was partitioned towards TAG synthesis. This resulted in an increase of the maximum TAG content in Slm1 to 57% (%CDW) compared to 45% (%CDW) in the wild type. Furthermore, it increased the maximum yield of TAG on light by 51%, from 0.144 in the wild type to 0.217 g TAG mol-1 photon-1 in the Slm1 mutant. No differences in photosynthetic efficiency between the Slm1 mutant and the wild type were observed, indicating that the mutation specifically improved carbon partitioning towards TAG and the photosynthetic capacity was not affected.

To identify the mutation that caused the starchless phenotype of Slm1 the transcriptome of both the wild type and the Slm1 mutant was sequenced as described in chapter 5. A single nucleotide polymorphism (SNP) was discovered in the small subunit of the starch biosynthesis rate-controlling enzyme ADP-glucose pyrophosphorylase, which resulted in the introduction of a STOP codon in the messenger RNA of the enzyme. The characterization of the mutation increases the understanding of carbon partitioning in oleaginous microalgae, leading to a promising target for future genetic engineering approaches to increase TAG accumulation in microalgae.

To use the insight that is gained in chapters 2-5 for metabolic engineering of TAG accumulation and carbon partitioning, a metabolic engineering toolbox is required. However, the development of transformation protocols for new and less well studied industrially relevant microalgae is challenging. In chapter 6, a simple and effective tool for the optimization of transformation protocols is proposed. Optimal voltage settings were determined for five microalgae: C. reinhardtii, Chlorella vulgaris, N. oleoabundans, S. obliquus, and Nannochloropsis sp. This method can be used to speed up the screening process for species that are susceptible for transformation and to successfully develop transformation strategies for industrially relevant microalgae, which lack an efficient transformation protocol.

In addition to the increase in productivity, improving the quality in terms of fatty acid composition of TAG molecules would be desired as well. For example, the accumulation of stearic acid rich TAG molecules is of special interest, because of the improved structural properties. The lipid accumulating starchless mutant of the model species C. reinhardtii BAFJ5 was used as model species in chapter 7, since genetic toolbox is well established for this species. In this chapter, stearoyl-ACP desaturase (SAD), is silenced by artificial microRNA. The mRNA levels for SAD were reduced after the silencing construct was induced. In one of the strains, the reduction in SAD mRNA resulted in a doubling of the stearic acid content in triacylglycerol molecules, which shows that increasing the fraction of stearic acid in TAG is possible. Furthermore, we hypothesize that in addition to direct conversion in the chloroplast, C. reinhardtii is able to redirect stearic acid from the chloroplast to the cytosol and convert it to oleic acid in the endoplasmic reticulum by stearoyl-CoA desaturase.

In chapter 8, an outlook is given on microalgal strain improvement strategies for the future, reflecting on the results obtained in this thesis. Also a roadmap is suggested to get genetically modified microalgal derived products on the market. The results presented in this thesis, provide a significant improvement in the understanding of TAG accumulation and carbon partitioning in oleaginous microalgae. Furthermore, improved microalgal strains with increased TAG accumulation or improved TAG fatty acid composition under nitrogen depleted conditions were generated. In addition, an outlook is presented in which the major bottlenecks are presented in future industrial applications of microalgae.

The economic value of detailed soil survey in a drinking water collection area in the Netherlands
Knotters, M. ; Vroon, H.R.J. - \ 2015
Geoderma Regional 5 (2015). - ISSN 2352-0094 - p. 44 - 53.
bodemkarteringen - grondwaterstand - waterwinning - opbrengsten - berekening - veldwerk - midden-limburg - soil surveys - groundwater level - water catchment - yields - calculation - field work
In large parts of the Netherlands crop growth depends on the water table. If groundwater is withdrawn the water table is lowered and agricultural crop production may be reduced. Farmers in drinking water collection areas are legally compensated for these crop yield reductions. Soil maps are used to estimate crop yield reductions and hence legal compensations. We calculated the benefit of a detailed soil survey from the reduction of errors in legal compensations that can be achieved if a detailed soil map, 1:25,000, is used for estimation instead of the national soil map, 1:50,000. We compared this error reduction with the costs of the detailed soil survey. We selected 40 farms by stratified random sampling in the drinking water collection area ‘Vierlingsbeek’. At each farm soil profile descriptions were made at a total of 137 randomly selected locations. Legal compensations estimated from the 1:50,000 soil map and information from the 1:25,000 soil map were compared with legal compensations calculated from the soil profile descriptions, and errors were calculated for each farm in € ha- 1 year- 1. With an investment in detailed soil survey of €30 ha- 1 the absolute error could be reduced on average by €13.16 ha- 1 year- 1, the present value of which is €258 ha- 1 assuming an interest of 3% and yearly compensations during a period of 30 years. We conclude therefore that for this study area detailed soil survey was worth the costs. Furthermore, we conclude that insight in the spatial dependence structure of classification errors at soil maps of various scales would be very helpful prior information in deciding on the detail of soil survey needed to support decisions at farm level.
NSO-typering 2015; Typering van agrarische bedrijven in Nederland
Everdingen, W.H. van - \ 2015
Den Haag : LEI Wageningen UR (Nota / LEI 2015-084) - 36
landbouw bedrijven - bedrijven - bedrijfsvergelijking in de landbouw - bedrijfsvoering - opbrengsten - inkomsten uit het landbouwbedrijf - bedrijfsgrootte in de landbouw - bedrijfsgegevens - standaardisering - classificatie - agrarische economie - farming - businesses - farm comparisons - management - yields - farm income - farm size - farm accountancy data - standardization - classification - agricultural economics
In 2014 is voor de Nederlandse variant een nieuw kengetal geïntroduceerd: de Standaard Verdiencapaciteit (SVC) van bedrijven. Dat kengetal is ontwikkeld vanwege verschillen in marge tussen de sectoren. Met de SVC is de bedrijfsgrootte van bedrijven over bedrijfstypen heen meer gerelateerd aan arbeidsinzet en resultaat dan bij de Standaardopbrengst (SO) het geval is. De classificatie is gekoppeld aan de Landbouwtelling. De normen worden berekend voor de categorieën dieren en gewassen die in de Landbouwtelling worden uitgevraagd. Het doel van dit document is inzicht verschaffen in de achtergronden, rekenschema’s, indelingen en normen die bij de typering in gebruik zijn rond de Landbouwtelling van 2015. Achtereenvolgens komen in de volgende paragrafen de Standaardopbrengst (1), de NSO-typering (2), de Standaard Verdiencapaciteit (3) en het gebruik van de gegevens (4) aan bod.
Goede snijmaïs telen bij lagere bemestingsnormen
Curth-van Middelkoop, J.C. - \ 2015
zea mays - bemesting - ontwerpberekeningen - organische meststoffen - opbrengsten - fertilizer application - design calculations - organic fertilizers - yields
De flyer geeft advies over het telen van snijmais binnen de strenger geworden gebruiksnormen. Gekeken wordt naar de opbrengsten en het principe van organische mest in de rij.
Handleiding betere mestbenutting
Bussink, D.W. - \ 2015
bemesting - weiden - zea mays - mestgiften - bekalking - voedingsstoffen - dierlijke meststoffen - kunstmeststoffen - opbrengsten - voederkwaliteit - fertilizer application - pastures - dressings - liming - nutrients - animal manures - fertilizers - yields - forage quality
Voor de groei van gras en mais is de juiste (kunst)mestsoort van belang voor een goede groei en ontwikkeling. Deze handleiding gaat hierop in en sluit tevens aan bij de leidraad 'Benut N-meststoffen optimaal, te beginnen in het voorjaar’.
Waardekaarten Ridens & Recifs
Machiels, M.A.M. - \ 2015
IJmuiden : IMARES (Rapport / IMARES Wageningen UR C073/15) - 18
kaarten (charts) - kaarten - frankrijk - kustwateren - vergelijkend onderzoek - opbrengsten - visvangsten - schol - scophthalmus rhombus - tarbot - charts - maps - france - coastal water - comparative research - yields - fish catches - plaice - turbot
In dit rapport beantwoorden wordt een offerteaanvraag van de Nederlandse Vissersbond van 18 februari 2015 beantwoord waarin zij vroegen om waardekaarten en tabellen van de N2000 gebieden Ridens & Récifs voor de Franse kust.
Nieuwsbrief Basis juli 2014
Balen, D.J.M. van; Haagsma, W.K. - \ 2014
PPO AGV
akkerbouw - bodemfactoren - proeven op proefstations - grondbewerking - biologische landbouw - organische stof - opbrengsten - arable farming - edaphic factors - station tests - tillage - organic farming - organic matter - yields
Nieuwsbrief in het kader van de bodemprojecten op PPO-proefbedrijf Lelystad.
AGRICOM 2.01 : theorie en gebruikershandleiding
Mulder, H.M. ; Veldhuizen, A.A. - \ 2014
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2576) - 61
bodemwater - grondwaterstand - ecohydrologie - opbrengsten - kosten-batenanalyse - landbouw - waterbeheer - modellen - soil water - groundwater level - ecohydrology - yields - cost benefit analysis - agriculture - water management - models
AGRICOM is een acronym voor AGRIcultural COst Model. AGRICOM is een agro-economisch model dat op basis van de resultaten van een hydrologisch model kosten en baten voor de landbouwsector in Nederland berekent. Dit betreft de effecten van te droge, te natte of te zoute omstandigheden op de Nederlandse landbouw. De kosten en baten analyse wordt per jaar of over een langjarig gemiddelde periode uitgevoerd. Het AGRICOM model dient ter ondersteuning bij beleidsvragen als: wat zijn kansrijke maatregelen om landbouwschade te voorkomen, wat zijn de neveneffecten voor de landbouw van anti-verdrogingsmaatregelen in natuurgebieden en hoe efficiënt is beregening.
Nieuwe maisrassen voor hogere opbrengst
Groten, J.A.M. - \ 2014
Boerderij 100 (2014)12. - ISSN 0006-5617 - p. R32 - R34.
maïs - rassen (planten) - rassenlijsten - opbrengsten - rassenproeven - voedergewassen - rundveehouderij - maize - varieties - descriptive list of varieties - yields - variety trials - fodder crops - cattle husbandry
CSAR en DLV Plant publiceren rassenlijsten met nieuwe maisrassen. Uit beide lijsten blijkt dat kwekers de nadruk leggen op hoge opbrengsten.
Walnoten in de uitloop
Bestman, M. ; Oosterbaan, A. - \ 2014
De Pluimveehouderij 44 (2014). - ISSN 0166-8250 - p. 26 - 27.
dierenwelzijn - uitloop - pluimveehouderij - beplantingen - walnoten - bomen - opbrengsten - pluimvee - dierlijke productie - huisvesting, dieren - animal welfare - outdoor run - poultry farming - plantations - walnuts - trees - yields - poultry - animal production - animal housing
Bomen voor Buitenkippen is op excursie geweest naar enkele beplantingen waar al veel ervaring is opgedaan met walnotenbomen.
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