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To study in vivo digestibility of forages from semi-natural grasslands two experiments were carried out. In the first experiment lactating dairy cows were offered three different silage-based diets. Silage originated from intensively managed grassland (IM), extensively managed species-poor grassland (SPP), or extensively managed species-rich grassland (SPR). In the second experiment lactating dairy cows were offered IM or a diet in which part of the IM had been replaced by 20% SPP (20SPP), 60% SPP (60SPP) or 60% SPR (60SPR). Intake was significantly lowest on diets with SPP, but intake on diets with SPR was not significantly lower than intake on IM. In both experiments gross energy and in vivo digestibility of organic matter, crude protein and neutral detergent fibre were highest for IM. In the first experiment SPP had a significantly higher digestibility than SPR, but in the second experiment differences in digestibility between 60SPP and 60SPR were not statistically significant. In both experiments in vivo digestibility was almost similar to in vitro digestibility, but no suitable equation could be found to estimate in vitro or in vivo digestibility from the chemical composition. Although digestibility and crude protein content were significantly lower for SPR than for SPP, intake of digestible organic matter appeared to be higher. It was concluded that there appears to be more scope for silage from extensively managed species-rich than for silage from extensively managed species-poor grassland

By 1 January 2004, as a result of EU-regulation 2092/91 for organic farming, the organic sector needs to have developed efficient schemes to be able to use adequate quantities of organically produced seed and planting material. Market problems and agronomic problems that are related to obtaining sufficient quantities of adequate quality are reviewed. For successful production of organic seed and planting material intensive communication between and mutual commitment of farmers, traders, breeders and governmental organizations are necessary. Farmers together with traders should be involved in variety testing and in designing crop ideotypes by identifying the desired cultivar(s) and variety traits. Breeders can contribute by incorporating the desired organic traits in future breeding programmes. In addition, a great effort is needed to develop empirical knowledge and research-based information on adapting and improving cultural practices for organic seed production, developing resistant cultivars for healthy seed production, developing protocols for seed health testing, assessing disease threshold values, and designing organic seed treatments. The EU-regulation should be strictly enforced, no longer allowing derogation of the use of conventional seeds after 2003 for those crops for which diverse, high quality seed or planting material of organic origin is available. It is expected that by 1 January 2004 enough seed or planting material will be available for most crops. But continuous optimizing of organic seed production management will be required to enlarge the cultivar assortment and to control the quality of organic seed and planting material

By 1 January 2004, as a result of EU-regulation 2092/91 for organic farming, the organic sector needs to have developed efficient schemes to be able to use adequate quantities of organically produced seed and planting material. Market problems and agronomic problems that are related to obtaining sufficient quantities of adequate quality are reviewed. For successful production of organic seed and planting material intensive communication between and mutual commitment of farmers, traders, breeders and governmental organizations are necessary. Farmers together with traders should be involved in variety testing and in designing crop ideotypes by identifying the desired cultivar(s) and variety traits. Breeders can contribute by incorporating the desired organic traits in future breeding programmes. In addition, a great effort is needed to develop empirical knowledge and research-based information on adapting and improving cultural practices for organic seed production, developing resistant cultivars for healthy seed production, developing protocols for seed health testing, assessing disease threshold values, and designing organic seed treatments. The EU-regulation should be strictly enforced, no longer allowing derogation of the use of conventional seeds after 2003 for those crops for which diverse, high quality seed or planting material of organic origin is available. It is expected that by 1 January 2004 enough seed or planting material will be available for most crops. But continuous optimizing of organic seed production management will be required to enlarge the cultivar assortment and to control the quality of organic seed and planting material

Enset (Ensete ventricosum) production is declining, and it faces genetic erosion due to drought, diseases and population pressure. Participatory Rural Appraisal (PRA) and additional formal survey studies on 315 households were conducted over three consecutive years (1998–2000) in the Sidama, Wolaita and Hadiya ethnic regions of southern Ethiopia to assess traditional cultivation methods, analyse the production systems, and evaluate farm-based enset biodiversity. The regions differ in terms of cultural background, resources, farming systems, population density, and agro-ecology. Furthermore, the methods for initiating suckers and the frequency of transplanting vary among the three regions. Diverse enset landraces were identified in the Sidama (52), Wolaita (55) and Hadiya (59) regions. Sidama farmers had the highest number of landraces per farm, 57nd 21␖ore than found on Wolaita and Hadiya farms respectively. In all three regions, landrace diversity was influenced by household resources, cultural background, population pressure, and agro-ecology. There were significant differences in the average number of enset landraces and livestock between rich and poor households in the three regions. Rich farmers had more land and manure-producing livestock, and they planted more enset landraces than did poor farmers. In all three regions, women proved to be more experienced than men in identifying enset landraces. The number of enset landraces per farm was significantly correlated with other household characteristics for resource-rich Sidama farmers and with the number of livestock and area of farmland for resource-rich Hadiya farmers. This suggests that middle-income or poor farmers concentrate on annual crops, rather than on growing the perennial enset plant. More research is needed to identify, characterize and conserve genetic diversity, and to improve the cultivation practices for enset. The cultural, socio-economic, and gender-associated aspects of enset cultivation need

Keywords: Salak, Salacca zalacca, Palmae, dioecious, haustorium, simple leaf, compound leaf, sucker, phyllotaxis, seedling, inflorescence, fruit, hand pollination, farm yard manure, fertilizer, shading, walking palm.Salak is a dioecious, suckering palm, grown for its fruit, mainly in Indonesia. Traditionally, plants are raised from seed and planted in market gardens under the shade of existing trees. Crop care is largely limited to roguing of most male plants, cutting excess suckers and ageing leaves, and hand pollination. Each production centre mainly grows its own favoured variety, but in the 1990s 'Pondoh', originally from Yogyakarta, became popular also elsewhere. Yield varies widely (say 5 - 13 kg per plant per year). A better understanding of the crop can presumably greatly increase yield levels. This fits in with Indonesia's strategy to develop fruit growing with a view to improving nutrition and increasing exports. Salak is one of the fruit crops selected under this strategy. This thesis reports explorative research on the agronomy and botany of the crop.AgronomyIntensive pollination of this dioecious species leads to heavy fruit and seed set. Seed shape is determined by the number of seeds per fruit. A correlation between seed shape and sex of the seed as assumed by salak growers in Indonesia is unlikely.Pollination and pollen quality influence both quality and quantity of the fruits. Choice of pollen depends on the cultivar to be pollinated.Salak seed is recalcitrant and endosperm plays an important role in germination. Without endosperm the embryo is unable to grow and develop. Storage of salak seed in charcoal can sustain its viability and enhance seedling growth compared to storage in ambient air or even in sawdust.Germination of salak seeds was retarded when planted in heavy soils. Organic matter is needed to improve the physical properties of the soil, particularly of heavy soils. A higher organic matter content also increased N and P levels in the so

Key-words : crop ideotype, genetic diversity, integrity of plants, intrinsic value, isophenic line mixture varieties, organic plant breeding, organic farming, organic propagation, participatory plant breeding, variety characteristics, seed-borne diseases, seed quality, spring wheat, threshold values, variety concept, variety mixtures. The organic farming system differs fundamentally from conventional agriculture in the management of soil fertility, weeds, diseases and pests. Organic farmers depend greatly on conventionally bred and produced varieties, but require varieties better adapted to organic farming systems for further optimisation of organic agriculture. This includes a greater need for 'reliable' varieties contributing to higher yield stability.In this thesis the concept of 'naturalness' as applied in organic agriculture is elaborated and used as guide to develop concepts and strategies for organic plant breeding and propagation. It refers to ecological and ethical principles, including thenon-chemical and agro-ecological approach, but also takes integrity of life into account.Based on these approaches the organic farming system is described and a general crop ideotype is defined. In the long run organic agriculture can only gain further progress when the genetic basis is renewed and broadened, and when the selection process is conducted under organic farming conditions. For self-fertilisers most promising seems the concept of (isophenic) line mixture varieties, composed of lines being phenotypically uniform but genetically heterogeneous. The ability to produce healthy seed under organic conditions should also be included in the variety ideotype. Further research is needed to develop protocols for seed health testing, to assess threshold values for seed-borne diseases and to design organic seed treatments.To improve the transparency in the discussions on the ethical aspects in organic agriculture concerning the assessment of the suitability of the bree

Currently, organic farmers largely depend on varieties supplied by conventional plant breeders and developed for farming systems in which artificial fertilizers and agro-chemicals are widely used. The organic farming system differs fundamentally in soil fertility, weed, pest and disease management, and makes higher demands on product quality and yield stability than conventional farming. Organic farming systems aim at resilience and buffering capacity in the farmecosystem by stimulating internal self-regulation through functional agrobiodiversity in and above the soil, instead of external regulation through chemical protectants. For further optimization of organic product quality and yield stability new varieties are required that are adapted to organic farming systems. The desired variety traits include adaptation to organic soil fertility management, implying low(er) and organic inputs, a better root system and ability to interact with beneficial soil micro-organisms, ability to suppress weeds, contributing to soil, crop and seed health, good product quality, high yield level and high yield stability. In the short run, organic crop ideotypes per crop and per market segment can help to select the best varieties available among existing (conventional) ones. However, until now many of the desired traits have not received enough priority in conventional breeding programmes. Traits like adaptation to organic soil fertility management require selection under organic soil conditions for optimal results. The limited area of organic agriculture will be the bottleneck for economic interest in establishing specific breeding programmes for organic farming systems. The proposed organic crop ideotypes may benefit not only organic farming systems, but in the future also conventional systems that move away from high inputs of nutrients and chemical pesticides

Keywords: Sustainable farming systems, Agronomic efficiency, Economic efficiency, Environmental efficiency, Sustainability index, Interdisciplinary analysis.The objective of the research described in this thesis was to determine what role improved agronomic efficiency can play in the transition towards more sustainable production systems. Agronomic efficiency measures the technical performance. If it could be improved, environmental damage could be reduced while, at the same time, economic performance could be improved. The latter is an important condition for a successful transition to sustainable agriculture.Because economists and agronomists use different concepts and assumptions, they disagree about the efficiency that should be feasible in practice. Therefore, first a conceptual model integrating agronomic and economic concepts was developed. The model presents a division into production levels and accompanying production restricting factors. The hypothesis that improved agronomic efficiency also improves sustainability was tested empirically for sugar beet growing. A positive correlation was indeed found between agronomic efficiency and sustainability. Next, the effect of some production restricting factors on the agronomic efficiency was assessed, using a model that simulated crop growth and water and nitrate processes in the soil to assess the effect of annual variation in weather on the efficiency. It was found that efficiency decreased by 13% due to variation in weather (including indirect weather effects). When the effect of differences in management was measured in an experiment using an interactive simulation model, socio-psychological factors were found to restrict the efficiency by 50-70%. Finally, using these results, the conceptual model was completed quantitatively. The refined conceptual model suggests that the differences between the theoretically-assessed efficiency levels are considerably smaller than the differences between 'average' and 'best

Keywordsbotanical composition, carbon, cutting frequency, dairy system, energy, fixation, gross margin, herbage quality, milk production, MINAS, nitrate leaching, nitrogen, nutrient balance, nutrient efficiency, perennial ryegrass, phosphorus, rotational grazing, soil, strategic nitrogen application, sward utilisation, white clover The present efforts to reduce the nitrogen (N) losses on dairy farms have reduced the use of fertiliser N and consequently renewed interest in white clover ( Trifolium repens L.).The general objective of this thesis was to provide a scientifically sound basis for the use of white clover on dairy farms in the Netherlands. The research consisted of a system comparison between a traditional grass/fertiliser-N system and a new grass/clover system. The aim was to design and demonstrate an agronomically, environmentally and economically sound white clover-based dairy system, and to identify potential problems with the utilisation of white clover in dairying. Simultaneously, specific research questions on processes within the new grass/clover system were addressed in separate field experiments with detailed measurements. The field experiments aimed to quantify the potential herbage yield and herbage quality of mixed swards, under a range of management practices, such as N and phosphorus (P) application, and cutting and grazing management.Both the clay and sandy soils in the experiments showed a good potential for perennial ryegrass/white clover swards with average annual DM yields of 13.3 t ha -1, respectively. The yields were among the highest recorded for unfertilised mixed swards in the Netherlands.The year-round application of N is not considered to be economic, but N can be used effectively on grass/clover swards if its use is restricted to spring application. This so-called 'strategic' application of N increases the DM yield in the first cut, only temporarily reducing white clover content in the sward. Phosphorus application did not i

This thesis describes the results of an analysis of the major developmental events taking place during the life cycle of the potato, based on records from 250 genotypes, from the highly diverse CxE population. The aim was to generate a massive amount of data to build a framework of crop physiological relationships, and use the data to begin with the identification of genetic factors controlling major developmental processes like senescence.Physiological ageing of seed tubers during storage influences tuber initiation and plant development. Since the majority of the CxE population had short or no tuber dormancy, seed tubers sprouted during storage. Physiological ageing is associated with the intensity of sprouting during storage and with tuber formation after planting. Therefore, it was necessary to investigate the association between sprout length, as an indicator of physiological ageing, and the timing of occurrence of events related to tuber formation and the duration of the plant cycle. Among genotypes of the CxE population, sprout length at the end of the storage period was not strongly related to tuber initiation or other events related to tuber formation. Associations were not found between sprout length and the duration of the plant cycle, plant size and several other variables recorded. We conclude that the variation in sprouting of seed tubers was not the main factor responsible for the large variation observed in the CxE population in the timing of occurrence of tuber formation and plant developmental events.Despite the large variation found in the CxE population and control varieties in the duration of the plant cycle, all began to form stolons and to flower within a remarkably short period of time. Results strongly suggest that the onset of stolon formation and flowering are not necessarily triggered by an environmental stimulus. The peak production of stolons and swelling stolon tips took place during flowering. However, while in most genotypes, stolon

Keywords : Enset, staple, indigenous knowledge, genetic diversity, AFLP, characterisation, conservation, Leaf Appearance Rate, Radiation Use Efficiency, yield potential, transplanting, leaf pruning, fermentation, 'kocho', food security The indigenous enset-farming complex of the south and southwestern highlands of Ethiopia has supported a higher population density than any other farming system. Enset ( Ensete ventricosum (Welw.) Cheesman) has been cultivated as (co-)staple food for about 7-10 million people. Since the last three decades, however, because of population pressure, recurrent drought and diseases there has been degradation of natural resources and, thus, the system failed to sustain the population. In the study, described in this thesis, the indigenous enset production methods, farm-based enset biodiversity and the plant characteristics and environmental factors influencing productivity were analysed to identify yield potentials and constraints in Sidama, Wolaita and Hadiya. The ultimate goal was to develop improved agronomic practices and enhance the use of the existing genetic diversity to reduce the gap between the actual yield and yield potential.Some indigenous cultivation methods vary among regions: initiation of suckers, frequency of transplanting, leaf pruning and planting patterns. Morphologically diverse enset clones were identified in Sidama (52), Wolaita (55) and Hadiya (59). Among 146 clones, a total of 180 AFLP fragments was scored of which 104 (58%) appeared polymorphic. The AFLP-based dendrogram showed more duplication groups than the farmers' characterisation method suggesting that farmers overestimate the genetic diversity. The correlation between the two methods was only weak. Yet, the comparison between the AFLP-based and farmers-based characterisation methods showed that some aspects such as absence of clear regional clusters and clustering of clones with various prefixes to a single group corresponded well. Duplications in the

Glycoalkaloids are secondary metabolites that are characterised by an undesirable taste, and which are known to be toxic when consumed in large quantities. Some wild potato germplasms that are used for the introgression of genes encoding heat tolerance contain high concentrations of glycoalkaloids in the tubers. Breeding and selection should therefore take place to lower the glycoalkaloid content in potato tubers and DNA markers can significantly facilitate the selection process.    This study was designed to identify DNA markers associated with the total content of glycoalkaloids (TGA) in the potato tuber. Two segregating resource populations were constructed, one of 216 clones using the tetraploid clones Cara and LT7 as parents and one of 176 clones using the tetraploid parents NT8 and LT7. The two populations were characterised by divergent TGA-content of the parental clones, where LT7 was the mutual male parent with high TGA-content, and both Cara and NT8 the parental clones with low TGA-content. The populations were used, in replicates, to estimate genetic parameters for total glycoalkaloid (TGA) content in the tubers.    Besides TGA-content in the tubers, over thirty other agronomic and morphological traits were assessed for genetic characterisation of the two populations used. Among agronomic traits assessed were tuber dormancy, tuber weight and tuber number. Several traits were calculated based on data obtained, such as tuber size distribution and tuber number distribution. Morphological characteristics assessed included plant height, number of nodes on the main stem, and terminal leaflet shape.    In both populations, the parental clones differed markedly in TGA-content and the progeny population was normally distributed for this trait after logarithmic transformation. Broad sense heritability estimates for TGA-content were 0.54 in CaraxLT7 and 0.50 in NT8xLT7 and the trait proved to be inherited in a non-dominant manner. The m

This paper first looks at the changes in agricultural research structures, research questions and research culture in the Netherlands. In the context of these changes, the future scope, readership and editorial policy of the Netherlands Journal of Agricultural Science are discussed

Development of hemp cultivation in the Netherlands and the United Kingdom

Description of the development of hemp cultivation in Europe