NJAS: wageningen journal of life sciences

Published by Elsevier
Print ISSN: 1573-5214
Measurements of N2 fixation by Arachis hypogaea grown on an Ultisol (Grossarenic Kandiudult) in North Lampung, Sumatra were obtained by i) the 15N dilution method by applying a small dose of 15N in solution mixed with a carbon source and ii) by the 15N natural abundance method (δ15N). For both methods non-nodulating groundnuts and maize were used as reference plants. While the 15N dilution method led to a large spatial variation (both in depth and time) in plant available 15N, spatial variations of the natural 15N abundance with soil depth (6–9 %o), time (9–12 %o over one year) and space were comparatively small. The δ15N of the mineralizable N pool was greater than that of the total soil N which was reflected in high δ15N values of the reference plants.
A new, flexible curve-fit model for linear to concave rank abundance curves was conceptualized and validated using observational data. The model links the geometric-series model and log-series model and can also fit deeply concave rank abundance curves. The model is based — in an unconventional way — on the negative-binomial distribution and calculates (like the log-series model) a species-diversity index. The index is defined as the expected number of singleton species (species present with one individual) in an infinitely large sample. The new model could satisfy the need for more flexible curve-fit models with which differences and changes in the shape of the rank abundance curve can be more accurately investigated. The common rank abundance curve-fit models are lacking that flexibility.
Calculating a single-sample rank abundance curve by using the negative-binomial distribution provides a way to investigate the variability within rank abundance replicate samples and yields a measure of the degree of heterogeneity of the sampled community. The calculation of the single-sample rank abundance curve is used in combination with the negative-binomial rank abundance curve-fit model to analyse the principal effect of clustering on the species-individual (S-N) curve and the species-area curve. With the usual plotting of S against log N or log area, assuming that N is proportional to area, S-N curves and species-area curves are the same curves with only a shifted horizontal axis. Clustering results in a lower recorded number of species in a sample and stretches the S-N curve and species-area curve over the horizontal axis to the right. In contrast to what is suggested in the literature, we surmise that the effect of clustering on both curves will gradually fade away with increasing sample size. Since the slopes of the curves are not constant, they cannot be used as species diversity indices or site discriminant. S-N curves and species-area curves cannot be extrapolated.
This paper examines the gathering of wild orchids and its effect on orchid species diversity and abundance in rural communities with high prevalence of HIV/AIDS and high numbers of orphans. The study was conducted in three villages in the Makete District of Tanzania. The study used a triangulation of ethno-botanical, anthropological and sociological methodologies. On the three gathering sites, we found a total of 12 different orchid species (7 edible and 5 non-edible ones) confirmed by an expert botanist, although local gatherers identified many more species. The Shannon-Wiener diversity index significantly differed among the three gathering sites. Analyses of focus group discussions and household surveys revealed that HIV/AIDS orphans and non-orphan children were the main gatherers of wild orchids. HIV/AIDS orphans (n = 55) gathered significantly more frequently (4.1 ± 1.8 times per week) than non-orphan children (n = 49; 1.9 ± 1.3 times per week) (P < 0.01). There was a statistically significant interaction between village and type of gatherer (P < 0.05). Scattered observations of changes in orchid species abundance over time were done using gatherers' indigenous knowledge and opinions. Orchid abundance peaked during May 2006. The study showed increasing abundance of non-edible orchid species and decreasing abundance of edible ones. There were highly significant, linear negative relationships between gathering pressure on the one hand and total number of orchid plants, total number of orchid species, number of edible orchid plants and number of edible orchid species on the other. These relationships were not statistically significant for non-edible orchids. We surmise that gathering edible orchid tubers is likely to become unsustainable, because once its tuber is harvested the plant does not recover or survive.
The impact of clustering on rank abundance, species-individual (S-N) and species-area curves was investigated using a computer programme for in silico sampling. In a rank abundance curve the abundances of species are plotted on log-scale against species sequence. In an S-N curve the number of species (S) is plotted against the log of the total number of individuals (N) in the sample, in a species-area curve S is plotted against log-area. The results from in silico sampling confirm the general shape of S-N and species-area curves for communities with clustering, i.e., a curve that starts with a smaller slope but that later is temporarily steeper than the curve expected for Poisson-distributed species. Extrapolation of S-N and species-area curves could therefore be misleading. The output furthermore shows that sigmoid rank abundance curves (curves of the type of a log-normal or broken stick) can be an artefact of the standard procedure of first sorting the species in sequence of abundance in combination with clustering in the low abundant and rare species. This makes the usual explanation given to the log-normal rank abundance curve dubious. An extension of the negative-binomial rank abundance curve-fit model is discussed to make it suitable for also fitting sigmoid rank abundance curves.
Scientific co-operation between the Chinese Academy of Agricultural Sciences (CAAS) and Wageningen University (WU) has been underway since 1990, especially in the field of plant sciences. In 2001, CAAS and WU initiated a formal joint PhD training programme to further structure their co-operation. The goals of this co-operation are to: (1) initiate long-term institutional collaboration through capacity building; (2) jointly establish a modern laboratory; (3) jointly develop a cross-cultural scientific culture, and (4) set up collaboration in specific fields. Proper selection of PhD research themes was very important in the starting phase, since it would be a basis for good future collaboration. Both the culture and the educational system in the Netherlands and China are very different and this is reflected in their respective PhD educational systems. This article describes the joint PhD programme against the background of these different cultural settings and the different mandates for research of both WU and CAAS. It provides an overview of the requirements and discusses ways to develop a successful co-operation between WU and CAAS.
Reduction of N losses, especially nitrate leaching, is an important objective for dairy farms in the Netherlands. So far, many strategies have focused on changes in strategic and tactical management. Little attention has been paid to operational grassland management. So a conceptual model of operational grassland management was defined, with strong interactions between N rates, realized dry matter (DM) yields, herbage N content, growing days and utilization per cut. Analysis of data from ‘De Marke’ and from monitoring projects shows that grassland production and utilization can be improved by changes in operational grassland management. DM yields for grazing and cutting need to be increased, grazing per paddock must be shorter and slurry must be applied as early as possible. This improved grassland management is able to partly compensate the decrease in DM production resulting from a lower N input.
This paper presents a new methodology for measuring the adoption of sustainable agricultural practices that attempts to integrate positive features of earlier approaches. It measures the degree of sustainability observed by the farmer and, at the same time, is straightforward and efficient in field-by-field appraisals. The methodology proposed starts with the identification of all available soil conservation practices in the area. The practices are then grouped into activity categories and are ranked within each category on the basis of their expected soil conservation effect on the plot system. The resulting ranking system is applied to each plot included in the analysis. Non-linear principal component analysis is carried out on the plot rankings to extract a limited number of major metric components.The method is applied to the Cabuyal watershed in Colombia. The analysis shows that soil management strategies of Cabuyal farmers consist of different combinations of basic soil conservation practices: soil disturbance control, soil protection practices and run-off control. A cluster analysis of the plot scores on these three combinations revealed that the different strategies of soil management are related to the institutional, economic, physical and personal-social factors affecting farms and farmers. The results from the cluster analysis show the usefulness of the proposed methodology for policy purposes.
The quality of grass in terms of form and relative amounts of energy and protein affects both animal production per unit of intake and nitrogen (N) utilization. Quality can be manipulated by herbage management and choice of cultivar. The effects of N application rate (0, 90 or 390 kg N ha−1 year−1), duration of regrowth period (2–3, 4–5, or 6–7 weeks), and cutting height (8 or 12 cm) on the mass fractions of nitrogen (N), water-soluble carbohydrates (WSC), neutral detergent fibre (NDF), acid detergent fibre (ADF), lignin and ash in lamina and sheath material of a high-sugar (Aberdart) and a low-sugar (Respect) perennial ryegrass (Lolium perenne) cultivar, were studied in a factorial field experiment during four seasons in 2002 and 2003. Expressing NDF and ADF mass fractions in g per kg WSC-free dry matter (DM) increased the consistency of treatment effects. The high-sugar cultivar had generally higher WSC mass fractions than the low-sugar cultivar, especially during the late season. Moreover, the relative difference in WSC mass fraction between the two cultivars tended to be higher for the lamina material than for the sheath material, which suggests that the high-sugar trait may be more important under grazing conditions, when lamina forms the bulk of the intake, than under mowing regimes. Longer regrowth periods and lower N application rates increased WSC mass fractions and decreased N mass fractions; interactions between regrowth period and N application rate were highly significant. The mass fractions of NDF and ADF were much less influenced. The NDF mass fraction in terms of g per kg WSC-free DM tended to be higher at lower N application rates and at longer regrowth periods. The effect of cutting height on herbage chemical composition was unclear. In conclusion, high-sugar cultivars, N application rate and length of the regrowth period are important tools for manipulating herbage quality.
To assess (after)effects of temperature on plant development, in vitro potato plantlets produced at 17 or 23 °C (normalisation phase, 3 weeks) were planted into soil in growth chambers at 18/12 or 26/20°C (transplant production phase, 2 weeks), and transplanted to glasshouses at 18/12 or 26/20°C (tuber production phase, 6 weeks). The latter phase commonly takes place in the field. Transition from one phase to another, especially from in vitro to in vivo conditions, greatly increased leaf growth and to a smaller extent stem growth. Within a phase, higher temperature stimulated vegetative growth, but delayed tuber formation and reduced tuber yields, harvest index (HI) and tuber dry matter concentration. Temperature during tuber production was more important for high yield than temperatures during earlier phases. Normalisation and transplant production temperatures nevertheless showed after-effects in later phases. Lower normalisation temperatures advanced plant development: they increased vegetative growth in subsequent phases and finally increased fresh tuber yield and HI. This could have yield advantages at locations where field production seasons are short. Lower transplant production temperatures reduced vegetative growth in the next phase, but enhanced early tuber production. Finally they increased tuber dry weight and HI when tuber production temperatures were high. This may increase yield at locations where field conditions delay tuber formation.
In a world that is developing fast, Africa's relative stagnation is a human tragedy that challenges the development profession. Although climate and geography, and their effect on local institutions, are not in Africa's favour, inappropriate policies (including neglect of agriculture) and weak institutions figure more prominently in the explanation of slow growth. Recent evidence, however, points to accelerated growth in many parts of Africa. Analysis of agriculture shows that adverse effects of nature can be handled effectively, that efforts to develop and apply technologies for intensification in a variety of farming systems are under way, but that sustained adoption by the mass of smallholders has not sufficiently taken place. For that to happen, a variety of time- and location-specific complementary actions — both public and private — are needed, based on a right mix of disciplinary knowledge. With positive changes in governance and a revival of agricultural priorities in Africa, favourable conditions are emerging for renewed and better targeted external aid to support agricultural development.
Using an HIV/AIDS lens in looking at developments in rural livelihoods and agricultural practice reveals a diversity of critical impacts of the epidemic. Still, in most of the countries hardest-hit by HIV/ AIDS the agricultural sector lacks adequate policies and programmes to deal with the crisis. This paper examines the results of research about HIV/AIDS impacts on rural livelihoods and agricultural practice in Sub-Saharan Africa that was carried out during the past five years. Most of the researchers concerned are affiliated with Wageningen University. A number of them contributed as authors to the present special issue. In the review and synthesis presented in this paper both an etic and an emic perspective are used. The etic picture is one of mixed evidence regarding the livelihood effects of HIV/AIDS. Eliciting the views of people living with HIV/AIDS (the emic perspective] revealed continuity between notions of health of the human body and health of crops and the natural environment. This is particularly relevant for the practice and language of extension services and the effectiveness of approaches used by organizations — governmental and non-governmental — that try to mitigate the impacts the epidemic has on farmers and rural livelihoods.
About 2 billion people, mainly women and young children, suffer from iron deficiency. The supply of iron (Fe) falls short when consumed foods have a low Fe content or when absorption of Fe is inhibited by the presence of phytic acid and polyphenols in the diet. Current interventions are dietary diversification, supplementation, fortification and biofortification. In West Africa these interventions have only moderate chances of success due to low purchasing power of households, lack of elementary logistics, lack of central processing of food and the high heterogeneity in production and consumption conditions. A staple food chain approach, integrating parts of current interventions was proposed as an alternative. The research was carried out in several villages in Benin and Burkina Faso to take ecological, cultural and socio-economic diversity into account. The interdisciplinary approach aimed at elaborating interventions in soil fertility management, improvement and choice of sorghum varieties and food processing, to increase Fe and decrease the phytic acid-Fe molar ratio in sorghum-based foods. The phytic acid-Fe molar ratio was used as a proxy for Fe bioavailability in food. Synergy and trade-offs resulting from the integrated approach showed its added value. P fertilization and soil organic amendments applied to increase yield were found to also increase phytic acid content of the grain and thus to decrease its nutritional value. Amounts of Fe and phytic acid and their ratio in the grain differed among sorghum varieties, illustrating the presence of genetic variation for Fe bioavailability. The current local food preparation method for one of the main sorghum-based foods (dibou) in northern Benin did not include processing steps that remove or de-activate anti-nutritional factors reducing Fe bioavailability. The preliminary results suggest that a feasible chain solution consists of breeding for high Fe and moderate phytic acid contents and using soil organic amendments and P fertilization to increase yields but that this needs to be followed by improved food processing to remove phytic acid. Further research on timing of application of phosphate, Fe fertilizer and soil organic amendments is needed to improve phytic acid-Fe molar ratios in the grain. Research on the exact distribution of Fe, phosphate, phytic acid and tannins within the sorghum grain is needed to enable the development of more effective combinations of food processing methods aiming for more favourable phytic acid-Fe molar ratios in sorghum-based food.
This article discusses the impacts of HIV/AIDS on agriculture in Sub-Saharan Africa and the actual and potential role of the agricultural sector in the fight against this disease. It is argued that the agricultural sector has an important role to play in reducing the spread and impacts of HIV/AIDS, in particular in the areas of poverty reduction, ensuring food and nutrition security, enhancing the use of antiretroviral drugs, and advancing gender equality. The failure of the agricultural sector to respond actively to HIV/ AIDS is attributed to a lack of capacity and political will as well as to a lack of empirical data to guide agricultural policy-makers.
Millipedes can cause considerable damage in the production of sweet potato and some other crops in East Africa. Quantitative information on intake of crop diets by and body weight gain of millipedes was collected in short-term no-choice feeding activity laboratory experiments conducted in north-eastern Uganda using female millipedes of the species Omopyge sudanica. Diets consisted of sweet potato and cassava storage root material, groundnut seeds, or maize grains. Differences in intake and body weight gain between diets were not statistically different. The consumption index, i.e., the ratio between intake and body weight gain, was significantly higher for sweet potato than for most other diets. The efficiency of conversion of ingested food, i.e., 100 × the ratio between body weight gain and intake, was significantly lower for the root crops — especially sweet potato — than for the grain crops. The research showed how difficult it is to obtain reliable, quantitative data on the feeding habits of millipedes, but also illustrated that O. sudanica can cause harm to crops in north-eastern Uganda and elsewhere in East Africa.
Assessing potential uptake of agri-environmental schemes based on farm and farmer characteristics only results in an incomplete analysis because it neglects the effects of motivational issues of the institutional design of contracts, as set up by the government, and of social capital. In this paper we describe contract choice using a trivariate probit model and taking into account farm and farmer characteristics and motivational issues. Motivational issues in this study include the perception of institutional design, the use of extension services, trust in the government, and preferences for stable policies. Results show that besides farm and farmer characteristics these factors are important for the likelihood of enrolling in agri-environmental contracts. They do not influence every contract type in the same way and further decisions to conclude different contract types are connected. If farmers perceive the design of an agri-environmental scheme as weak or favour a stable policy they are less likely to conclude contracts for biodiversity protection. Farmers who do not trust the government are less likely to conclude contracts for less intensive practices. Involvement in general networks increases the probability of contracting for wildlife and landscape management and less intensive practices whereas this factor is not important for biodiversity protection. The results suggest that taking into account motivational issues and differentiating towards different contract types can increase effectiveness and efficiency of agri-environmental schemes.
Agri-environmental assessments at the regional scale are restricted by the amount and quality of input data. Such data may be available in public databases. In this study we estimated the extractable soil-P (ESP) in the Sud Milano Agricultural Park in northern Italy. Information about agricultural activities was integrated with ESP values across the area, using a large database of measured soil properties and crop management data collected from individual farms. Four interpolation methods were tested: two forms of ordinary kriging, kriging with external drift and a hybrid form (section-specific mosaic kriging). After splitting the dataset into three sub-sets, ESP was assessed at unsampled farms. High ESP levels were found in maize fields and on animal farms due to large amounts of P fertilizers applied in maize, particularly on animal farms. Using a reference threshold of 20 mg P per kg soil, most of the soils in the area were classified as being rich in ESP. As a result, it was concluded that P fertilization could be suspended in many cases for several years without crop yield decrease. Mosaic kriging showed a lower standard deviation of the prediction error and less smoothing and thus provided a better representation of the actual spatial variation.
Eight researchers from Ghana and Benin, with different backgrounds but all co-operating within the Convergence of Sciences project, conducted diagnostic studies as a first step of their research aimed at developing technologies together with resource-poor farmers. The purpose of including diagnostic studies was to increase the likelihood that the resulting technologies would be grounded in the needs and opportunities of these farmers. To better understand the potential of diagnostic studies for improving the contribution of agricultural research to farmers' livelihoods, a comparative study was conducted of the diagnostic studies carried out by the eight researchers. This research on agricultural research was participatory in that its results were arrived at in consultation with the eight researchers. The comparison revealed that diagnostic studies identified and established forums of stakeholders, especially of farmers, who were to play key roles in the co-construction of knowledge during the field experimental phase that followed the diagnostic studies. The diagnostic studies gave farmers a say in the design and conduct of the experimental phase which allowed them to influence the research process in the direction of developing and testing technologies that work in their circumstances and that satisfy their needs and priorities. In addition, the diagnostic studies have led to transparent choices with respect to the selection of sites, farmers and experiments. Furthermore, the conditions for negotiation were created. Finally, the diagnostic studies played a crucial role in making the partners within the Convergence of Sciences project aware of the importance of contextual framework conditions in determining the relevance of the project.
The poultry sector in the Netherlands is confronted with the EU ban on conventional cages, the public debate on the welfare of hens in furnished cages, the limited perspectives of currently used more welfare-friendly single- or multi-tiered systems (either indoor or outdoor), and with questions about the natural behaviour of animals and the robustness of current production systems. To arrive at new and sustainable husbandry systems for laying hens a new design approach was developed and applied. The work-scheme of the approach consisted of four phases: (1) collecting information and network building, (2) a thorough analysis of problems followed by making strategic choices, (3) developing a structured design, and (4) reporting and communication. The approach incorporated interdisciplinary and multi-stakeholder interactive methods, integrating scientific and tacit knowledge. The main results of the study were (1) a Brief of Requirements for the laying hen, the farmer and the citizen/consumer as key players in a sustainable development, and (2) two new attractive and feasible husbandry concepts for future egg production. The approach succeeded in identifying the underlying needs and requirements of actors, bridging the gap between seemingly conflicting requirements and stimulating new initiatives towards sustainable development.
Weeds are an emerging constraint on crop production, as a result of population pressure and more intensive use of cultivated land. A diagnostic study was carried out from June through August 2002 in the five agro-ecological zones of Benin (1) to identify the relative importance of weeds among major production constraints, (2) to better understand farmers' perceptions of weed problems, and (3) to take cognizance of their reactions and the different actors involved in weed management technology development. The study also aimed at suggesting the development of weed management strategies that work and are acceptable under small-scale farmers' conditions. Data were collected through semi-structured and unstructured group and/or individual interviews, and through participant observation, transect studies and weed identification during field visits. The results show considerable diversity in biophysical constraints and socio-economic conditions. Population density has led to high pressure on arable land, resulting in land degradation and weed problems. In all situations, pernicious (Imperata cylindrica, Cyperus spp., Commelina spp.) and parasitic (Striga spp.) weeds are difficult to eradicate, causing substantial food crop yield losses and threatening the livelihood of people. Land and labour shortage, low commodity prices and lack of credit were the main constraints hindering weed management. Causes, effects and consequences were analysed, taking into account the socio-economic context. The study's findings with respect to weed management measures, and their adaptation and constraints in using them, suggest that effective and acceptable weed management strategies should be developed, taking into account both biological and social science perspectives with a focus on adding value to indigenous knowledge.Promising strategies for discovery learning about weed management were identified, in order to foster sustainable crop production in Benin.
This paper focuses on ethno-cognitive connections between HIV/AIDS and banana plants in the Bahaya agricultural society that emerged from an anthropological study carried out in 2005–2006 in Nsisha, a rural village in Bukoba District, north-western Tanzania. The paper briefly describes the historical context of HIV/AIDS and how its onset coincided with a decline in the production of bananas, the historical, cultural and staple food of the Bahaya people. In addition, references are made in Luhaya, the primary language spoken in the region, to demonstrate that HIV/AIDS is communicated about within the context of socio-cultural, economic, and agricultural transition that resulted, amongst other things, in a sharp decline in banana production. It is shown that for the Bahaya, HIV/AIDS is yet another ecological challenge that coincides with a decline in soil fertility, diminishing access to land, increased poverty, food and nutrition insecurity, and a lower production of their long-standing cultural and staple food. The paper examines some of the possible reasons why HIV/AIDS is referred to as ekiuka, a combination of pathogens that destroy bananas. The paper concludes that HIV/AIDS and banana plants are cognitively linked and that understanding how people communicate about HIV/AIDS is important for understanding how HIV/AIDS is connected to the Bahaya agricultural livelihood and for implementing effective alleviation strategies.
Dryland agriculture under rainfed conditions is found mainly in Africa, the Middle East, Asia, and Latin America. In the harsh environments of Sub-Saharan Africa (SSA) and West Asia and North Africa (WANA), water is the principal factor limiting crop yield. A review has been carried out on soil and crop management research that can increase the water use efficiency.The WANA production systems are dominated by cereals, primarily wheat in the wetter and barley in the drier areas, in rotation with mainly food legumes such as chickpea, lentil and forage legumes. The SSA production systems are generally characterized by cereal/legume mixed-cropping dominated by maize, millet, sorghum, and wheat. The major constraints in both regions to crop production are low soil fertility, insecure rainfall, low-productive genotypes, low adoption of improved soil and crop management practices, and lack of appropriate institutional support.Different cropping systems and accompanying technologies are discussed as well as selected examples of impact of these technologies. Results indicate that there is an advantage to apply these technologies but being function of socio-economic and bio-physical conditions. It is recommended that future research focuses on integrated technology development while taking into account also different levels of scale such as field, village, and watershed.
In organic agriculture the use of genetically modified organisms (GMOs) is banned. Recently, two novel breeding techniques have been developed, i.e., cisgenesis and reverse breeding, both of which are based on gene technology but should raise less moral concerns from the public. Whether the products of these breeding processes are classified as GMOs depends on the interpretation of the relevant EU regulations. In cisgenic plants, the genes introduced through genetic modification are from a crossable donor plant so that the source of the genes is considered to be of the same nature. In reverse breeding, the recombinant genes, essential to the breeding process, are no longer present in the product resulting from the entire breeding process, and thus the product as such is not transgenic. Should varieties obtained through cisgenesis or reverse breeding be allowed in organic agriculture? The answer to this question depends on whether the product or the process of breeding is taken into account. Assessment based on the product implies a choice of an ethical approach that only considers the extrinsic consequences of human action by making a risk-benefit analysis. It neglects so-called intrinsic, ethical arguments related to the applied technology (the process] itself. The organic movement uses the intrinsic argument of 'unnaturalness' against genetic engineering. We therefore conclude that products of cisgenesis and reverse breeding should be subject to the current GMO-regulations in organic agriculture and should thus be banned from organic agriculture.
The objections of organic agriculture against genetic engineering as presented in the 2002 Position Statement of the International Federation of Organic Agriculture Movements (IFOAM) are analysed. The objections can be grouped into three categories: risks to human health and the environment, socio-ethical objections, and incompatibility with the principles of sustainable agriculture. As to threats to human health and the environment it is argued that scientists contradict each other. Socio-ethical objections indicate that farmers should also be free to choose for or against genetic engineering and therefore the free-choice criterion needs to be specified. The argument of violating the independence of the farmer depends on the present economic situation (e.g. power of multinationals) and does not seem to be a consequence of genetic engineering as such. But as genetic engineering is mainly practised by multinational organizations the argument cannot be seen separate from the economic situation. Genetic pollution is a serious issue, but only because the organic movement is against genetic engineering on principle. Once the philosophical and ethical principles behind the organic concept of sustainability are specified (the third category), almost all the objections listed in IFOAM's Position Statement can be reformulated into good reasons for rejecting genetic engineering. The basic principles are: a holistic methodological approach to living nature, the self-organization (self-regulation) of living nature, and the integrity of living organisms.
The risk environment of farmers is changing. For example, price and production risks are increasing and governments increasingly encourage agriculture to find private market solutions for catastrophic risks like floods and epidemic diseases. We studied risk management strategies like insurance — in which risks are shared with others - to find out whether such strategies provide opportunities for farmers to deal with the new risks with which agriculture is confronted. We concluded, on both theoretical and empirical grounds, that risk-sharing strategies do provide such opportunities. From a theoretical perspective, because risk-sharing tools are in principle advantageous to both individual farmers and society as a whole, and from an empirical perspective, because farmers already perceive risk-sharing, especially insurance, as an important strategy to manage risks. The empirical results are based on a questionnaire survey among Dutch livestock farmers. Areas are identified for further research, amongst other things, with respect to risk-sharing strategies for price risks and epidemic livestock disease risks.
Catastrophic risks result in high losses in agriculture. To cope with such losses farmers need to apply risk management strategies to balance their profits and risks. Therefore risk assessment and risk modelling are important to support farm-level decision-making. This paper (1) reviews the techniques to elicit risk perception and risk attitude, and (2) describes how the simultaneous impact of risk perception and risk attitude could be accounted for in risk programming. Although inherent in catastrophic risks, objective data are sparse and eliciting subjective data is likely to be flawed. The review shows that the negative impact resulting from catastrophes cannot be ignored without compromising the optimal decision.
The concept of naturalness can be used to characterize organic agriculture and to distinguish it from conventional agriculture, provided naturalness not only refers to the non-use of synthesized chemicals, but also to the ecological and systemic principles, and to a respect for the integrity of living organisms. Examples of the implicit use of the integrity concept in agriculture will be described to show its practical aspects and implications. The (non-atomistic) holistic concept of integrity of organisms has been the subject of severe scientific criticism — specially from in essence ontological reductionists. In their view, an organism is essentially no more than a complex set of atoms and molecules and its integrity a non-concept. In order to reach scientific acceptance of the integrity concept and to support its use in organic agricultural practice, it needs further underpinning. In this article, based on a critical analysis of (a) ontological and methodological aspects of reductionism, and (b) expert knowledge and the process of pattern recognition and application, the validity of the holistic concept of integrity will be explored.
Average nitrate contents in carrots from randomly chosen farms in different years during the period 1996-2004.
It is debatable whether organic agriculture as a whole is conventionalizing, as historical data are almost absent. However, a short overview of a few organic sectors in the Netherlands shows that the influence of conventional agro-food commodity chains is increasing and that the use of off-farm inputs is high. So current practices in organic agriculture (OA) may have negative effects on issues like energy use, nutrient losses and recycling, even though the practices are compliant with the existing EU-regulation on OA. This reduces the distinguishability of OA, thereby threatening long-term market perspectives and public support. Whether conventionalization is problematic depends on the opinion of what ‘organic agriculture’ actually entails. It is argued that no conclusions can be drawn about core values of OA in a normative (ethical) sense from sociological research on values of various stakeholders and their motives for being active in the organic chain. Only normative values may function as a guide towards the future, inspiring practices in OA as well as long-term market perspectives and regulatory developments. The OA principles formulated by the International Federation of Organic Agriculture Movements (IFOAM) on ecology, health, care and fairness do provide such a normative value basis and appear to be firmly rooted in the values of OA identified in the literature. Looking at the consequences of conventionalization in some sectors of OA in the Netherlands, we can conclude that they conflict with all IFOAM principles, in some way, especially with the Principles of Ecology and Health. If the OA sector wants to adhere to these core values and promote long-term market perspectives as well as public support, a development is required that limits conventionalization or mitigates its negative effects. The use of off-farm inputs is an important factor in conventionalization itself and has negative effects on the core organic values. Given the influence of international trade and economic competition, this development will require regulative action at international level that is focused on a reduced use of off-farm inputs (either conventional or organic inputs transported over a long distance).
Producers, traders and consumers of organic food regularly use the concept of the natural to characterize organic agriculture or organic food. Critics sometimes argue that such use lacks any rational (scientific) basis and only refers to sentiment. We carried out research to (1) better understand the content and the use of the concepts of nature and the natural in organic agriculture, (2) to reconstruct the value basis underlying the use of the concept of the natural in organic agriculture, and (3) to draw implications for agricultural practice and policy. A literature study and the authors' own experience were used to produce a discussion document with explicit statements about the meaning of natural in the different areas of organic agriculture. These statements were validated by means of qualitative interviews with stakeholders. The concept of nature or the natural appeared to be value-laden. The value basis is a normative reconstruction that cannot just be derived from the use of the word natural by organic stakeholders. For this reconstructed concept the word naturalness is used. Naturalness thus becomes an ethical value for organic agriculture, an inspirational guide for organic stakeholders. The value of naturalness refers to a basic respect for the intrinsic value of nature, i.e., the value nature has, independent of the benefits it may have for humans. This manifests itself in three ways: (1) in the use of natural substances, (2) in respecting the self-regulation of living organisms and ecosystems, and (3) in respecting the characteristic (species-specific) nature of living organisms. If organic stakeholders limit themselves to using natural substances it is called the no-chemicals approach. If they also respect the self-organization of living organisms the authors call it the agro-ecological approach. If also the normative element of naturalness is included, it is called the integrity approach.
To address globalization challenges, the International Federation of Organic Agriculture Movements (IFOAM] articulated the principles of organic agriculture through a worldwide participatory stakeholder process. The process aimed to bridge the values from the pioneers of organic agriculture to the present time of globalization and to extended growth of the organic sector. As a result the principles of health, ecology, fairness and care are now worldwide considered as the basis from which organic agriculture grows and develops. IFOAM institutionalized these four principles in its own work, for example in the revision of the Organic Guarantee System. The four principles offer a perspective on how to deal with the challenges of globalization. A response to these challenges seems to be to extend and further detail the standards so that, for instance, externalities can be included. However, stricter standards may not do justice to the principle of fairness, as they potentially undermine fair access to markets. Ideal would be a situation in which a balance between the principles and standards can be realized.
The article examines the socio-cultural and political factors which affect the adoption of biological management of soil fertility in Javanese and Lampungese farming communities of the Province of Lampung, Indonesia. The research was carried out using a hybrid methodological framework, thus blending quantitative and qualitative analysis to provide a holistic picture of the agro-environmental and social conditions of the area. Analysis was carried out to identify relations between ethnic group and agro-ecological strategy. These strategies were then analysed and contrasted to assess the acceptability and possible constraints to the adoption of biological soil management. Land tenure issues and inter-community social dynamics are analysed and their impacts on long-term adoption of biological means of soil fertility management are investigated. Implications for policies and programme are drawn.
An analysis is made of the perception of ‘agrobiodiversity’ by 45 individuals being directly or indirectly involved in the Dutch agro-food chain. The analysis is based on an on-line stakeholder dialogue (OSD) entitled ‘Vision on Agrobiodiversity’ and 25 personal interviews. The OSD was held between October 1999 and May 2000 and generated 105 contributions. It was initiated to investigate the limited attention for and fragmented perception of agrobiodiversity. In the process we were confronted with basic causes for these attitudes. This study first considers the advantages of an OSD over traditional forms of professional dialogue, such as conferences and working groups. The results of the OSD lead us to the observation that Dutch policy-making on agrobiodiversity has been mainly motivated by international obligations and has involved a very limited number of stakeholders nationally. To be effective, such policy-making will: (a) remain problematic without a coherent view consensus on the role of agrobiodiversity in the overall organisation of agricultural production, and (b) require higher investments in discussing and communicating the relevance of agrobiodiversity with all relevant stakeholders in the agro-food chain.
Home gardens are important for enhancing food and nutritional security for HIV/AIDS-afflicted rural households through dietary diversity. Female-headed households may depend on home gardens more than average households to supply and supplement the household's diet when labour is constrained for field cropping. This paper compares household characteristics, dietary diversity, labour allocated to crop husbandry and home garden biodiversity amongst 22 HIV/AIDS-afflicted female-headed households, 15 non-HIV/AIDS-afflicted female-headed, 10 HIV/AIDS-afflicted dual-headed and 33 non-HIV/AIDS-afflicted dual-headed households in rural communities in the Eastern Region of Ghana. Information on household characteristics and labour allocation to home garden management was obtained through a cross-sectional survey and in-depth interviews. Dietary diversity score was estimated for each household based on a 24-hour qualitative dietary recall. Plant species in each home garden were recorded. HIV/ AIDS affliction did not affect home garden diversity but afflicted households had more on-farm sources of income and a higher dietary diversity and allocated more adult labour to home garden activities than non-afflicted households. Dual-headed households had more diversity in the home garden and allocated more adult male labour to the home garden than female-headed households. Statistically significant interactions between HIV/AIDS affliction and headship were observed for Shannon-Wiener index, number of crop species, number of annual crop species and number of root and tuber crop species in the home gardens: there were no headship effects when households were afflicted whereas dual-headed households had higher values than female-headed households in non-afflicted households. HIV/AIDS-afflicted households had significantly more annual crop species and more root and tuber crop species than non-afflicted households for female-headed households, whereas there were no significant differences for dual-headed households. Faced with confinement to the homestead in caregiving and by the obligation to ensure household food and nutritional security, HIV/AIDS-afflicted households spent more (female] labour on home garden management than non-afflicted households to produce crops for sustenance and dietary diversity.
This paper shows how HIV/AIDS negatively affects soil fertility management strategies among Kenyan smallholders. The paper examines this relationship, using ethnographic interviews of purposively selected affected households in Butula Division, Busia District, Kenya. Soil fertility management was given low priority in the face of high HIV/AIDS prevalence although it is a critical resource for meeting basic needs. Findings show that HIV/AIDS poses a significant and complex threat to the already deficient soil fertility management practices among smallholders. The disease's synergistic relation with poverty increases the stress on soil fertility management. It destructs local social structures and households by taking away resource persons, overburdening traditional insurance systems, and obliterating any modest capital and labour useful for soil fertility management that has been accumulated by the household. There is need for robust soil fertility policy-action frameworks that can be sustained under the limiting conditions of affected households and that can mitigate HIV/AIDS impacts amidst high poverty.
This paper explores the effects of HIV/AIDS on the livelihoods of banana-farming households in Maragua district, Central Kenya. It is based on the results of a field study carried out during 2004–2005. The study applied the sustainable livelihood approach, using both quantitative and qualitative methods of data collection. A survey was conducted among 254 farming households: 75 HIV/AIDS-affected households and 179 non-affected households. It was found that the people attribute the spread of HIV/AIDS in the area to rural-urban migration and hopelessness and despair due to lack of employment, especially among the youth. HIV/AIDS-affected households are mostly female-headed, have a significantly higher dependency ratio and experience labour shortage despite their larger size. A significant number of affected households have stopped growing labour-intensive cash crops and shifted to producing food crops. Management in banana farming has declined among these households. Affected households do not sell land to cater for household needs such as medical expenses and school fees, but use their savings or sell livestock instead. Additionally, leasing land and migration are important livelihood strategies of HIV/AIDS-affected households. Altogether the picture of HIV/AIDS effects on the livelihoods of banana-farming households is one of mixed evidence.
Alfalfa stem internodes of advanced maturity were used to examine the variability among tissues for rate and extent of cell-wall degradation by rumen microorganisms. Thin sections (100 μm) were incubated with rumen fluid in vitro for 0, 2, 4, 8, 16, 24, 48, 72, and 96 h. The degradation of tissue cell walls was evaluated for each fermentation time interval against a nondegraded mirror control section by light microscopy. Cell-wall thickness of alfalfa stem tissues was measured using scanning electron microscopy for both control and fermented sections. Rate and extent of cell-wall degradation were calculated from these measurements. Non-lignified epidermis, collenchyma, chlorenchyma, cambium and primary xylem parenchyma were rapidly and completely degraded within the first 8 h of fermentation. Rates of degradation ranged from 0.04 μm h−1 for thin-walled (0.29 μm) primary xylem parenchyma tissue to 0.11 μm h−1 for thick-walled (0.90 μm) collenchyma tissue. The non-lignified secondary wall (1.70 μm) of the primary phloem fibres required 24 h for complete degradation. Cell walls of some lignified tissues (e.g. pith parenchyma and secondary xylem fibres) were only partially degradable (9.1 to 65.5 %) even after 96 h of fermentation. The primary and secondary xylem vessels appeared to be completely nondegradable. The observed rates of cell-wall degradation for nonlignified alfalfa stem tissues were two to five times faster than previously estimated for nonlignified grass mesophyll tissue. However, extent of degradation for the lignified tissues of alfalfa stems was less than reported for lignified grass stem sclerenchyma. These differences in cell-wall degradation characteristics among tissues within alfalfa and compared to grasses are probably related to cell-wall lignification and polysaccharide composition of individual tissues.
Both food- and environmentally-related allergies are a continually growing health problem, particularly in the western world. The exact causes and the additional environmental and social factors that play a role in the onset of these illnesses are still poorly understood. While sufferers of allergy remain a minority in society, the reduction of their quality of life and the financial consequences for society as a whole are of major significance. Allergy is an illness that confronts the sufferer on a daily basis with his or her life style limitations. The direct and indirect annual costs to society (medical care, sick leave, loss of earnings, reduced productivity] are already running well into billions of euros. A complicating factor is that there are many kinds of allergy, with many different causes, requiring several approaches for treatment. There is no single solution. Much social and scientific research is still needed to generate additional knowledge required to determine a suitable multidisciplinary strategy for the long-term tackling of this problem. Input from a wide range of sources, including social scientists, medics, agronomists and immunologists, is essential to fully assess the situation and to assist in determining long-term policy decisions at a national level. This multidisciplinarity calls for broad support from different sections of government, industry and societal bodies to achieve the desired goal of reversing the rise in the number of allergy sufferers, preferably through prevention rather than cure. In this article we present the most salient items from the presentations and discussions of a workshop on the agronomic approaches to allergy prevention, recently held in the Netherlands.
Denitrification and leaching of nitrogen (N) from agriculture are a loss of nutrients to farmers and sources of pollution to water and air, and should therefore be minimized. In a field experiment on loamy soil, denitrification and N leaching were measured after late summer incorporation of fodder radish residues with or without paper pulp as N-immobilizing organic material. A set of relatively simple methods were used to measure and calculate denitrification and N leaching during the first two weeks after application and during the rest of the winter period. The methods were acetylene inhibition of nitrification, anion-exchange resin, the mineralization model MINIP, and inorganic-N balance calculations. Paper pulp increased N immobilization after the first day of application throughout the winter. This led to a 63–70% reduction in N losses compared with the sole fodder radish field and with the control. Denitrification was highest in the sole fodder radish treatment, at 65% of its total N losses. N leaching during the winter period was highest in the control, at 70% of its total N losses. This N was mainly liberated by mineralization of soil organic matter after ploughing in late summer. The application of paper pulp plus fodder radish did not affect sugar beet yields in the next year. The methodology for determining leaching and denitrification enabled the assessment of differences among treatments. It showed clearly that paper pulp strongly reduced N losses on this type of soil. The anion resin method that was used to measure leaching during the winter period showed clear and consistent differences between treatments, but may need additional calibration before fully relying on the absolute amounts of N leached.
Given that freedom of movement improves sows' welfare, the implications for the emission of ammonia of keeping sows in groups instead of individually were investigated. Three housing systems were compared: System A, with 64 sows kept individually in feeding stalls with 2.8 m2 surface area per sow; System B, with 62 group-housed sows, free access stalls with 3.3 m2 surface area per sow; System C, with 65 group-housed sows, electronic sow feeders and with 3.4 m2 surface area per sow. The sows in Systems A and B were fed simultaneously twice a day at 7:30 and 15:30 h. In System C the sows were fed sequentially once a day from 15:30 h onwards.The study was carried out in winter during three one-week periods. Average outdoor temperature was 3.7 °C. The average ambient temperatures recorded in the houses were ther-moneutral: 19.8 °C for System A, 19.2 °C for System B and 19.0 °C for System C. The average ammonia emission per sow was 0.72, 0.62 and 0.70 g hour−1 for the systems A, B and C, respectively. For the systems A, B and C this implied that 23, 20 and 23% of the nitrogen intake was emitted as ammonia nitrogen, respectively. The emission from System B was significantly less (P<0.05). The diurnal pattern of the ammonia emissions from Systems A and B were biphasic and were related to feeding times. In System C the diurnal pattern had a more monophasic course related to the feeding time in the afternoon with an additional small peak in the morning after the lights were switched on.The diurnal pattern of ammonia emission from sow houses was related to the feeding schedule. Under thermoneutral conditions, giving sows a larger area at their disposal — such as with group housing — did not imply an increase in ammonia emission.
To predict ammonia (NH3) volatilization from field-applied manure, factors affecting volatilization following manure application need to be known. A database of field measurements in the Netherlands was analysed to identify factors affecting the volatilization from manure applied to grassland by various techniques, and to quantify their effects. The application techniques were broadcast surface spreading, narrow-band application, and shallow injection. External factors considered were weather conditions, manure characteristics, soil type and soil moisture content, and grass height. Narrow-band application and shallow injection significantly reduced NH3 volatilization, compared with broadcast surface spreading. The mean cumulative volatilization for surface spreading was estimated to be 77% of the total ammoniacal nitrogen (TAN) applied, 20% for narrow-band application and 6% for shallow injection. The TAN content of the manure, the manure application rate and the weather conditions significantly influenced the NH3 volatilization rate. The volatilization rate increased with an increase in TAN content of the manure, manure application rate, wind speed, radiation, or air temperature. It decreased with an increase in the relative humidity. The identified influencing factors and their magnitude differed with the application technique. Grass height affected NH3 volatilization when manure was applied in narrow bands. The results show that external factors need to be taken into account when predicting ammonia volatilization following manure application.
One of the key concerns of biogas plants is the disposal of comparatively large amounts of digestates in an economically and environmentally sustainable manner. This paper analyses the economic performance of anaerobic digestion of a given biogas plant based on net present value (NPV) and internal rate of return (IRR) concepts. A scenario analysis is carried out based on a linear programming model to identify feedstocks that optimize electricity production and to determine the optimal application of digestate. In addition to a default scenario, management and policy scenarios were investigated. Economic evaluations of all scenarios, except no subsidy scenario, show positive NPV. The highest NPV and IRR values are observed under reverse osmosis (RO) as a green fertilizer scenario. Our findings show that treating RO as a green fertilizer, as opposed to manure (default scenario), is not only lucrative for the plant but also lessens environmental burden of long distance transportation of concentrates. This paper also concludes that given the uncertainty of regulations concerning RO and the currently low values of digestate and heat, high investment and operating costs limit feasibility of anaerobic digestion of wastes of farm origin and other co-substrates unless subsidies are provided.
Environmental flows are of crucial importance for questions of sustainability. But analysing only the material side of environmental flows brings us half way understanding questions of sustainability. This article reports on the development of a more integrative approach in studying environmental impacts of agro-industrial systems in Asia, taking tapioca (cassava starch) processing in Vietnam as an example. The analysis of material flows and technological options to close material cycles is combined with an actor-network analysis from three angles: a policy, an economic and a social perspective, respectively. The paper finally assesses the additional value of the developed methodology and points out ways for further investigation and development of a more integrative approach to industrial transformations.
Toxoplasma seroprevalence in the Dutch population by age groups in the years 1987 
Toxoplasma infection in Dutch slaughter pigs in the period 1969-2001. 
Toxoplasmosis is still one of the most common parasitic infections in the world, although in Europe improvements in hygiene and the introduction of ‘total’ indoor farming in livestock production have rapidly diminished the problem during the past decades. As a result of public dislike, however, introduction of alternative and more acceptable animal-friendly livestock production systems including outdoor access are gaining ground. Potentially these systems can lead to increased prevalence of certain zoonotic diseases, including Toxoplasmosis. To retain prevalence of this disease in humans at current levels, emphasis should be on disease control at farm-level. This article provides an analysis of various risk factors for farm animals to get infected with Toxoplasma gondii. Access of cats to the farm premises, the use of compost and goat whey, and rodent control were identified as possible risk factors that should be addressed. Consumers should be aware of the fact that Toxoplasma infection, besides through meat, can also be caused by the uptake of contaminated water, soil, fruit and vegetables.
The performance of a white clover based dairy system in comparison with a grass/fertiliser-N system was studied during three years. Both systems had 59 cows, plus young stock, on an area of 40.6 ha for grass/clover and 34.4 ha for grass/fertiliser-N.During the grazing season, the cows in both groups were supplemented with 3.5 kg concentrates day−1. The daily Fat and Protein Corrected Milk (FPCM) production was 25.7 and 26.5 kg cow−1 for grass/fertiliser-N and grass/clover, respectively. The difference in milk production occurred from July onwards. Despite preventive measures in the grass/clover system, bloat occurred several times between August and October. During the housing season, cows received ad libitum grass or grass/clover silage with 6 kg concentrates cow−1 day−1. Although the intake of grass/clover silage was consistently higher, there were no differences in milk production.The grass/clover system had a lower N surplus, but this was related to the lower intensity of the system. The overall N utilisation was 25% in both systems. The average nitrate concentration in drain water, measured on a selection of fields, was 26 and 28 mg 1−1 for grass/fertiliser-N and grass/clover, respectively. The nitrate concentrations in drain water from grass/clover fields were positively related with the clover content in the sward. The energy use of the grass/clover system was 15% lower than that of the grass/fertiliser-N system, with the fertiliser use as the main source of difference. Compared to the grass/fertiliser-N system, the gross margin per cow was slightly higher for grass/clover, but the gross margin per ha was 10% lower for grass/clover.Considering agronomic and environmental aspects only, white clover based dairy systems are a viable option for the future, but from a financial viewpoint the use of white clover will be restricted to systems which produce approximately 12 t FPCM ha−1 year−1 or less.
Animal welfare issues may involve different species and require decision-makers to compare welfare across species. Up to now applied ethologists have largely ignored questions involving cross-species comparisons. This paper discusses the question whether cross-species comparisons about animal welfare can be provided with a scientific basis, i.e., based on scientific arguments. The arguments pro and contra are reviewed. Conceptually, cross-species comparisons should be possible, but at the explanatory and operational levels substantial problems remain to be resolved. An example is given comparing the welfare of laying hens in battery cages, conventionally housed fattening pigs, conventionally housed broilers and dairy cattle at pasture. Possibly a method could be developed that makes welfare assessments across species more transparent and coherent, and that is based on available scientific information. An outline of such a method is described in this paper.
Organic livestock production is a means of food production with a large number of rules directed towards a high status of animal welfare, care for the environment, restricted use of medical drugs and the production of a healthy product without residues (pesticides or medical drugs). The intentions of organic livestock production have been formulated by the International Federation of Organic Agriculture Movements (IFOAM) and were further implemented by EU regulation 2092/91 in the year 2000. The consequences of these rules for the health of the animals were not yet fully anticipated at the time these regulations were made and it has become clear that in some cases the rules are not clear enough, thereby even hampering the development of the production system. In this review we shall discuss the implications of these rules for animal health, whereby we shall focus on pig, poultry and dairy production systems. Disease prevention in organic farming is based on the principles that an animal that is allowed to exhibit natural behaviour is not subject to stress, is fed optimal (organic) feed, and will have a higher ability to cope with infections than animals reared in a conventional way. Fewer medical treatments would thus be necessary and if an animal would become diseased, alternative treatments instead of conventional drugs should be preferred. Although homeopathy or phytotherapy are recommended according to prevailing regulations, not many organic farmers use this treatment regimen because of lack of scientific evidence of effectiveness. Important health problems in organic livestock farming are often related to the outdoor access area, exposing the animals to various viral, bacterial and parasitic infections some of which may only influence the animals' own welfare whereas other ones may also endanger the health of conventional livestock (e.g. Avian Influenza) or pose a food safety (Campylobacter, Toxoplasma) problem to the consumer. Many preventive measures can be taken, such as using better animal breeds, optimized rearing conditions, pre- and probiotics, and addition of acids to the drinking water. In case of infectious disease, tight vaccination schedules may prevent serious outbreaks.
This review discusses animal welfare effects of providing an outdoor run to laying hens. Compared with barn systems, the provision of an outdoor run leads to higher space allowances, a higher number and diversity of behavioural and physiological stimuli, and freedom to change between different environments with for instance different climatic conditions. Evidence is presented that these factors may have positive welfare effects for the hens, although, due to the complex interaction with other factors, this is not necessarily always the case. Outdoor runs may, at the same time, impose increased welfare risks associated with an increased contact with infectious agents, greater difficulties to maintain good hygienic standards, possibly imbalanced diets and predation threats. Measures to limit these welfare risks and to take full advantage of the potentials of outdoor runs include restriction of group size, keeping cockerels with the hens, hygienic measures including rotation of runs, providing well-dispersed covers, as well as appropriate pullet rearing and breeding strategies. Fully mobile housing systems provide a promising integrated approach to concurrently implement a number of effective measures. However, it is concluded that too little research and not enough resources went into solving the problems presently besetting free-range systems and that it, therefore, would be premature to make a final judgement now on welfare effects of outdoor systems in comparison with pure indoor systems.
The veterinary antibiotic tylosin was administered to broilers at sub-therapeutic and therapeutic levels to study its effect on the quality of poultry breast meat. No statistically significant differences were observed in moisture content, pH, drip loss, colour and extent of lipid oxidation between the breast meat from treated and not treated birds. However, the cooking loss of the meat from the birds administered tylosin was significantly higher than that from the not treated ones. Additionally, the mean shear force of the breast meat was significantly lower for the sub-therapeutically treated broilers than for the not treated and the therapeutically treated ones. It was concluded that the level at which tylosin was administered to the broilers affected the quality of the breast meat, particularly its textural properties.
A study was done that aimed at designing biodiverse crop production systems for the Netherlands taking into account the views held by stakeholders in society. Biodiverse crop production systems contain different species and/or different genotypes within a species, leave room for other plants (both spontaneous and sown plant species) and enhance the associated biodiversity of microfauna, mesofauna and microflora. The study was carried out jointly by closely co-operating scientists in the fields of agronomy, environmental sciences and social sciences. To integrate the knowledge of specialists and stakeholders a stakeholder consultation was done consisting of a literature review analysing the Dutch policy on biodiversity, a workshop consulting intermediary institutes about their views on arable biodiversity, and an expert panel that not only monitored the design process but also regularly discussed the developments during a three-year field test of a highly diverse production system that meanwhile was designed. The results of the study were used to compare the design with other production systems. In addition, a list of indicators was compiled to test this design for system performance in terms of societal (people), ecological (planet) and economic (profit) aspects. Finally, through this study, choices in the design process were made explicit and research topics were identified to test performance of the resulting system.
In a companion paper, a theoretical framework for the application of the Mitscherlich equation to describe nutrient response for rainfed crop production is presented. Water-limited potential, or maximum, yield is assumed to be a linearly increasing function of seasonal rainfall. In addition, the quantity of nutrients required by a crop to achieve water-limited potential yield and the nutrient availability are also expressed as functions of seasonal rainfall. This rainfall-dependent Mitscherlich equation is evaluated using data from agronomic (nitrogen × phosphorus) experiments conducted under rainfed conditions in the semi-arid region of Syria. The analysis showed that rainfall explained most of the variation in yield between locations and seasons, but that the moisture-dependent nutrient part of the Mitscherlich equation explained a small but significant part of the yield variation as well. The model discussed in this paper appears to provide a framework for a Mitscherlich-type approach to describing crop response to nutrient availability c.q. fertilizer application under rainfed conditions in the semi-arid regions.
Top-cited authors
Paul C Struik
  • Wageningen University & Research
Laurens Klerkx
  • Wageningen University & Research
Emma Jakku
  • The Commonwealth Scientific and Industrial Research Organisation
E.T. Lammerts van Bueren
  • Wageningen University & Research
C. Leeuwis
  • Wageningen University & Research