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At the moment, there are a large number of agricultural net types on the market characterized by different structural features such as type of material, type and dimensions of threads, texture, mesh size, porosity / solidity and weight; by radiometric properties like color, transmissivity/reflectivity/shading factor; by physical properties like air permeability and several mechanical characteristics such as tensile stress, strength, elongation at break, and durability. Protection from hail, wind, snow, or strong rainfall in fruit-farming and ornamentals, shading nets for greenhouses and nets moderately modifying the microenvironment for a crop are the most common applications. A systematic review of the current state-of-the-art of structural parameters, standard and regulations, most common agricultural net applications, and their supporting structures has been developed by means of a literature study, technical investigations, concerning characteristics and use of nets. As a result, the survey highlighted that in many cases different, not even similar, net types were adopted for the same application and the same cultivations by various growers. Results show that neither growers nor net producers have clear ideas about the relationship between the net typology optimization for a specific application and the construction parameters of the net. The choice often depends on empirical or economic criteria and not on scientific considerations. Moreover, it appears that scientifically justified technical requirements for nets used in specific agricultural applications have not been established yet.

A computer model for welfare assessment in laying hens was constructed. This model, named FOWEL (fowl welfare), uses a description of the production system as input and produces a welfare score as output. To assess the welfare status a formalized procedure based on scientific knowledge is applied. In FOWEL the production system is described using 25 attributes (space per hen, beak trimming, free range, etc.), each with two or more levels, together defining the characteristics of a production system. A weighting factor is used for each attribute, based on the available scientific knowledge of the effects of the attribute levels on the welfare aspects. The welfare score of a production system results from the attribute levels combined with the weighting factors. The results show that feeding level, space per hen, perches, water availability and nests were the most important attributes. The attribute free range was of minor importance. FOWEL includes a description of 22 production systems. The welfare score of cage systems was low, of barn and aviary systems medium, and of organic systems high. The presence of a free range resulted only in a small improvement in the welfare score. De auteurs beschrijven een computermodel dat de bijdrage van specifieke elementen van de huisvesting op de gezondheid en welzijn van hennen in diverse productiesystmen, inclusief het nut van een uitloopren, analyseert

In this paper a review is given about the effects of different parts of the solar radiation and its importance for plant growth in greenhouses. Besides the most important visible part of the light (PAR), ultraviolet (UV), near infrared (NIR) and far infrared (FIR) are discussed. The strength of the greenhouse structure can be calculated following the new European Standard for Greenhouses EN 13031-1. The orientation and the roof inclination at the greenhouse have limited influence on the light transmittance. The most important material properties of greenhouse cladding materials are presented for glass, plastic sheets (PMMA and PC) and plastic films (PE, PVC and ETFE). These properties can be modified in the different materials, which leads to improvements of the materials with respect to light transmission, heat transfer, condensation behaviour, etc. Some recent results of research of greenhouse cladding materials and structures are described, like `floating greenhouses¿, `closed greenhouses¿, ETFE membrane, a greenhouse for tropical lowland, zigzag-shape double PC-sheet and microstructural coated glass.

Fouling of the solid lying area in pig housing is undesirable for reasons of animal welfare, animal health, environmental pollution, and labor costs. In this study the influence of temperature on the excreting and lying behavior of growing-finishing pigs of different BW (25, 45, 65, 85, or 105 kg) was studied. Ten groups of 5 pigs were placed in partially slatted pens (60% solid concrete, 40% metal-slatted) in climate respiration chambers. After an adaptation period, temperatures were raised daily for 9 d. Results showed that above certain inflection temperatures (IT; mean 22.6°C, SE = 0.78) the number of excretions (relative to the total number of excretions) on the solid floor increased with temperature (mean increase 9.7%/°C, SE = 1.41). Below the IT, the number of excretions on the solid floor was low and not influenced by temperature (mean 13.2%, SE = 3.5). On average, the IT for excretion on the solid floor decreased with increasing BW, from approximately 25°C at 25 kg to 20°C at 100 kg of BW (P

Gaseous emissions (NH3, CH4, N2O, odor) were measured from a deep litter farming system for dairy cattle in the Netherlands (barn and outdoor manure storage). On average, 13.9 kg NH3 per cow were emitted from the barn on a yearly basis. In addition, the outdoor manure storage emitted 7.9 kg NH3 per cow per year. The emission of CH4 from the barn (enteric fermentation + deep litter) was, on average, 1.3 kg day− 1 per cow. Emissions from the manure heap 2 weeks after being placed into the field were factors 3–4 lower than the emissions from the animal house. Nitrous oxide emission from both the barn and the outdoor manure storage was low. Odor measurements at the animal house resulted in an average emission of 73 OUE s− 1 per cow.

Agriculture contributes significantly to the anthropogenic emissions of non-CO2 greenhouse gases methane and nitrous oxide. In this paper, a review is presented of the agriculture related sources of methane and nitrous oxide, and of the main strategies for mitigation. The rumen is the most important source of methane production, especially in cattle husbandry. Less, but still substantial, amounts of methane are produced from cattle manures. In pig and poultry husbandry, most methane originates from manures. The main sources of nitrous oxide are: nitrogen fertilisers, land applied animal manure, and urine deposited by grazing animals. Most effective mitigation strategies for methane comprise a source approach, i.e. changing animals’ diets towards greater efficiencies. Methane emissions, however, can also be effectively reduced by optimal use of the gas produced from manures, e.g. for energy production. Frequent and complete manure removal from animal housing, combined with on-farm biogas production is an example of an integratedon-farm solution. Reduced fertiliser nitrogen input, optimal fertiliser form,adding nitrification inhibitors,landdrainage management, andreduced landcompaction byrestricted grazing arethebestways to mitigate nitrous oxide emissions from farm land, whereas, management of bedding material and solid manure reduce nitrous oxide emissions from housing and storage. Other than for methane, mitigation measures for nitrous oxide interact with other important environmental issues, like reduction of nitrate leaching and ammonia emission. Mitigation strategies for reduction of the greenhouse gases should also minimize pollution swapping. # 2005 Elsevier B.V. All rights reserved.

In this trial, the effects of the forage feeding frequency on the waiting time prior to milking and the cowshed facility utilization by cows milked in an automatic milking unit (AMU) were studied. The feeding frequency was increased from two times per day to six times per day. It was found that the average waiting time per visit for cows using the AMU was reduced from 755 s to 351 s when the feeding frequency was increased. The daily number of visits (milking visit, failed milking visit and not qualified visit) to the AMU was not affected by the change in feeding frequency. It was also found that increasing the feeding frequency had a positive effect on utilization of the cowshed facilities, such as the occupation of the feeding fence, and on the cowshed facilities in the waiting area (cubicles) of the AMU.

In a co-operation project of Wageningen University (Wageningen UR), Agrotechnology & Food Innovations B.V. (A&F), Priva Hortimation B.V. and Hyplast N.V. (Belgium) a greenhouse for the future has been developed. The project has four lines, namely 1. lowering the energy demand, 2. using solar energy for heating (greenhouse as solar collector), 3. modifying climate control and dehumidification and 4. developing of the highly insulated greenhouse. This paper deals with the development of the so-called Solar Greenhouse, the structure and cladding material and the (natural) ventilation openings. The aspects that play an important role in the process of development of the greenhouse are the strength of the structure, the light transmittance, the material consumption and the expected greenhouse climate. The high demands for energy savings lead to a greenhouse covering with a high insulation value and at the same time a high light transmittance. Advanced materials like fluor polymer films in double or more layers with the space in between inflated have these qualities. The most perspective greenhouse geometry is a saw-tooth roof structure with roof inclinations of 200 and 300, a span width of 10m and a vertical opening of 2 m for natural ventilation. The module for the greenhouse is repeatable in both directions to a big area. Caused by the asymmetric geometry of the greenhouse (openings oriented on one side) the influence of the wind and wind direction is extensive

The reduction of labour cost is the major motivation to develop a system for robot harvesting of roses in greenhouses that at least can compete with manual harvesting. Due to overlapping leaves, one of the most complicated tasks in robotic rose cutting is to locate the stem and trace the stem down to locate the cutting position. Computer vision techniques like stereo imaging, laser triangulation, röntgen imaging and a new technique, called reverse volumetric intersection, are evaluated in this paper to determine which technique is most feasible for the task. Experiments with the techniques applied on different rose plant indicate that reverse volumetric intersection shows that this technique is most promising to locate the stem down to the cutting position in terms of robustness and costs.

Besides harvesting the fruits, a very time demanding task is removing old leaves from cucumber and tomato plants grown in greenhouses. To be able to automate this process by a robot, a leaf detection method is required. One possibility for the detection is to exploit the different dynamic behaviour of leaves and stems in case they are excited by mechanical impulse such as an airstream. The objective of this paper is to investigate this technique using a camera and image analysis. For the experiments carried out, images of a tomato crop were used. Images were taken with a digital camera from different distances. To generate an air stream, different radial blowers were used. A sequence of 5 digital images was recorded with a sample rate of 1 second with different settings. To find the differences between the images, the intensity of the images were mathematically subtracted. The resulting binary images were further processed with the aim to extract the leaf positions. These steps included automatic thresh-holding, noise reduction and morphological image analysis operations. It was found that moving objects in the images could be detected using the method described above. Budging objects could only successfully be traced if colour, intensity or structure of the moving object differed with the colour, intensity or structure of the background. The blowing direction had a strong influence on the movements. It is concluded that with this technique not only leaves can be detected but also other parts as e.g. fruits, stems and branches can be discriminated.

The scope of this investigation is the development of a new energy-saving greenhouse with a high light transmittance. With GE-Plastics a new Zigzag double-web structure is developed which combines energy saving and a high light transmission. The following factors were taken into account: light transmittance, insulation value, material consumed and material strength. The insulation value of the sheet was calculated according a European Standard method with a computational fluid dynamics (CFD) program. An extra advantage of these zigzag-sheets is that they can be built in without glazing bars. These double structures of ARM-glass or the Zigzag Lexan can just compensate the light losses caused by an extra layer. Therefore this material combines high light transmittance with good thermal insulation. With the simulation program ¿Kaspro¿ we can predict the year round energy consumption of greenhouses with hourly climate data. Different greenhouse constructors have build Venlo type greenhouses and also a wide span greenhouse

Water resources are diminishing in many (semi) arid regions, thus becoming a concern in the (near) future. Desalination of brackish or salt water can be a good solution to provide water for agriculture and human consumption. The Watergy project proposes an integrated system in which plants and fresh water are produced. The system is closed and air is being cooled during the day with a central heat exchanger in a chimney. Since this heat exchanger is a vital part for the functioning of the system, it was decided to test its characteristics such as heat transfer and air velocities in a controlled environment. A chimney was built with a heat exchanger installed inside with a surface of 11 m2. Several experiments were conducted with varying layout of the heat exchanger, varying conditions and excitation signals. This paper describes the results of steady state situation with five baffles during heating and cooling. The measured air velocities are in the range of 0.72 0.6 m/s. The measured heat exchange coefficient is in the range of 25 28 W/m2K. The efficiencies of all the presented experiments are in the range of 70 ¿ 80%. The results of the experiments are compared to a simple physics based, steady state model that describes the convection, conduction and condensation processes. The model results are quite close to the experimental results; the maximum temperature deviation between model and observations on the water-side is 0.5¿C (at 40¿C) and on the air side 2.5°C. The accuracy of the model is sufficient to use it for design purposes and, later on, as a starting point for model based control of the greenhouse. Finally, the results of the experiments show that the heat transfer in the proposed design can be sufficient to cool and heat the Watergy greenhouse.

Reliable and quick assessment of energy conservation measures in greenhouse cultivation supports growers in their operations. Such an overview should quantify the consequences of changes in energy flows for total energy consumption, amount and quality of production, and farm economy. Using tomato as an example crop, comprehensive energy balances were developed for a reference situation in The Netherlands. Solar radiation, primary and secondary heating circuits and CO2 from the flue gasses of the heating system were quantified as energy sources. Energy use for air and leaf temperature increase, crop photosynthesis, crop transpiration, as well as energy losses through the roof, walls and ground surface were quantified. Subsequently, the effects of 11 energy conservation measures were computed. Consequences for gas consumption and production were simulated with a greenhouse and a crop growth model, respectively, consequences for quality were assessed on the basis of expert knowledge, and economic consequences were simulated with a cost-benefit model. For tomato, most energy was saved by increased insulation of the greenhouse cover (23% saving) and lowered temperature set point (16%), followed by increased set point for air relative humidity, screen gap control in steps, and temperature integration (all about 5%). Fresh tomato production fell in most cases, except in case of increased light transmission by the greenhouse cover. Energy use efficiency was defined as the amount of energy required to produce a certain quantity of fresh harvestable product. Energy-conservation aims to decrease the energy use efficiency. Greatest gains were reached through insulation (-20%), lowered temperature set point (-12%) and improved light transmission (-8%). Improved light transmission resulted in the strongest increase of the balance of yield and costs (¿2.6, or 10%), followed by increase of RH set point, crop-based RH control, crop-based use of the energy screen, increased size of the thermal storage tank and reduction of crop transpiration (all less than ¿0.5). Although energy conservation reduces fuel costs, its implementation depends on the effects on production an overall economic profitability of the farm. Improved roof insulation, reduced temperature set point, screen gap control in steps, increase of the RH set point, temperature integration, and crop-based RH control are first candidates for (further) implementation. Other measures require prior technological advancements or fine-tuning

The WET-sensor is a frequency domain dielectric sensor that measures permittivity, conductivity and temperature, which can be used for monitoring soil water content and electrical conductivity in horticulture. By using a specific model it measures pore water conductivity as well. However, under practical circumstances, large errors have been observed using the existing model. The purpose of this study was to obtain a empirical correction for this model and to investigate the nature of the errors, so horticultural growers can use the WET-sensor to measure pore water EC in-situ. Using 36 potted samples of sand, clay and peat, the relation between permittivity, bulk EC and pore water EC was studied in a laboratory over a temperature range from 19-22 oC and a pore water EC range from 4 ¿ 12 mS/cm. This resulted in an adaptation of the constant in the existing model and an extra second order polynomial correction factor. After temperature correction, an overall linear fit with a coefficient of 0.9948 was found at a reasonable correlation (0.79). Errors may occur up to ±40%, but for permittivity values larger than 20, errors have a maximum of ±15%. The overall standard deviation is 15%, which is in accordance with simulated results. For growers using relatively wet soils at water contents above 20%, the WET-sensor can be used to measure pore water EC in situ with a reasonable accuracy. Further study is needed to explore this correction at larger temperature ranges and for more soil types

Improved housing for laying hens may start from the translation of their behavioral needs into welfare-based design parameters for laying hen houses. The objective of our research was to gain insights into the facility usage and behavioral needs of the hen over 24 h when there are no obvious restraints. Twenty ISA Brown commercial laying hens (Gallus domesticus) that were 18 wk old and not beak trimmed, were accommodated in a pen (4 x 6 m) at 19 + 2 degrees C on a light-dark cycle of 10L:14D. The pen providing nest boxes, drinkers, feeders, perches, sand, and wood shaving was designed to accommodate the hens for the experimental period. Video recordings were made for 10 d. Behavioral analyses were conducted on 5 birds for 5 d. Time spent on each behavior, log survivor analysis of events and inter-event intervals, bout analysis, diurnal pattern in events and bouts, occurrence of behavior in different segments and the corridor of the pen, and sequence analysis were performed to gain insights into the temporal and sequential structures of behavior. Hens spent 97% of the day on nest use, preening, drinking, feeding, still, walking, perching, and resting; 43% on commodity-dependent behavior; and 57% not on commodity-oriented behaviors. Behavioral events were short (around 70% event2 min) and frequent (around 70% inter-event intervals40s). The pen corridor was the preferred place for attack, escape, flying, resting, walking, and wing flapping. Feeding-drinking-feeding, preening-resting-preening, scratching-resting-scratching, dust bathing-resting-preening, or dust bathing-resting-wing stretching-dust bathing were the preferred sequences of behavior. Although hens interrupted ongoing behaviors and changed behaviors frequently, they nonetheless clustered behavioral events.

Removal of methane from exhaust air of animal houses and manure storage has a large potential for the reduction of greenhouse gas emissions from animal husbandry. The aim of this study was to design a biofilter for methane removal at a full-scale livestock production facility. Air from the headspace of a covered 6 m3 liquid manure storage (air flow: 0.75-8.5 m3 m(-3) h(-1); CH4: 500-5500 mg m(-3)) was treated in an experimental biofilter (160 L). The filterbed, a mixture of compost and perlite in a 40:60 (v/v) ratio, was inoculated with activated sludge that had shown a good methane oxidation rate as compared to pure cultures in preceding laboratory tests. Methane removal up to 85% could be achieved in the experimental biofilter. The methane removal (g m(-3) h(-1)) appeared to be proportional to the concentration (g m(-3)) with k = 2.5 h(-1). Relatively low methane concentrations and high air flows, as reported for the exhaust air of animal houses, would require very large biofilter sizes. Extrapolation of the results showed that treatment of air from a 1000 m3 liquid manure storage with a methane concentration of 22 g m(-3) would require a 20 m3 biofilter for a desired emission reduction of 50%. The costs for such a biofilter are USD 26 per t of CO2 equiv reduction.

In de biologische landbouw is de onkruidbestrijding een van de belangrijkste problemen. Vooral in de langzaam groeiende en weinig concurrentiekrachtige gewassen is veel handwiedwerk nodig. Er zijn verschillende machines om de onkruiden in de gewasrij aan te pakken. Onderzoek heeft zich gefocust op de mogelijkheden van achtereenvolgens eggen, torsiewieden, vingerwieden, wieden met lucht onder hoge druk (Pneumat) en een met sensoren uitgeruste schoffel. Knelpunt bij de mechanische onkruidbestrijding is de vernietiging van onkruid in de gewasrij bij jonge, tere gewassen. Ten opzichte van de eg zijn er de afgelopen jaren diverse verbeterde machines beschikbaar gekomen. De eerste intelligente wieder is inmiddels commercieel beschikbaar. In deze publicatie worden (on)mogelijkheden, innovaties en uitdagingen belicht

Adaptation of a greenhouse climate management strategy to local climate conditions is important for the improvement of resource use efficiency of greenhouse crop production. In this paper the optimal greenhouse climate management under hot, humid, subtropical summer conditions was investigated through simulation analysis based on the Greenhouse Process (KASPRO) model, previously validated under this particular conditions. The study was limited to affordable means of greenhouse design, crop and climate management such as ventilation capacity, canopy size and whitewashing, in a greenhouse without injection of carbon dioxide. Obviously, the increase of greenhouse ventilation capacity leads to an increase of carbon dioxide concentration in the greenhouse air, canopy transpiration, and thus evaporative cooling of the greenhouse air and crop canopy, and in turn to an increase of crop biomass production. The results show, however, that there is a rather sharp ceiling beyond which there is little gain in increasing ventilation capacity. For a cucumber crop under the summer conditions typical of Shanghai, the ventilation capacity of the greenhouse should be about 40 volume changes per hour. The balance of assimilation, respiration and evaporative cooling ensure that crop biomass production is maximal at a canopy leaf area index of 4.

The paper presents an information based systematic design method for robotics in greenhouses. The method was used to develop a de-leafing robot in a period of one year with a limited budget. This robot is used in this paper as a design example. This approach proved to be a success. The design methodology enabled the efficient design of a complex machine. Bottlenecks were identified at an early stage. The methodology produced insight into design alternatives, thus limiting trial and error. Within one year the de-leafing robot was tested in a greenhouse, with success.

An increasing fraction of protected cultivations is on systems where drain water is recollected and re-used for irrigation (closed systems). Such systems have a direct reward for growers in saving on fertilizers (and water) costs and in a higher value of the product, caused by a better control of the root environment. In view of the benefit of the prevention of leaching of chemicals in the environment, the application of closed irrigation systems is being increasingly made compulsory. However, when irrigation water contains non-nutrient salts, such salts will accumulate in the closed loop. Since a high salt concentration is known to cause yield loss (though the effect is specie-specific), first or later salts will have to be leached out, by draining the loop. Indeed, even in Holland (where environmental rules are possibly the strictest) growers are allowed to leach the system whenever a specie-specific ceiling of sodium concentration is reached. It can be shown that in a crop cycle, the fraction of water that is leached is nearly proportional to the ratio between the concentration of the critical salt of the irrigation water and the concentration at which the system is leached. In principle, therefore, the ¿optimal¿ EC-ceiling can be calculated, that balances marginal costs of water and fertilizers with marginal yield loss. By using a number of yield response curves, in a couple of different cases (Holland and Mediterranean basin), we show that, with realistic prices both of resources and of produce, the optimal EC is very near to the value that ensures maximal yield. That is, there is no advantage to the grower in maintaining a closed loop whenever the quality of irrigation water is poor. Therefore, closed systems are financially viable only in two cases: a. in regions with good water or b. with high-value crops that offset the costs of ensuring good water (such as rain collection or desalinization). We will show that the latter is the case in most protected cultivation in Europe. On the other hand, there is no way that low-value crops in poor-water-quality regions may still be profitable under stricter environmental rules. This means that local authorities, seriously planning to enforce such rules, should either provide incentives for growers to switch to less sensitive or more valuable combinations of crops, or contemplate developing other economic activities than agriculture.

Within the framework of the project SPECTRAFOIL funded by the EU and Grafe Color Batch (Germany), together with the industrial partners Palrig (Israel), Sunsaver (Spain) and several growers and research partners in Israel, Cyprus, Spain and The Netherlands, new fluorescent greenhouse films for several climates and several horticultural production systems were developed. One of the results of SPECTRAFOIL was the development of new blue fluorescent greenhouse films. Technical aspects were investigated, such as spectral light transmission, fluorescent effect, stability of pigments and films. The effect of different fluorescent films on the production and quality of strawberry fruits was investigated at A&F, Wageningen. In these experiments, strawberry plants were grown in small tunnels covered with films containing blue fluorescent pigments in different concentrations, which increased total light transmission and influenced light quality (more blue light) during the years 2002 and 2003. Both fruit production (number of fruits, fruit weight) and fruit quality (color, size, shape, dry matter, freedom from physiological disorders and diseases, balance between sugars and acids) were determined. Blue fluorescent films caused strawberry plants to produce a higher yield, a higher number of fruits and a slightly higher mean fruit size. Differences in fruit quality were small. Moreover, the effects of blue fluorescent films on different shrubs, perennials and annuals were tested at two growers in The Netherlands. Blue fluorescent films gave a 4 days earlier yield to Alchemilla and a 2 days earlier yield to Virburnum. Flower quality of Alchemilla was improved. This was probably due to higher day temperatures and lower humidity caused by a higher light transmission of the film. The same film caused a 5 days earlier yield to Celosia, at the same time improving flower quality. Blue fluorescent films have potentials to increase the yield of strawberry and force the flowering of perennials.

Doel van dit onderzoek is de ontwikkeling van een nieuwe energiebesparende kas met een hoge lichtdoorlaatbaarheid dat gebruik maakt van een nieuwe zig-zag, dubbele web structuur dat energiebesparing en hoge lichttransmissie combineert

Kennis van licht en warmte doorlatende eigenschappen van kasmaterialen biedt telers de mogelijkheid de beste keuze te maken voor hun productie. Een vergelijking tussen glastypen en plastics

The development and market introduction of affordable ion specific sensors, like the ISFET sensor, has paved the way for completely new systems for application of fertilisers to crops in greenhouses. This paper describes the use of information feedback from flow sensors and ion specific sensors to regulate the supply of water and nutrients to a model gully. When a controller keeps the drain flow and the concentrations of the individual ions in the drain at a sufficiently high fixed value, the uptake of the plants is intrinsically compensated, i.e. the demand of the plants is exactly satisfied. Time series measurements of flow and concentration in supply and drain are used to design the controller for applying nutrients to a tomato crop in a near-practice greenhouse. Data are shown of fertiliser concentrations and flow in supply and drain during the design phase and test phase of the controller.

The effects of relative humidity (RH) and high ambient temperature (T) on physiological responses and animal performance were studied using 12 groups (10 gilts per group) in pens inside respiration chambers. The microclimate in the chamber was programmed so that T remained constant within a day. Each day, the T was increased by 2°C from low (16°C) to high (32°C). Relative humidity was kept constant at 50, 65, or 80%. The pigs¿ average initial BW was 61.7 kg (58.0 to 65.5 kg), and their average ending BW was 70.2 kg (65.9 to 74.7 kg). Respiration rate (RR), evaporative water (EW), rectal temperature (RT), skin temperature (ST), voluntary feed intake (VFI), water-to-feed ratio (rW:F), heat production (HP), and ADG were analyzed. The animals had free access to feed and water. We determined the T above which certain animal variables started to change: the so-called inflection point temperature (IPt) or "upper critical temperature." The first indicator of reaction, RR, was in the range from 21.3 to 23.4°C. Rectal temperature was a delayed indicator of heat stress tolerance, with IPt values ranging from 24.6 to 27.1°C. For both these indicators the IPt was least at 80% RH (P

Risk factors concerning both the pasture and housing seasons for interdigital dermatitis and heel-horn erosion (IDHE) were studied in dairy cows in a cross-sectional study in The Netherlands. The study population included 2326 cows (41 herds) and 2751 cows (46 herds) for the pasture and housing seasons, respectively. Of these animals, 545 (23%) showed serious lesions of IDHE (stages 2 and 3) at the end of the pasture season and 1269 (46%) during housing. Logistic regression of the pasture study indicated that increased parity, solid concrete floor, restricted grazing time, and herd trimming at long intervals were associated with an increased odds of IDHE, while dry cows and lactating cows within 30 days after calving as well as cows on a slatted floor with manure scraper, and grassland with mixed type of soil were associated with lower odds. In the housing study, odds of IDHE increased with parity, administering low- or medium-energy roughage, and introduction of dry cows into the lactating herd at >2 weeks before calving. The presence of long cubicles, knee-bumpers installed in cubicles as well as rearing calves and heifers within the dairy cows’ accommodation decreased the odds of IDHE.

Altering environmental factors may change odor emission from pig manure. The main objective of this laboratory-scale study was to examine the effects of temperature, ventilation rate, emitting area, and manure dilution ratio on odor emission from growing pig manure, while also testing their effects on manure characteristics. Manure was placed in vessels with different surfaces (303, 475, and 595 cm2), and water was added to create different dilution ratios (0%, 50%, and 100%). The vessels were connected to glass capillaries with different ventilation rates through the headspace (0.5, 1.0, and 1.5 L min-1) and were placed in climate-controlled rooms with different temperatures (10°C, 20°C, and 30°C). We used a face-centered central composite design with 54 experimental units in two rounds of three blocks. Odor samples were taken at the end of experiment (after seven days). Manure samples were collected at the start and at the end of the experiment. The mean odor emission from the manure vessel was 2326 ouE h-1 m-2. Increased temperature, ventilation rate, and dilution ratio increased odor emission. Emitting area did not influence odor emission, but positively influenced total-N loss. Total-N loss increased as temperature and ventilation rate increased, but decreased as dilution ratio increased. Lowering temperature and ventilation rate can be considered as starting points to reduce odor emission from pig manure in practical conditions. The effects of dilution ratio and emitting area on odor emission could not be fully separated from the effect of headspace volume in this study and should be further studied.

Several claw shape measurements, horn hardness, and horn growth and wear were recorded monthly at 12 dairy farms to investigate the effect of floor type and changes in these traits over time. Herds were either housed on a slatted floor (SL), solid concrete floor (SC), grooved floor (GR), or on a straw yard (SY). Twenty cows per farm were selected and stratified by parity. Information on claw traits was recorded on right lateral hind claws between October 2002 and May 2003. In addition, lesion development of interdigital dermatitis and heel erosion (IDHE) and digital dermatitis (DD) was studied in both rear feet. No differences in claw traits were detected among groups on different floor types, with the exception of claw angle. Claw angles were smallest in cows on SY. Claws of cows on SC were steeper than those on SL and GR. The study provided no evidence that floor-related differences in claw lesions were related to differences in horn growth, wear, and resulting claw shape. Lesions of IDHE developed gradually over time and did not differ among flooring types. Cows in SY had the smallest lesion scores for DD, whereas cows on SL had significantly less DD than cows on SC and GR. Incidence of DD fluctuated over time. Development of different stages of DD was monitored in-depth. Both early and healed stages were rather changeable and often turned into other disease stages. Classical ulcerative lesions (stage M2) persisted for a long time, with 20% of the initially unaffected claws having active lesions of DD within 5 mo. The M2 lesions generally did not cure effectively after claw trimming, and frequent use of footbaths resulted in a poor prognosis for recovery.

In 2003 is een vierjarig project gestart met als doel de optimalisatie van de bijdrage van groenbemesters aan het onkruidbeheer in biologische teeltsystemen. Groenbemesters kunnen een belangrijke rol spelen in de vruchtwisseling en een hoge toegevoegde waarde hebben. In het najaar kan een goed ontwikkeld groenbemestinggewas de groei, ontwikkeling en de zaadproductie van onkruiden tegengaan. In de winter en het vroege voorjaar kan de geproduceerde biomassa worden ingewerkt in de bodem en als gevolg van allelopatische en/of fysische effecten mogelijk de kieming, vestiging en vroege groei van onkruiden onderdrukken. In deze publicatie wordt een overzicht gegeven van de verschillende onderzoeksactiviteiten.

The objective of the solar greenhouse project was the development of a Dutch greenhouse system for high value crop production without the use of fossil fuels. The project was completed and the results are reported here. The main approach was to first design a greenhouse system requiring much less energy, next to balance the availability of natural energy with the system's energy demand, and finally to design control algorithms for dynamic system control. This paper discusses the first two design steps. Increasing the insulation value of the greenhouse cover was the first step towards a reduction in energy demand. The challenge was in maintaining a high light transmission at the same time. A first generation of suitable materials was developed. The realizable energy saving is almost 40 %. The next reduction in fossil fuel requirement was accomplished by capturing solar energy from the greenhouse during the summer months, storing it in an underground aquifer at modest temperatures, and finally using the stored energy during the winter months by using heat pumps. Then the total realizable energy saving is more then 60%. For sustainable energy supply per ha greenhouse at this low energy demand 32 ha biomass is needed, or 600 kW nominal wind power or 1.2 ha PV assuming storage via the public grid.

Acid scrubbers and biotrickling filters have been developed for ammonia (NH3) removal at pig and poultry houses in The Netherlands over the last 20 years to prevent acidification and eutrophication of soils. Because of growing suburbanization, odor removal is increasingly considered important as well. In this review, we report the results of the on-farm research on full-scale operated scrubbers for treatment of exhaust air from animal houses with regard to NH3 and odor removal in The Netherlands. The NH3 removal of acid scrubbers ranged from 40% to 100% with an overall average of 96%. The NH3 removal of biotrickling filters ranged from -8% to +100% with an overall average of 70%. Minimum empty bed air residence times (EBRTs) were 0.4 to 1.1 s. For acid scrubbers, process control with pH measurement and automatic water discharge is sufficient to guarantee sufficient NH3 removal. For biotrickling filters, however, improvement of process control is necessary to guarantee sufficient NH3 removal. The odor removal of acid scrubbers ranged from 3% to 51% with an overall average of 27%. The odor removal of biotrickling filters ranged from -29% to +87% with an overall average of 51%. Minimum EBRTs were 0.5 to 2.3 s. Further research is necessary to explain this variation and to improve the odor removal efficiency of both acid scrubbers and biotrickling filters.

In Maribor, Slovenië, werd van 11-15 februari 2004 het 13e internationale symposium over kreupelheidsproblemen bij herkauwers gehouden, waarvan de 10 sessies hier worden samengevat

In this study results are presented of investigations on the development of a cucumber crop in a closed rockwool system and on the potential change in microbial suppressiveness due to different disinfection methods after inoculating part of the plants with the fungal pathogen Pythium aphanidermatum. Two trials were executed at which the core treatments were disinfection (UV, slow filtration and no disinfection as control), while additional treatments were priming half of the systems before planting either with an 'old' nutrient solution from a former cucumber crop (spring trial) or an actinomycetes suspension (autumn trial). Crop developments (yield, disease and root development) and composition of the microflora were recorded. Non-inoculated plants showed that disinfection is needed either with UV or slow (sand) filtration to avoid spread of the pathogen; yield and root development was better and disease symptoms were less compared to the control. The hypothesis that passive disinfection might realise a more suppressive environment against Pythium aphanidermatum could not be proved, since inoculated plants showed a similar yield, disease and root development after the different disinfection treatments. Priming the nutrient solution with an 'old' solution did not show significant differences in the composition of the microflora either by plate-counts or by PCR-DGGE. However, the addition of actinomycetes before planting resulted a 100 to 1000 fold increase of the actinomycetes population in the cropping system up to the end of the trial. In the spring trial, differences within the microflora as a result of the disinfection treatments were only detected for pseudomonads. In the autumn trial, differences in numbers of pseudomonads, actinomycetes and fungi were significant in the treated nutrient solution, but not in the drain. With PCR-DGGE, differences in the bacterial profile were detected in autumn in both the drain and treated solution; i.e. less bands (corresponding to certain bacterial species) occurred in the UV treatment compared to slow filtration and control

Air treatment with a compact biological membrane filter, and air quality monitoring with an electronic nose were tested in the laboratory on air from a cage containing six mice. Additional analyses of air to and from the filter were performed using olfactometry and ammonia and hydrogen sulphide gas detection tubes. The biological air filter is a module containing biofilm-coated membrane fibres that separate a closed liquid loop from a gas phase. Odour compounds and oxygen diffuse through the membranes from the gas phase to the biofilm, where they are degraded to carbon dioxide and waterAir treatment with a compact biological membrane filter, and air quality monitoring with an electronic nose were tested in the laboratory on air from a cage containing six mice. Additional analyses of air to and from the filter were performed using olfactometry and ammonia and hydrogen sulphide gas detection tubes. The biological air filter is a module containing biofilm-coated membrane fibres that separate a closed liquid loop from a gas phase. Odour compounds and oxygen diffuse through the membranes from the gas phase to the biofilm, where they are degraded to carbon dioxide and water. The prototype "ENOBE" electronic nose is based on an array of eight thickness shear mode resonators (TSMR), also known in the literature as quartz microbalance sensors. The chemical sensitivity is given by molecular films of metalloporphyrins and similar compounds. Chemical interaction of compounds in the air with the vibrating sensors induces a frequency change of the vibration that can be measured as a signal. The air from the mouse cage had a strong odour (3490 OUE/m(3)). The biological membrane filter performed well, achieving over 80% odour and ammonia reduction. The electronic nose signal could be correlated with the inlet and outlet air-quality of the biological filter, making it a promising method for monitoring air quality in closed environments.

New technologies are needed for manure treatment that can capture nutrients, reduce emissions of ammonia and nuisance odours, and kill harmful pathogens. A reactor concept was developed for simultaneous treatment of separately collected liquid and solid fractions of pig manure. The liquid fraction is concentrated by evaporating the water using energy from the composting system and at the same time scrubbing ammonia from the composting off-gas by acidifying the urine to pH 4 with nitric acid. This results in two marketable products, a concentrated liquid nitrogen fertiliser (NH4NO3) without phosphorus, and a stabilised, solid organic fertiliser, which is free of pathogens and weeds. By connecting the two reactor systems, emissions of ammonia and odours are abated as ammonia emitted from the composting is trapped in the liquid fraction and odorous compounds emitted from the liquid are degraded in the composting reactor. The concept was physically simulated by coupling a 80-L compost reactor to a 10-L bubble column. Operation of the bench-scale system showed that the concept is very promising. All nutrients were captured, and emissions of ammonia and odours were almost completely abated.

The hypothesis that water flow into tomato fruits is affected similarly by osmotic potential of the nutrient solution and potential transpiration (shoot environment) via their effects on stem water potential, was tested through experiments carried out in two glasshouses where climate was controlled to maintain a desired potential transpiration rate (normal and depressed, respectively). This climate treatment was factorially combined with a root zone osmotic potential treatment, whereby two values of osmotic potential were compared in each experiment. Data showed that water uptake per unit leaf area was not affected by osmotic potential of the nutrient solution. The hydraulic resistance within the plant, deduced from measurements of leaf and stem water potential, was independent of the transpiration flow and was not affected by the osmotic potential of the nutrient solution. Water import into the fruit was affected by both treatments and was correlated with the water potential gradient between the stem and the fruit. Since fruit osmotic potential was relatively constant at a given concentration of the nutrient solution, the stem water potential appeared to be a good indicator of fruit growth rate.

Given that exposing rapidly growing pigs to high ambient temperatures can induce heat stress, which reduces their welfare and production, this study looked at the influence of floor cooling on pigs¿ behavior and performance. Pens in room 1 had a solid floor (60%) and a metal slatted floor (40%). The pens in room 2 had a concrete slatted floor at the front (15%), then a convex solid floor (45%), and a metal slatted floor at the back (40%). Each room was stocked with 144 pigs with a starting weight of around 29.3 kg (±4.1 kg). The area per pig was approximately 1.0 m2. In half of the pens in each room, the floor could be cooled by cold water. The floor cooling was activated at ambient temperatures above 25°C in week 3 and above 20°C from week 7 onwards. Feed and water were accessible ad libitum. Cooling lowered the surface temperature of the solid floor (25.0°C vs. 26.8°C, P

Sustainable agriculture is an important issue in the Netherlands. A balance between People, Planet and Profit is necessary to create a sustainable agriculture. Entrepreneurial qualities are important for farmers to find this balance for his particular situation. Therefore, three research institutes of Wageningen UR have started a joint project to analyse and develop entrepreneurship in agriculture, being started in 2002 and ending in 2005. This project is linked to several existing farmers networks, in which farmers are facilitated through research to develop organic or integrated agriculture. Entrepreneurship of co-operating farmers was analysed through a questionnaire, resulting in an overview of strengths and weaknesses. Through this, topics were identified for improvement of specific entrepreneurial qualities through participatory work. The results showed a generally low score on farm management and strategic planning, relationship with personnel and personnel management, information seeking and finding, learning and networking, and personal characteristics. In 2003 five participatory projects were started. Farmers were invited to participate in these projects. The projects existed in two or three meetings and farmers had to do some homework in between. Various analysis and simulation tools were used. Farmers received a report, in which individual results were compared with the group average. In 2004, all projects will get a second round and a new project about ‘employership’ will be set up. Monitoring and evaluation is an important issue in this project, to improve both the content and the process of the participatory projects. The lessons learned can also be translated into a training for advisors or into an educational course. The questionnaire is a useful tool for analysis of entrepreneurship and will be transformed to an internet tool for farmers. The participatory approach seems to be a fruitful method to improve entrepreneurial qualities of farmers.

Several recent studies in juvenile pigs demonstrated a relationship between the degree of resistance displayed early in life in a so-called "backtest" and parameters of cell-mediated and humoral immunity. Some of the immune characteristics were reported to depend on the interaction between backtest classification and housing system. In the present study, the effects of backtest classification and housing condition on immune reactivity in adult gilts were examined. At 10 and 17 days of age, female piglets were subjected to the backtest. In this test, each piglet is restrained on its back for 1 min and the number of escape attempts is scored. Pigs classified as high resisting (HR) or low resisting (LR) were selected and housed in groups of six gilts. At 7 months of age, half of the gilts were housed in individual stalls. At 12 months of age, gilts were challenged by immunization with DNP-KLH. Control gilts were treated similarly with a placebo. Blood samples were drawn prior to immunization (Day 0) and weekly thereafter until Day 28. No significant effects of backtest type on cellular and Immoral responses against KLH were found. Furthermore, being housed in stalls as compared to groups had no consequences for the immune response and did not induce differences between HR and LR gilts. Differences in behavior and physiology found previously between HR and LR gilts, particularly in gilts in stall housing, may thus be of relatively little importance for immune-related health. (C) 2003 Elsevier Inc. All rights reserved.

Claw health was examined in an observational study on Dutch dairy farms with either a slatted floor (SL), slatted floor with manure scraper (SL-SCR), solid concrete floor (SCF), a straw yard (SY), or a zero-grazing feeding system (ZG). Hooves of cows' hind legs were examined for the presence and severity of claw disorders during hoof trimming events at the end of the pasture (P-study) and housing period (H-study). The number of cows in each study was 3078 (49 herds) and 3190 (47 herds), respectively. Due to a different hoof trimming strategy, data collected during both observation periods in SY herds (638 cows; 16 herds) were combined. Cows in straw yards (SY) had by far the lowest numbers of claw disorders. Over 80% of cows exposed to concrete flooring had at least one claw disorder at the time of observation, whereas on SY surfaces, this percentage was between 55 and 60. Cows on SL-SCR were less frequently affected by interdigital dermatitis/heel erosion (IDHE) and digital dermatitis (DD) than cows on SL (reference floor system). Little difference in claw health was found between SF and SL. The ZG cows were at higher risk (OR > 2) for most claw disorders in the P-study, whereas in the H-study, ZG cows showed less IDHE, sole hemorrhage, and sole ulcer. All herds on concrete flooring (SL, SL-SCR, SCF, ZG) were infected by DD, resulting in an average cow level prevalence of 30%. This indicates that the level of DD infection has increased considerably over the last 10 yr in The Netherlands.

The soil tare of sugar beet from wet clay soils should be reduced to lower the cost and prevent some negative effects of soil tare. Commonly used share lifters press the soil onto the sugar beet and, thereafter, the soil adheres strongly to the beet and is difficult to remove from the beet by mechanical cleaning systems. With the objective to reduce adhering-soil tare and soil adherence, a grab lifter (extraction, three variants) and a driven rotary-shoe lifter were compared with a conventional driven polder share lifter in a field experiment on clay soil. Soil tare after quick extraction with a small-pitch, spiral motion was reduced by a factor of 3.8-6.2, depending on the wetness of the soil. Relative soil adherence was reduced by a factor of 1.5. Soil tare after lifting with a driven rotary-shoe lifter was reduced by a factor of 3.7, irrespective of the soil wetness. Relative soil adherence was not reduced. For both uprooting methods, dug losses were slightly higher and superficial beet damage was lower compared to share lifting. While complex engineering and crown fracture hinder practical application of grab lifting, the driven rotary-shoe lifter offers good potential for reduction of soil tare in practice. (C) 2003 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd.

Emissions to the air and nutrient losses to the environment (ground water and soil) are inherent to the keeping of animals in high densities in animal houses and cause various problems to men and animal (environmental, health and nuisance). Traditional approaches in animal husbandry, and also the approaches to solve these problems, are often and primarily based on unidirectional technical solutions, in which control is exclusively exerted over both dead matter and living entities. As a consequence, each technical solution to a problem implies increased constraints for the animals involved or end-of-pipe solutions. A novel approach is presented to combine the nature of animals with the prevention and reduction of environmental pollution based on recursive control. This approach is based on the presence, knowledge and use of the natural behaviour of animals and their interrelation in the population. It is claimed that order in complex systems like these can be the result of animal interactions with their environment as well, without detailed human and technical intervention and surveillance. A fundamental precondition for this is a considerable degree of slack, or play, in order to give animals the latitude to adapt to changing local circumstances in the animal house. In this paper, we will outline and discuss this approach both theoretically and practically, using examples with elements that support the theory, like a straw-based group housing system for sows, an aviary housing system for laying hens, and the approach taken by a new concept for the keeping of fattening pigs (Hercules project). We end by drawing some general conclusions on the consequences of this approach for systems design and suggest a number of recommendations for design heuristics.

Bij het bouwen van een nieuwe kas, staat de boomkweker voor de keuze: glas of folie? De keus kan hij baseren op talrijke beoordelingscriteria. Wageningen UR zet de balangrijkste op een rij.

De toepassing van gewasbeschermingsmiddelen bij teelt onder glas. Onderzocht werden de effecten van druk en druppelgrootte op effectiviteit van bespuiting en belasting voor het milieu door verspilling

Biologische reiniging van baggerspecie door landfarming in combinatie met wilgenteelt wordt sinds 1997 toegepast door de Oostwaardhoeve te Slootdorp (Wieringermeer). Het perspectief van landfarming in combinatie met wilgenteelt wordt besproken. Geconcludeerd wordt dat anno 2005 landfarming van baggerspecie nog steeds een interessante optie is, maar dat wilgenteelt voor landfarming van olieverontreinigde species minder geschikt lijkt en voor langdurig te reinigen PAK verontreinigde specie alleen aantrekkelijk is, als enige financiële opbrengst uit de wilg gerealiseerd kan worden.

In deze brochure worden 20 gewassen gepresenteerd en wordt een selectie gegeven van enkele mooie rassen met bijbehorende – al dan niet sterke – verhalen. Het is een uitnodiging aan potentiële gebruikers de Oranje Lijst database te bezoeken.

In deze brochure worden 20 gewassen gepresenteerd en wordt een selectie gegeven van enkele mooie rassen met bijbehorende – al dan niet sterke – verhalen. Het is een uitnodiging aan potentiële gebruikers de Oranje Lijst database te bezoeken.